A Philosopher, who studies the art of dying, is in some measure astonished at the multiplicity of new objects which it affords; every step presents new difficulties and obscurities, without hopes of any instruction from the common workmen, who seldom know more than facts and custom. Their manner of explaining themselves, and their common terms, only afford more darkness, which the uncommon and often useless circumstances of their proceedings render more obscure.
Before we enter into the particulars of dying wool, it is necessary to give an idea of the primary colours, or rather of those which bear this name by the artists; for it will appear by reading the celebrated works of Sir Isaac Newton on Light and Colours, that they bear no affinity with those which the Philosophers call by that name. They are thus named by the workmen, because, by the nature of the ingredients by which they are composed, they are the basis from whence all others are derived. This division of colours, and the idea which I intend to give of them, are also common to the different kinds of dying.
The five primary colours are blue, red, yellow, brown and black. Each of these can furnish a great number of shades, from the lightest to the darkest; and from the combination of two or more of these different shades, arise all the colours in nature. Colours are oftentimes darkened, or made light, or considerably changed, by ingredients that have no colour in themselves; such are the acid, the alkalis, and the neutral salts, lime, urine, arsenic, alum, and some others; and in the greatest part of dyes, the wool and woollen goods are prepared with some of these ingredients, which of themselves give little or no colour. It may easily be conceived what an infinite variety must arise from the mixture of these different matters, or even from the manner of using them; and what attention must be given to the minutest circumstances, so as perfectly to succeed in an art so complicated, and in which there are many difficulties.
It is not needful to be very particular in describing the utensils of a dye-house, as they are commonly known; this work being designed for the experienced Dyer. A dye-house should, however, be erected on a spacious plan, roofed over, but admitting a good light, and as nigh as possible to a running water, which is very necessary, either to prepare the wool before it is dyed, or to wash it afterwards. The coppers should be set at the distance of eight or ten feet, and two or more vats for the blue, according to the quantity of work that is to be carried on.
The most important point in dying the primitive blue is to set the vat properly at work, and conduct her till she is in a state to yield her blue. The size of the woad vat is not fixed, as it depends upon necessity or pleasure. A vat containing a hogshead, or half that quantity, has often been used with success; but then they must be prevented by some means from cooling too suddenly, otherwise these small vats will fail.
Another kind of vat is prepared for blue: this is called the indigo vat, because it is the indigo alone that gives it the colour. Those that use the woad vat do not commonly use the indigo one.
There are two methods of dying wool of any colour; the one is called dying in the great, the other in the lesser dye. The first is done by means of drugs or ingredients that procure a lasting dye, resist the action of the air and sun, and are not easily stained by sharp or corrosive liquors. The contrary happens to colours of the lesser dye. The air fades them in a short time, more particularly if exposed to the sun; most liquors stain them, so as to make them lose their first colour. It is extraordinary that, as there is a method of making all kinds of colours by the great dye, the use of the lesser should be tolerated; but three reasons make it difficult, if not impossible, to prevent this practice.
1st, The work is much easier. Most colours and shades which give the greatest trouble in the great, are easily carried on in the lesser dye.
2d, Most colours in the lesser are more bright and lively than those of the great.
3d, For this reason, which carries more weight, the lesser dye is carried on much cheaper than the great. This is sufficient to determine some men to do all in their power to carry it on in preference to the other. Hence it is that the true knowledge of chymistry, to which the art of dying owes its origin, is of so much use.
It may be observed, that all lasting colours are called colours of the great, and the others of the lesser dye. Sometimes the first are called fine, the latter false colours; but these expressions are equivocal, for the fine are sometimes confounded with the high colours, which are those in whose composition cochineal enters; therefore, to avoid all obscurity, I shall call the first colours of the great, and the latter colours of the lesser dye.
Experiments, (which are the best guides to natural philosophy as well as arts) plainly shew, that the difference of colours, according to the foregoing distinction, partly depends on the preparation of the subject that is to be dyed, and partly on the choice of the ingredients which are afterwards used to give it the colour. I therefore think it may be laid down as a general principle, that all the invisible process of dying consists in dilating the pores of the body that is to be dyed, and depositing therein particles of a foreign matter, which are to be detained by a kind of cement which prevents the sun or rain from changing them. To make choice of the colouring particles of such a durability that they may be retained, and sufficiently set in the pores of the subject opened by the heat of boiling water, then contracted by the cold, and afterwards plaistered over with a kind of cement left behind with the salts used for their preparation, that the pores of the wool or woollen stuff ought to be cleansed, enlarged, cemented, and then contracted, that the colouring atom may be contained in a lasting manner.
Experiments also show that there is no colouring ingredient belonging to the great dye which has not more or less an astringent and precipitant quality. That this is sufficient to separate the earth of the alum; this earth, joined to the colouring atoms, forms a kind of laque, similar to that used by the painters, but infinitely finer. That in bright colours, such as scarlet, where alum cannot be used, another body must be substituted to supply the colouring atoms (block-tin gives this basis to the scarlet dye). When all these small atoms of earthy-coloured laque have insinuated themselves into the pores of the subject that is dilated, the cement which the tartar leaves behind serves to masticate these atoms; and lastly, the contracting of the pores, caused by the cold, serves to retain them. It is certain that the colours of the false dye have that defect only because the subject is not sufficiently prepared; so that the colouring particles being only deposited on its plain surface, it is impossible but the last action of the air or sun must deprive them of part, if not of the whole. If a method was discovered to give the colouring parts of dying woods, the necessary astriction which they require, and if the wood at the same time was prepared to receive them, (as it is the red of madder) I am convinced, by thirty experience, that these woods might be made as useful in the great, as they have hitherto been in the lesser dye.
What I have said shall be applied in the sequel of this Treatise, where I shall show what engaged me to use them as general principles.
I should have been glad to have seen a work of this sort, (knowing the great need there is of a chymical understanding of this art) signed with the name of some person of distinction, to have given it a better face; yet, in defect of that, I was prevailed upon to undertake the tedious task. I dare not flatter myself to have brought it to its last perfection, as arts daily improve, and this in particular; but I hope some acknowledgment will be due to me for bringing this matter a little further out of that obscurity in which it has hid, and for assisting the Dyers in making discoveries to help to perfect this most useful art.
I shall now proceed to examine the five primary colours above mentioned, and give the different methods of preparing them after the most solid and permanent manner.
JAMES HAIGH.
Dying is performed by means of Limes, salts, waters, leys, fermentations, macerations, &c. It is certain that dying is very ancient. The Chinese pretend that they owe the discovery of it to Hoan-ti, one of their first sovereigns.
One of the most agreeable effects of the art of dying, is the diversifying the colours of stuffs. There are two ways by which this agreeable variety is produced, either by needle-work with threads of different colours, on a uniform ground, or by making use of yarn of different colours in the weaving.
The first of these inventions is attributed to the Phrygians, a very ancient nation; the last to the Babylonians. Many things incline us to think that these arts were known even in the times of which we are now treating. The great progress these arts had made in the days of Moses, supposes that they had been discovered long before. It appears to me certain, then, that the arts of embroidery or weaving stuffs of various colours, were invented in the ages we are now upon. But I shall not insist on the manner in which they were then practised, as I can say nothing satisfactory upon that subject.
Another art nearly related to that of dying, is that of cleaning and whitening garments, when they have been stained and sullied. Water alone is not sufficient for this. We must communicate to it, by means of powders, ashes, &c. that detersive quality which is necessary to extract the stains which they have contracted. The ancients knew nothing of soap, but supplied the want of it by various means. Job speaks of washing his garments in a pit with the herb borith. This passage shows that the method of cleaning garments in these ages, was by throwing them into a pit full of water, impregnated with some kind of ashes; a method which seems to have been very universal in these first times. Homer describes Nausicaa and her companions washing their garments, by treading them with their feet in a pit.
With respect to the herb which Job calls borith, I imagine it is salworth. This plant is very common in Syria, Judea, Egypt, and Arabia. They burn it, and pour water upon the ashes. This water becomes impregnated with a very strong lixivial salt, proper for taking stains or impurities out of wool or cloth.
The Greeks and Romans used several kinds of earths and plants instead of soap. The savages of America make a kind of soap-water of certain fruits, with which they wash their cotton-beds and other stuffs. In Iceland the women make a ley of ashes and urine. The Persians employ boles and marls. In many countries they find earths which, dissolved in water, have the property of cleaning and whitening cloth and linen.
All these methods might perhaps be practiced in the primitive ages. The necessities of all mankind are much the same, and all climates present them with nearly the same resources. It is the art of applying them, which distinguishes polite and civilized nations from savages and barbarians.
As to wool in the fleece, which is used in manufacturing cloth, as well the mixt as other sorts, and which they are obliged to dye before they are spun, they are prepared in another manner, viz. they are scoured, and thereby divested of the natural fat they had when on the body of the animal * As this operation is properly the Dyer's , and is indispensable in wool which is to be dyed before it is spun, let the colour be what it will, I shall give the proper process.
This operation is not every where alike, but this is the method followed in the manufactory of Audly in Normandy, where cloths are most beautifully manufactured.
A copper containing twenty pails is used for this purpose; they put in twelve pails of water, and four of urine, (which is generally fermented) the copper is heated, and when the liquor is so hot as to bear the hand without scalding, ten or twelve pounds of wool, that still continues its natural fat, are put in and left in the copper about a quarter of an hour, stirring from time to time with sticks; it is then taken out and put to drain on a scray; from thence it is carried in a large square basket, and placed in running water, two men stirring it to and fro for a considerable time with long poles, till it is entirely cleansed of its fat; then it is taken out and placed in a basket to drain; while this wool is thus preparing, a like quantity may be put into the copper, and thus proceed till the whole is scoured. If the liquor is too much wasted, fresh is to be added, made up of one part urine and three parts water. They generally scour a bale of wool at once; if it weighed 250 lb. in the fat, it generally loses 60 lb in scouring; but this diminution of weight varies in proportion to the wool being more or less scoured, and in proportion to the more or less fat contained therein. Too much attention cannot be paid to the scouring, as it is thereby better disposed for the reception of the dye.
The fat, which is an oily transudation, and slightly partaking of the quality of urine retained by the fleece, which is too thick to let it out, is soluble in water, consequently, as water alone could not separate it, a fourth part of urine is put into the copper, which must have been kept some days, in order to separate the volatile salts by fermentation; (I mean that it is necessary this urine should begin to acquire a strong smell) this volatile salt, being an alkali, forms with the fat a kind of soap, which is always the result of all oils and alkalis whatsoever mixed together. As soon as soap is formed by the combination of these two principles, it becomes soluble in water, and is consequently easily carried off. A proof that a true soap has been formed in this operation, is, that the water which carries it away, whitens as long as any fat is separated from the wool; if there was a sufficient quantity of fermented urine in the copper, the wool will be well scoured; if it was not, all the fat would not be changed into soap, and consequently the wool will remain greasy. The same operation might be performed with fixed alkalis, as with the lee of pot-ash or pearl-ashes: but as the lee would not only come dearer than urine, it might also damage the wool, if the exact proportion was not applied. I am convinced by several experiements, that the caustic salts do easily destroy all animal substances, as wool, silk, &c.
I beg the reader may take notice, that though in the sequel I do not mention this operation of scouring, it is nevertheless necessary for all wool that is to be dyed before it is spun, as also that it is necessary to wet those that are spun, and stuffs of all kinds, that the colour may be the more equally diffused throughout.
Of the five primary colours mentioned in the Preface, two of them require a preparation given by noncolouring ingredients, which, by the acidity and fineness of their earth, dispose the pores of the wool to receive the colour. This is called the preparation; it varies according to the nature of shades and colours: the red, the yellow, and the colours derived from them must be so treated; black must have a preparation peculiar to itself; blue and brown require none; it is sufficient that the wool be thoroughly scoured and wetted; and even for blue, it suffices to dip it into the vat, stirring it well, and letting it remain, more or less, according as the ground of the colour is wanted. For this reason, and also that many colours previously require a blue shade to be given to the wool, I shall begin with it, and give thereon the most exact rules in my power. It is an easy manner to dye wool blue, when the vat is once prepared, but it is not easy to prepare the vat, which is the most difficult part of the Dyer's art. In all the other processes, it is sufficient to follow the simple operations transmitted from masters to apprentices. Three ingredients are used in the blue dye, viz. garden-woad or pastel, the woad, and the indigo. I shall give the preparation of each, beginning with the garden-woad.
The Vat set to Work.
A copper, as near as possible to the vat is filled with water that has stood some time, or, if such water is not at hand, a handful of Dyer's woad or hay is added to the water, with eight pounds of crust of fat madder. If the old liquor from a vat that has been used in dying from madder can be procured, it will save the madder, and produce a better effect.
The copper being filled, and the fire lighted about three in the morning, it must boil an hour and a quarter, some Dyers boil it from two hours and a half to three; it is then conveyed by a spout into the woad vat, in which has been previously put a peck of wheaten bran. Whilst the boiling liquor is emptying into the vat, the balls of woad must be put one after another into the vat, that they may be the easier broken, raked, and stirred; this is to be continued till all the hot liquor from the copper is run into the vat, which, when little more than half full, just be covered with cloths somewhat larger than its circumference, so that it may be covered as close as possible, and left in this state for four hours. Then it must be aired, that is, uncovered to be raked, and fresh air let into it; and to each bale of woad, a good measure of ware flung in; this is a concealed name for lime that has been slacked. This measure is a kind of wooden shovel, which serves to measure the lime grossly; it is five inches broad and three inches and a half long, containing near a good handful; the lime being scattered in, and the vat well raked, it must be again covered, leaving a little space of about four fingers open, to let in air. Four hours after, she must be raked, without serving her with lime; the cover is then put on, leaving, as before, an opening for the air; in this manner she must be let to stand for two or three hours. Then she may be raked well again, if she is not yet come to work; that is, if she does not cast blue at her surface, and that she works or ferments still, which may be known by raking and plunging with the flat of the rake in the vat; being well raked, she is to remain still for one hour and a half more, carefully observing whether she casts blue. She is then to be served with water, and the quantity of indigo judged necessary is to be put in; it is commonly used in a liquid state, the full of a dyehouse kettle for each bale of woad; the vat being filled within six finger-breadths of her brim, is to be raked and covered as before; an hour after filling her with water, she must be served with lime, viz. two measures of lime for each bale of woad, giving more or less according to the quality of the woad, and what may be judged it will spend or take of lime.
I hope the reader will excuse my plainness; this Treatise being wrote for the Dyer, I must speak the language he is used to; the Philosopher will easily substitute proper terms, which perhaps the workman would not understand. There are kinds of woad readier prepared than others, so that general and precise rules cannot be given on this head. It must also be remarked, that the lime is not to be put into the vat till she has been well raked.
The vat being again covered, three hours after a pattern must be put in, and kept entirely covered fro an hour; it is then taken out to judge if she be fit to work. If she is, the pattern must come out green, and on being exposed a minute to the air, acquire a blue colour. If the vat gives a good green to the pattern, she must be raked, served with one or two measures of lime, and covered.
Three hours after, she must be raked, and served with what lime may be judged necessary; she is then to be covered, and one hour and a half after, the vat being pitched or settled, a pattern is put in, which must remain an hour to see the effects of the woad. If the pattern is of a fine green, and that it turns to a deep blue in the air, another must be dipt in to be certain of the effect of the vat. If this pattern is deep enough in colour, let the vat be filled up with hot water, or if at hand, with the old liquor of madder, and rake her well. Should the vat still want lime, serve her with such a quantity as you may judge sufficient by the smell and handling. This done, she must be again covered, and one hour after put in your stuffs, and make your overture. This is the term used for the first working of wool or stuffs in a new vat.
Marks by which you may know how to conduct a Vat regularly.
A vat is fit to work when the grounds are of a green brown, which changes, on its being taken out of the vat, when the flurry is of a fine Turkish or deep blue, and when the pattern, which has been dipt in it for an hour, comes out of a fine deep grass green. When she is fit to work, the bever has a good appearance, clear and reddish, and the drops and edges that are formed under the rake in lifting the bever are brown. Examining the appearance of the bever, is lifting up the liquor with the hand or rake, to see what colour the liquor of the vat has under its surface. the sediment or grounds must change colour (as has been already observed) at being taken out of the bever, and must grow brown by being exposed to the external air. The bever or liquor must feel neither too rough nor too greasy, and must not smell either of lime or lee. These are the distinguishing marks of a vat that is fit to work.
How to know when a Vat is cracked by too great or too small a Quantity of Lime; Extremes which must be avoided.
When more lime has been put in than was sufficient for the woad, it is easily perceived by dipping in a pattern, which, instead of turning to a beautiful grass green, is only daubed with a steely green. The grounds do not change, the vat gives scarcely any flurry, and the bever has a strong odor of quick lime, or its lees.
This error is rectified by thinning the vat, in which the Dyers differ; some use tartar, others bran, of which they throw a bushel into the vat, more or less in proportion to the quantity of lime used, others a pail of urine. In some places a large iron chafing-dish is made use of, long enough to reach from the ground to the top of the vat, this chafing-dish or furnace has a grate at a foot distance from its bottom, and a funnel coming from under this grate, and ascending to the top of the chafing-dish, which is to give air to, and kindle the coals which are placed on the grate. This furnace is sunk in the vat, near to the surface of the grounds, so as not to touch them, and is fastened with iron bars to prevent its rising. By this method the lime is raised to the surface of the liquor, which gives an opportunity to take off with a sieve what is thought superfluous; but when this is taken out, the necessary quantity of ware must be carefully restored to the vat. Others again thin the vat with pearl ashes, or tartar boiled in stale urine; but the best cure, when she is too hard, is, to put in bran and madder at discretion; and if she be but a little too hard, it will suffice to let her remain quiet four, five, or six hours, or more, putting in only two hats full of bran and three or four pounds of madder, which are to be lightly strewed on the vat, after which it is to be covered. Four or five hours after, she is to be raked and plunged, and according to the colour, that the flurry which arises from this motion, assumes and imprints on the whole liquor, a fresh proof is made by putting in a pattern.
If she is cracked, and casts blue only when she is cold, she must be left undisturbed, sometimes whole days without raking; when she begins to strike a tolerable pattern, her liquor must be reheated or warmed, then commonly, the lime, which seemed to have lost all power to excite a fermentation, acquires new strength, and prevents the vat from yielding its dye so soon. If she is to be hastened, some bran and madder are to be thrown on, as also one or two baskets of new woad, which helps the liquor that has been reheated to spend its lime.
Care must be taken to put patterns in each hour, in order to judge, by the green colour which they acquire, how the lime is worked on. By these trials she may be conducted with more exactness, for when once a vat is cracked, by too great or too small a quantity of lime, she is brought to bear with much more difficulty. If while you are endeavouring to bring her to work, the bever grows a little too cold, it must be heated by taking off some of the clear, and instead thereof, adding some warm water; for when the bever is cold, the woad spends little or no lime; when it is too hot, it retards the action of the woad, and prevents it from spending the lime; therefore it is better to wait a little, then to hasten the vats to come to work when they are cracked.
A vat is known not to have been sufficiently served with lime, and that she is cracked, when the bever gives no flurry, but instead thereof gives only a scum, and when she is plunged or raked, she only works, ferments and hisses, (this noise is made by a great number of air bubbles that burst as soon as they form) the liquor has also the smell of a common sewer or sink, or rotton eggs; it is harsh and dry to the touch; the grounds when taken out do not change, which generally happens when a vat is cracked for want of lime. This accident is chiefly to be apprehended when a vat is opened and a dip made in her; for if her state has not been looked into, both in regard to the smell as well as raking and plunging, and that the stuffs be imprudently put in when the woad has spent its lime, it is to be feared the vat may be lost; for the stuff being put in, the small quantity of lime that still remains in a state to act, sticks to them, the bever is divested of it, and the stuffs only blotted; these must be immediately taken out, and a quick remedy applied to the vat, to preserve the remaining part of the dye, which is done by putting in three or four measures of lime, more or less, according as the vat is cracked, and that without raking her bottom.
It is also to be observed, that if in raking and plunging the fermentation ceases, and the bad smell change, it is then to be supposed that the bever or liquor alone has suffered, and that the grounds are not yet in want. When the fermentation is in part or totally abated, and the bever has a smell of lime, and feels soft to the touch, the vat is to be covered and left at rest; and if the flurry still remains on the vat an hour and a half, a pattern is to be put in, which must be taken out one hour after, and you are to be guided according to the green ground it will take. But generally vats that are thus cracked, are not so soon brought to a state fit for dying.
The Opening of the Vat
The vat being come to work, the cross must be let down, and about thirty ells of cloth, or the equivalent of its weight of wool well scoured, (which is first intended to be dyed of a Persian blue to make a black afterwards) having returned this stirring several times, which must have always been covered with the liquor, the cloth must be twisted on the rings fastened to the jack at the top of the vat; if it be wool, it is to be dipt with a net, which will serve to wring it: the cloth must be opened by its lists to air it, and to cool the green, that is, to make it lose the green colour it had coming out of the vat, and take the blue. If this cloth or wool was not deep enough for a mazarine blue by the first dipping, it must get another, by returning into the vat the end of the pieces of cloth which first came out; and according to the strength of the woad, you must give to this striking two or three returns, as may be thought necessary for the intensity of the blue required. If the woad be good, such as the true L'Auragais is commonly, after taking out the first stirring, a second may be put in at this first opening of the vat. After making this opening, which is also called the first raking, the vat is to be again raked, and served with lime at discretion, observing that it has the smell and touch conformable to what has been laid down before, and taking notice, that in proportion as the dye diminishes, so does the strength of the woad.
If the vat be in good order at the first opening, three or four stirrings may be made, and the next day, two or three more; only observing not to hurry her, or to work her as strong as at first. That the vat may turn to as much profit as possible for the shades of blue; first, all stuffs intended to be black, are dyed; then the king's blue; after these the green brown; the violets and Turkish blues are commonly done in the last rakings of the second day of the opening. The third day, if the vat appears much diminished, she must be filled with hot water within four inches of the brim. This is called filling the vat.
The latter end of the week, the light blues are made, and on Saturday night, having raked the vat, she is to be served a little more than the preceding day, that she may keep till Monday.
Monday morning the bever is put on the fire, by passing it from the vat into the copper by a trough, which rests on both; this clear bever is emptied to the grounds, and when it is ready to boil it must be returned into the vat, raking the grounds, as the hot liquor falls from the trough; at the same time may be added a kettleful of prepared indigo.
When the vat is filled within four inches of the brim, and well raked, she must be covered, and two hours after a pattern put in, which must remain not more than an hour; lime must be added according to the shade of the green, which this proof pattern shall have taken, and at the expiration of an hour or two, if the vat has not suffered, the stuff is to be put in; having conducted it between two waters for about half an hour, it is wrung, and a dip is again given to it, as was done in the new vat. This vat heated again, is conducted in the same manner, that is, three rakings are made the first day, observing at each raking, whether she wants lime; for in this case, the quantity judged necessary must be given.
Blue made of woad alone, according to the opinion of some persons prejudiced in the favour of old customs, is much better than that which the woad gives with the addition of indigo. But then this blue would be much dearer, because woad gives much less dye than indigo, and it has been found by repeated experience, that four pounds of fine indigo from Guatimala, produced as much as a bale of Albigeois woad or pastel; and five pounds as much as a bale from L'Auragais, which generally weighs two hundred and ten pounds. So the using of the indigo with the woad is a great saving, as one vat with indigo shall dye as much as three without it.
Indigo is generally put into new vats after the woad yields its blue, and a quarter or half after she is to be served with lime; as this solution of indigo is already impregnated with some of its dissolution, the lime must be given with a more sparing hand than when the woad is used alone. At the re-heating, the indigo is put in on Saturday night, that it may incorporate with the bever, and that it may serve as garnish by its lime. The indigo that is brought from Guatimala in America is the best; it is brought over in the shape of small stones, and of a deep blue; it must be of a deep violet colour within, and when rubbed on the nail, have a coppery hue; the lightest is the best. It is necessary to observe, that for the better conducting of a woad vat, and to prevent accidents, a manufacturer ought to have a good woadman, this is the name given to the Journeyman Dyer, whose principal business is to conduct the woad, practice has taught him more than this treatise can furnish.
I shall make some reflections necessary to attain a more perfect knowledge of this process. The woad vat must never be re-heated but when fit for working; that is, she must have neither too much nor too little lime, but be in such a state as only to want heating to come to work. It is known she has too much lime (as has been before observed) by the quick smell; on the contrary, a want is known by the sweetish smell, and by the scum which rises on the surface by raking, being of a pale blue.
Care must be taken when a vat is intended to be re-heated, not to server her with lime in the evening, (unless in great want of it) for if she was too much served with it, she might next day be too hard, as the Dyers term it; for by heating her again, a greater action is given to the lime, and makes her spend it the quicker. Fresh indigo is commonly put into the vat, each time she is re-heated, in proportion to the quantity to be dyed. It would be needless to put i any, if there was but little work to do, or only light colours wanted. It was not permitted by the ancient regulations of France, to put more than six pounds of indigo to each bale of woad, because the colour of the indigo was thought not lasting, and that it was only the great quantity of woad which could secure and render it good; but it is now ascertained, both by the experiments of Monsieur Dufay, and those which I have since made, that the colour of Indigo, even used alone, is full as good, and resists as much the action of the air, sun and rain, as that of pastel or woad.
When a vat has been heated two or three times, and a good part has been worked off, the same liquor is often preserved, but part of the grounds are taken out, which is replaced by new woad; (this is called vamping); the quantity cannot be prescribed on this occasion, for it depends upon the work the Dyer has to do. Practice will teach all that can be wished for on this head. There are Dyers who preserve liquor in their vats several years, renewing them with woad and indigo in proportion as they work them; others empty the vat entirely, and change the liquor when the vat has been heated six or seven times, and that she gives no more dye. A series of practice alone will show which of these is preferable. It is however more reasonable to think, that by renewing it now and then, more lively and beautiful colours may be obtained, and the best Dyers follow this method.
In Holland they have vats which do not require to be so often heated. Mr. Van Robbais had some of these made some years since for their royal manufactory at Abbeville. The upper parts of these vats, to the height of three feet, are of copper, and the rest lead; they are also surrounded with a small brick wall, at seven or eight inches from the copper; in this interval embers are put, which keep up the heat of the vat a long time, so that she remains several days together in a condition to be worked, without the trouble of heating her over again. These vats are much more costly than the others, but they are very convenient, especially for the dipping of very light colours; because the vat is always fit to work, though she be very weak; this is not the case of the others, which generally make the colour a great deal deeper than required, unless they are set to cool considerably, and then it happens that the colour is not so good, nor has it the same brightness. To make these light colours in common vats, it is better to work some purposely that are strong with woad and weak of indigo; such give their colours flower, and light colours are made with greater ease.
As to the vats made after the Dutch fashion, and which have already been mentioned, the four which Mr. Van Robbais had in his manufactory, are six feet in depth, of which three feet and a half in the upper part are copper, and the two feet and a half of the bottom are lead. The diameter at the bottom is four feet and a half, and that at the top five feet four inches.
To return to the observations on heating the common vats. If the vat was heated when cracked, that is, when she has not quite lime enough, she would turn in the heating without being perceived, and perchance be entirely lost, as the heat would soon finish the spending of the lime, which was in too small a quantity. If this is perceived in time, it must be helped by pouring it back into the vat without more heating; then feed her with lime, and not heat her till she is come to work.
On the re-heating, some of the grounds must be put into the copper with the liquor or bever; and great care must be taken not to boil it, because the volatile necessary in this operation would evaporate. There are some Dyers, who, in heating their vats, do not put in the indigo immediately after the liquor is poured from the copper into the vat, but wait some hours till they see her come to work: this they do as a precaution, lest the vat should fail, and the indigo be lost; but by this method, the indigo does not so freely yield its colour, as they are obliged to work her as soon as she is fit, that she may not cool, so that the indigo, not being entirely dissolved, nor altogether incorporated, has no effect. It is therefore better to put it into the vat at the same time the liquor is cast in, and rake her well after. If the vat is heated over again without coming to work, she must not be scummed as in the common heatings, as the indigo would be carried off thereby, whereas, when she has worked, the scum is formed of the earthy part of the indigo and woad, united with a portion of lime.
When too much lime is put into a vat, you must wait for her till such time as she has spent it, or it may be accelerated by heating it, or by putting in ingredients which destroy in part the action of the lime, such as tartar, vinegar, honey, bran, some mineral acid, or any manner that will become sour; but all these correctors wear out the dye of the indigo and woad, so that the best method is, to let it spend of its own accord.
A vat is not commonly fed with lime, but on the first, second, and sometimes the third day, and it is also remarked, not to dip the violets, purples, or any other wool or stuffs which have previously a colour that may be easily damaged; the succeeding day after its being fed with lime, as it is then too active, it dulls the first colour; the fifth or sixth day the crimson may be dipt to give them a violet, and the yellows for green; following this rule, the colours will always be bright.
When a vat has been re-heated, she must come to work before she is served with lime; if this was done a little too soon, she would be cracked; the same thing would happen if some of the grounds were put into the copper. The most effectual method in this case is to let her rest before she is worked, until she comes to, which often happens in two, three or four hours, and sometimes a day.
By using light or weak lime, she grows too hard because this light lime remains in the liquor, and does not incorporate with the grounds. This is known by the strong smell of the liquor, and on the contrary the grounds have a sweetish smell, whereas the smell ought to be equal in both. The best way then is, to let it spend itself, by raking her often, in order to mix the lime with the grounds, until the smell of the vat is restored, and the flurry becomes blue.
A woad vat may be set without the addition of indigo, but then she yields but little colour, and only dyes a small quantity of wool or stuffs; for one pound of indigo, as has already been observed, affords as much dye as fifteen or sixteen pounds of woad. I set one of this kind to try the qualities of woad by itself, and I could not find that indigo was any way inferior to it, either for the beauty or solidity of the colour. As lime is always used, and sometimes sour liquors, in the setting of a vat, this is the proper place to speak of their preparation.
Preparation of Lime.
That the lime may be properly slacked for the Dyer's use, several pieces are immersed in water, one after another, and when each has remained till it begins to crackle, they are taken out to put in others, and after this manner they are cast into an empty vessel, where the lime finishes slacking, and reduces itself to powder, considerably augmenting its bulk; it is afterwards sifted through a canvas, and kept in a dry hogshead.
Sour liquors are not only necessary in some circumstances of setting a woad vat, but also in some of the preparations given to wool and stuffs previous to their being dyed; they are prepared after the following manner.
Preparation of sour Liquors.
A copper of the size required is filled with river water, and when it boils, it is flung into a hogshead, where a sufficient quantity of bran has been put, and stirred with a stick three or four times a day. The proportion of bran and water is not very material; I have made a good liquor by putting three bushels of bran into a vessel containing two hundred and fourscore quarts. Four or five days after, this water becomes sour, and consequently fit for use in most cases, where it will not be detrimental to the preparations of wool that are independent of dying.
For it may happen, that wool in the fleece which has been dyed in a liquor where too great a quantity of sour water has been put, will be harder to spin, as the sediment of the bran forms a soft of starch that glues the fibres of the wool, and prevents their forming an even thread. I must hear take notice of the bad custom of letting sour liquors remain in copper-vessels, as I have seen in some eminent dye houses; for this liquor being an acid, corrodes the copper, and if it remains long enough to take a portion of this metal, it will cause a defect both in the dye and in the quality of the stuff: in the dye, because the dissolved copper gives a greenish cast; in the quality of the stuff, because the copper dissolved preys on all animal substances. The Dyers are often ignorant of the cause of these defects.
I flatter myself to have omitted no essential point on the woad vat: If any difficulties or accidents, which I have mentioned, are not found in the practice they are not considerable, and an easy remedy will be found by those who make themselves familiar with the working part.
The readers who have no idea of this work, may think me too prolix, and find repetitions; but those who intend to make use of what I have taught in this chapter, will perhaps reproach me for not having said enough on the subject.
Those that read this chapter with attention, will not be surprized that the master-piece for apprentices to Dyers of the great dye, is, to set the woad vat and work her.
I placed in a copper a small vessel containing fifty quarts, and filled two-thirds with a liquor made of river water, one ounce of madder, and a little weld, putting in at the same time a good handful of wheaten bran and five pounds of woad. The vat was well raked and covered; it was then five in the evening; it was again raked at seven, nine, twelve, two, and four o'clock; the woad was then working, that is, that vat was slowly coming to work, as I have already related of that of the pastel.
Pretty large air bubbles formed themselves, but in a small quantity, and had scarcely any colour. She was then served with two ounces of lime and raked. At five o'clock a pattern was put in; which was taken out at six, raking her; this pattern began to have some colour; another was put in at seven, at eight she was raked, and the pattern came out pretty bright; an ounce of indigo was then put in; at nine another pattern, at ten she was raked, and an ounce of lime was added, because she began to have a sweetish smell; at eleven a pattern, at twelve she was raked; it was thus continued till five, then three ounces of indigo were put in, at six a pattern, at seven she was raked. It would then have been proper to have served her with water, as she was at that time perfectly come to work, the pattern that was taken out being very green, and turning of a bright blue. But besides that I was fatigued, having sat up the whole night, I chose rather to put her back to the next day, to see her effect by day-light; and for that purpose, I put one ounce of lime, which kept her up till nine in the morning; from time to time patterns were put in, the last that was taken out was very beautiful; she was served with a liquor composed of water, and a small handful of bran. She was raked, and patterns put in from hour to hour; at five she was come to work; she was afterwards served with lime, and raked to preserve her till she was to be re-heated.
Some time after I set another with the woad alone, without indigo, that I might be able to judge of the lasting of the dye of the woad, which, upon trial, I found to be as good as the pastel or garden woad. Thus all superiority the pastel has on the woad, is, that the latter yields less dye than the former.
The little varieties that may be observed in setting these different vats at work, prove, that there are many circumstances in these processes that are not absolutely necessary. It appears to me, that the only important point, and that to which the greatest attention is to be given, is, in the conducting the fermentation with care, and not to server her with lime, but when judged necessary by the indications I have laid down. As to the indigo being put in at twice, or altogether, a little sooner than later, it appears very indifferent. The same may be said of the weld, which I made use of twice, and suppressed the two other times, and of pearl-ashes, which I added in a small quantity in the small pastel vat, and suppressed in the woad vat. In short, I believe, and it appears to me to a demonstration, that the greatest regard is to be had to the proper distribution of the lime, throughout the whole course of the working of the vats, either to set them at work, or to re-heat them. I must also add, that when a woad vat is set to work, it cannot be too often inspected into to know her state; for if there are some that are backward (which is attributed to the weakness of the woad) there are also others that very quickly come to work. I have seen a middling one of seventy pounds of woad, poisoned; because the woad man neglected to inspect her as often as she required, and she had been two hours fit to work before he discovered it; the grounds were entirely come up to the surface of the liquor, and the whole had a very sour smell; it was not possible to bring her back, and they were obliged to fling her away, as she would in a short time have contracted a foetid smell. The retarding of the action of the vat may also proceed from the temperature of the air; for the vat cools a great deal sooner in winter than in summer; therefore it becomes necessary to watch it attentively, though commonly they are fourteen or fifteen hours before they come to work.
I shall endeavour to explain, in the sequel, how the colouring part of this ingredient, so necessary in dying, displays itself; but I must first of all speak of vats which are prepared from indigo.
In this state, the cocks of the steeper are turned, and all the water let out stained with the colouring parts of the plant into the second, called the beater; because this water is beat by a mill or machine that has long sticks, to condense the substance of the indigo, and precipitate it to the bottom. By this means the water becomes clear and colourless, like common water; then the cocks are turned, that the water may run off from the surface of the blue sediment; after which, other cocks are turned that are at the bottom, that all the secula may fall into the third vat, called the reposer; for it is there the indigo remains to dry; it is then taken out to be made into cakes, &c. See, on this subject, Histoire des Antilles, pare le Pere Labot.
At Pondicherry, on the coast of Coromandel, there are two kinds of indigo, the one a great deal finer than the other; the best is seldom used but to lustre their silks, the inferior in dying. They augment in price according to their quality; there is some which cost from 15 pagodas the bar (which weighs 48 pounds) to 200 pagodas. The most beautiful is prepared nigh Agra. There is also a very good kind that comes from Masalupatan and Ayanon, where the East India Company have a factory. At Chandernagor it is called nill when it is prepared and cut to pieces. The indigo of Java is the best of all; it is also the dearest, and consequently few Dyers use it. Good indigo ought to be so light as to float on the water; the more it sinks, the more it may be suspected of being adulterated by a mixture of earth, cinders, or pounded slates. It must be of a deep blue, bordering on the violet, brilliant, lively and shining; it must be finer within, and appear of a shining hue. Its goodness is tried by dissolving it in a glass of water; if it be unmixed and well prepared, it will dissolve entirely; if sophisticated, the foreign matter will sink to the bottom. Another method of trying it is by burning; good indigo burns entirely away, and when adulterated, the mixture remains after the indigo is consumed.
Powdered indigo is much more subject to adulteration than that which is in cakes: for it is a difficult matter that sand, powdered slates, &c. should unite so as not to form together in different places layers of different matters; and, in this case, by breaking the lump indigo, it is easily discovered.
Method of working the Indigo Vat.
There are several methods of preparing the indigo vat; I tried all those I knew, and they all succeeded. I shall describe them after the most exact manner, beginning with that which is the most in use, and almost the only one known at Paris.
It is a vat which is about five feed in height, two feet diameter, and becomes narrow towards the bottom; she is surrounded with a wall that leaves a space round her, which serves to hold embers. In a vat of this size, two pounds of indigo may at least be used, and five or six for the greatest proportion. To set a vat of two pounds of indigo in such a vessel that may contain about fourscore quarts, about sixty quarts of river water are set to boil in a copper for the space of half an hour, with two pounds of pearl ashes, two ounces of madder, and a handful of bran; during this, the indigo is prepared after the following manner:
Two pounds of it are weighed out, and cast into a pail of cold water to separate the earthy parts. The water is afterwards poured off by inclination, and the indigo well ground; a little warm water is put into it, shaking it from side to side; it is poured by inclination into another vessel; what remains is still ground, and fresh water put in to carry off the finest parts, and thus continued till all the indigo is reduced into a powder, fine enough to be raised by the water. This is all the preparation it undergoes. Then the liquor which has boiled in the copper with the grounds are poured into the high and narrow vat, as likewise the indigo; the whole is then raked with a small rake, the vat is covered, and embers placed round her.
If this work was begun in the afternoon, a few embers are added at night; the same is repeated the next day morning and night. The vat is also lightly raked twice the second day; the third day, the embers are continued to be put round, to keep up the heat of the vat; she is raked twice in the day: about this time, a shining copper-coloured skin begins to appear on the surface of the liquor, and appears as if it was broken or cracked in several places. The fourth day, by continuing the fire, this skin or pelicle is more formed and closer; the flurry, which rises in raking the vat, appears, and the liquor becomes of a deep green.
When the liquor is in this state, it is a sign that it is time to fill the vat. For this purpose a fresh liquor is made, by putting into a copper about twenty quarts of water, with one pound of pearl ashes, a handful of bran, and half an ounce of madder. This is boiled a quarter of an hour, and the vat is served with it; she is then raked, and causes a great quantity of flurry to rise, and the vat comes to work the next day; this is known by the quantity of flurry with which she is covered by the skin or copper-scaly crust which swims on the liquor, which, although it appears of a blue-brown, is nevertheless green underneath.
This vat was much longer coming to its colour than the others, because the fire was too strong the second day, otherwise she would have been fit to work two days sooner. This did no damage but retarded her, and the day she came to work, we dipt in serges weighing thirteen or fourteen pounds. As this caused her to lose her strength, and the liquor being diminished by the pieces of stuff that had been dyed in her, she was served in the afternoon with fresh liquor, made with one pound of pearl ashes, half an hounce of madder, and a handful of bran; the whole was boiled in a copper for a quarter of an hour; the vat being served with it she was raked, covered, and a few embers put round. She may be preserved after this manner several days, and when she is wanted to work, she must be raked over night, and a little fire placed about her.
When there is occasion to re-heat, and add indigo to this kind of vat, two thirds of the liquor (which then is no more green, but of a blue-brown and almost black) is put into a copper; when it is ready to boil, all the scum that is formed at the top is taken off with a sieve; it is afterwards made to boil, and two handfuls of bran, a quarter of a pound of madder, and two pounds of pearl ashes are added. The fire is then removed from the copper, and a little cold water cast into it to stop the boil; after which the whole is put into the vat, with one pound of powdered indigo, diluted in a portion of the liquor as before related; after this the vat is raked, covered, and some fire put round; the next day she is fit to work.
When the indigo vat has been reheated several times, it is necessary to empty her entirely, and to set a fresh one, or she will not give a lively dye; when she is too old and stale, the liquor is not of so fine a green as at first.
I put several other vats to work after the same method, with different quantities of indigo, from one pound to six; always observing to augment or diminish the other ingredients in proportion, but always one pound of pearl ashes to each pound of indigo. I have since made other experiments, which proved to me that this proportion was not absolutely necessary; and I make no doubt but that several other means might be found to make the indigo come to as perfect a colour. I shall, nevertheless, proceed to some other observations on this vat.
Of all these I set to work, after the manner described, only one failed me, and that by neglecting to put fire round her the second day. She never came to a proper colour; powdered arsnic was put in to no effect, red hot bricks were also plunged in at different times; the liquor turned of a greenish hue, but never came to the proper colour; and having attempted several other means without success, or without being able to find out the cause of her not succeeding, I caused the liquor to be emptied and cast away.
All the other accidents that have happened me in conducting the indigo vat, have only lengthened the operation; so that this process may be looked upon as very easy when compared to that of the woad vat. I have also made several experiements on both, in which my chief view was to shorten the time of the common preparation; but not meeting with the desired success, I shall not relate them.
The liquor of the indigo vat is not exactly like that of the woad; its surface is of a blue-brown, covered with coppery scales, and the under part of a beautiful green. The stuff or wool dyed in this is green when taken out, and becomes blue a moment after. We have already seen that the same happens to the stuff dyed in the woad vat, but it is remarkable, that the liquor of the last is not green, and yet produces on the wool the same effect as the other. It must also be observed, that if the liquor of the indigo vat be removed out of the vessel in which it was contained, and if too long exposed to the air, it loses its green and all its quality, so that, although it gives a blue colour, that colour is not lasting.
I shall examine this more particularly in the sequel, and endeavour to give the chymical theory of this change.
This vat may at pleasure be made more or less considerable by augmenting or diminishing the ingredients in proportion to the indigo intended to be made use of; so that to each pound of indigo add a quart of vinegar, two ounces of madder, and sixty or seventy quarts of urine. This vat comes sooner to work in summer than in winter, and may be brought sooner to work by warming some of the liquor without boiling, and returning it into the vat; this process is so simple that it is almost impossible to fail.
When the indigo is quite spent, and gives no more dye, the vat may be charged again without setting a new one. For this purpose, indigo must be dissolved in vinegar, adding madder in proportion to the indigo, pouring the whole into the vat, and raking her night, and morning, and evening as at first, she will be as good as before; however she must not be charged this way above four or five times, for the ground of the madder and indigo would dull the liquor, and in consequence render the colour less bright. I did not try this method, and therefore do not answer for the success; but here follows another with urine which gives a very lasting blue, and which I prepared.
Hot Vat with Urine.
A pound of indigo was steeped twenty-four hours in four quarts of clear urine, and when the urine became very blue, it was run through a fine sieve into a pail, and the indigo which could not pass, and which remained in the sieve, was put with four quarts of fresh urine; this was so continued till all the indigo had passed through the sieve with the urine; this lasted about two hours. At four in the afternoon three hogsheads of urine were put into the copper, and it was made s hot as could be without boiling. The urine cast up a thick scum, which was taken up with a broom and cast out of the copper. It was thus scummed at different times, till there only remained a white and light scum; the urine, by this means sufficiently purified and ready to boil, was poured into a wooden vat, and the indigo prepared as above, put in; the vat was then raked, the better to mix the indigo with the urine; soon after, a liquor was put into the vat, made of two quarts of urine, a pound of roach-alum, and a pound of red tartar.
To make this liquor, the alum and tartar were first put into the mortar, and reduced to a fine powder, upon which two quarts of urine were poured, and the whole rubbed together, till this mixture, which rose all of a sudden, ceased to ferment: it was then put into the vat, which was strongly raked; and being covered with its wooden cover, she was left in that state all night; the next morning the liquor was of a very green colour; this was a sign she was come to work, and that she might have been worked if thought proper, but nothing was dyed in her; for all that was done, was only, properly speaking, the first preparation of the vat, and the indigo which had been put in was only intended to feed the urine, so that to finish the preparation the vat was let to rest for two days, always covered, that she might cool the flower; then a second pound of indigo was prepared, ground with purified urine as before. About four in the afternoon all the liquor of the vat was put into the copper; it was heated as much as possible without boiling; some thick scum formed on it which was taken off, and the liquor being ready to boil was returned into the vat. At the same time the ground indigo was put in, with a liquor made as above of one pound of alum, one pound of tartar, and two quarts of urine, a fresh pound of madder was also added; then the vat was raked, well covered, and left so the whole night. The next morning she was come to work, the liquor being very hot, and of a very fine green, she was worked with wool in the fleece, of which thirty pounds were put into the vat. It was well extended and worked between the hands, that the liquor might the more easily soak into it; then it was left at rest for an hour or two, according as lighter or deeper blues are required.
All this time the vat was well covered, that it might the better retain its heat, for the hotter she is, the better she dyes, and when cold acts no more. When the wool came to the shade of the blue required, it was taken out of the vat in parcels, about the bigness of a man's head, twisted and wrung over the liquor as they were taken out, till from green, as they were coming out of the vat, they became blue. This change from green to blue is made in three or four minutes. These thirty pounds being thus dyed, and the green taken off, the vat was raked, and suffered to rest for two hours, being all that time well covered; then thirty pounds more were put in, which was well extended with the hands, the vat was covered, and in four or five hours this wool was died at the height or shade of the first thirty pounds; it was then taken out in heaps, and the green taken off as before. This done, the vat had still some little heat, but not sufficient to dye fresh wool; for when she has not a sufficient heat, the colour she gives would neither be uniform nor lasting, so that it must be re-heated, and fresh indigo put in as before. This may be done as often as judged proper, for this vat does not spoil by age, provided, that whilst she is kept without working, a little air is let into her.
Re-heating of the Vat with Urine
About four in the afternoon, the whole liquor of the vat was put into a copper, and a sufficient quantity of urine added to this liquor, to make up the deficiency that had been lost by evaporation during the preceding work. This filling commonly takes eight or nine pails of urine; the liquor was then heated and scummed as before, and when ready to boil, returned into the vat with a pound of indigo, and the liquor above described, consisting of alum and tartar, of each one pound, madder one pound, and two quarts of urine. After raking the vat well, and covering her, she was left at rest the whole night.
The next day she came to work, and sixty pounds of wool were dyed in her at twice as before. It is after this manner all the re-heatings must be done the evening before the dying, and these re-heatings may extend to infinity, as the vat, once set, serves a long time.
I must here observe, that the greater the quantity of indigo put in at once is, the deeper the blue; thus, instead of one pound, four, five or six pounds may be put in together; nor is it necessary to augment the dose of alum, tartar, or madder, of which ingredients the liquor is composed; but if the vessel hold more than three hogsheads, then the dose of these must be augmented in proportion. The vat I have mentioned held three, and was too small to dye at one time a sufficient quantity of wool to make a piece of cloth, viz. fifty or sixty pounds; for this purpose it would be necessary that the vat should contain at least six hogsheads, and from this a double advantage would arise. 1. All the wool will be dyed in three or four hours, whereas dying it at twice, it takes eight or ten hours. 2. At the end of three hours, in which time the wool would be dyed, taken out, and the green taken off, the vat being yet very hot; after raking and letting her rest a couple of hours, the same wool might be returned into her, which would heighten the colour very much; for all wool that has been dyed, aired, and the green taken off, always takes a finer colour than new or white wool, which might remain twenty hours in the vat.
Great care must be taken to air and take off the green of the dyed parcels of wool that are taken out of the vat hastily, that the air may strike them equally, without which the blue colour will not be uniform throughout the wool.
There are manufacturers who say that cloths, whose wool has received this ground of blue with urine, cannot be perfectly scoured at the fulling mill, even at twice; others vouch the contrary, and I am of the opinion the last speak the truth; yet, if the first are right, it might be suspected that the animal oil of the urine becoming resinous by drying on the wool, or by uniting with the oil with which the wool is moistened; for its other preparations more strongly resist the fuller's earth and soap, than a simple oil by expression. To remedy this, the wool ought to be well washed in a running water after it is dyed, twisted, aired, the green taken off, and cooled. Be it as it may, the woad vat will always be preferred in the great dye-houses to these kinds of indigo vats made with urine or otherwise; and for this reason, that with a good woad vat, and an ingenious woadman, much more work is despatched than with all the other blue vats.
I have described the indigo vats in this treatise, not with a design to introduce them in the large manufactories, but to procure easy means to the Dyers in small, and small manufactories, to whom I wish this work may be of as much advantage as to the others. I shall therefore here describe a cold vat, which may be used with advantage by those who dye small stuffs, in whose composition thread and cotton enter. The colour is lasting, but cannot be made use of for wool.
Dissolve three pounds of indigo powdered finely, in a glazed earthen pot, with three pints of strong soap-boilers lees, which is a strong lee of soda and quick lime. The indigo takes about twenty-four hours dissolving, and when perfectly so, remains suspended in the liquor, thickens it, and gives it the consistence of an extract. At the same time, three pounds of sifted slacked lime must be put into another vessel, with six quarts of water, and boiled together for a quarter of an hour; when settled, the clear is poured off by inclination. Then three pounds of green copperas are to be dissolved in this clear lime water, and the whole let to rest till the next day. Three hundred quarts of water are then put in a large deal vessel (no other wood but deal will do, for it would dull and blacken the dye, especially if it was oak.) The two solutions which were made the day before are put in, the vat is well raked, and suffered to rest. I have seen her come to colour in two hours after, but this never fails to happen the next day at farthest. She makes a great deal of slurry, and the liquor becomes of a fine green colour, but a little more on the yellow than the green of the common vat.
When this vat begins to spend herself, she is to be quickened without putting in fresh indigo, by making a small liquor with two pounds of green copperas, dissolved in a sufficient quantity of lime water; but when the indigo has spent all its colour, she must be re-charged by putting in fresh, dissolved in such a lee as has been described.
Water of Old Iron.
Some Dyers put into this vat a little water of old iron. It is a mixture of vinegar and water, in which some old iron nails have been put to rust. They say this makes the colour more lasting, but I have experienced, that it is sufficiently so without this, and as good as the other blues, of which I have before given the preparation.
I set several vats; those that required to be heated were put in a bath or sand-heat, in small glass bodies; and those that are worked cold were left without doing any thing to them. These last are easy, being sufficient to diminish the quantity of liquor, and of all the other ingredients, in proportion to the vessel that is to be set, and it is almost impossible to fail.
As to that which I first described, which is set hot, it is somewhat more difficult, and that several might be willing to try the experiment, which in itself is curious, and neither requires experience nor apparatus to perform in small, I shall give the process of one which succeeded perfectly, and in which I had designedly put a greater quantity of indigo than usually is done in the common proportion.
I boiled two quarts of water with two scruples of madder and four ounces of pearl-ashes; after boiling a quarter of an hour, I put it into a body, which held about four quarts, and had been previously heated with warm water, and in which I had put a quarter of a handful of bran. The whole was well stirred with a deal spatula, the glass body put on a very gentle sand-heat, which only kept it warm, and pretty near the same degree of heat that is required for the common indigo vat.
The fire was kept all night, and the next day under the sand-heat, without any sensible change happening; it was only stirred twice a day. The next day some flurry began to rise, and a copper coloured skin formed on the surface, and the liquor was of a green-brown; it was then filled up with a liquor made of a quart of water, two ounces of pearl ashes, and a little bran. I mixed the whole together, then let it rest. It came perfectly well to colour, and the next day I dyed several middling pieces of stuffs and wool. These small vessels may be reheated and charged again as easily as a large one.
I think I have nothing more to say concerning the method of setting to work all these kinds of blue vats; yet I am persuaded that there are several other means practised in different places, and that it is even easy to contrive new ones; however, I can affirm that all those which I have described are very sure, and that they have all been worked several times with the same success.
It is an ancient custom among Dyers to reckon thirteen shades of blue from the deepest to the lightest. Although their denominations be somewhat arbitrary, and that it is impossible exactly to fix the just passage from one to the other, I shall notwithstanding give the names. They are as follow, beginning with the lightest: milk-blue, pearl-blue, pale blue, flat-blue, middling-blue, sky blue, queen's blue, turkish-blue, watchet-blue, garter-blue, mazareen-blue, deep-blue and very deep blue. These distinctions are not equally received by all Dyers, nor in all provinces, but the most part are known; and it is the only method that can be taken to give the idea of the same colour, whose only difference is in being more or less deep.
It is easy to make deep blues. I have already said, that to effect this, the wool or stuffs are to be returned several times into the vat; but it is not so in respect to light blues; for when the vat is rightly come to work, the wool can seldom be left in short time enough, but that it takes more than the shade required. It often happens when a certain quantity of wool is to be dipped, and that it cannot all be put in at the same time, that what goes in at first is deeper than the other. There are some Dyers who, to obviate this inconveniency in making very light blues, which they call milk and water, take some of the liquor of the indigo vat, and dilute it in a very great quantity of lukewarm water; but this method is a bad one, for the wool dyed in this mixture has not near so lasting a colour as that dyed in the vat; as the altering ingredients which are put into the vat with the indigo, serves as much to dispose the pores of the subject which is dipped in, as to the opening of the colouring secula which is to dye it, their concourse being necessary for the adhesion of the colour. The best method of making these very light blues, is to pass them either in a woad or indigo vat, out of which the colour has been worked, and begins to cool. The woad vat is still preferable to that of the indigo, as it does not dye so soon.
The blues made in vats that have been worked are duller than the others; but they may be pretty sensibly roused by passing the wool or stuffs in boiling water. This practice is even necessary to the perfection of all blue shades; by this the colour is not only made brighter, but also rendered more secure, by taking off all that is not well incorporated with the wool; it also prevents its spotting the bands or linen, which commonly happens, and the Dyers, to gain time, neglect this precaution. After the wool is taken out of the warm water, it is necessary to wash it again in the river, or at least in a sufficient quantity of water for the carrying off all the superfluous loose dye.
The best method to render the blue dye brighter, is by filling them with a thin liquor of melted soap, and afterwards cleansing them from the soap by warm water, and, if convenient, by rinsing them in an old cochineal liquor. This method is to be taken with deep blues; but if the same was taken with very light blues, they would lose their bright blue lustre, and incline to grey.
I hope to have removed all difficulties on the preparation of blue, and in the method of dying it. Some Dyers, for the sake of gain, spare the woad and indigo, and use for blue, orchel or logwood, and brazil; this ought to be expressly forbid, though this adulterated blue is often brighter than a lasting and legitimate blue. I shall take notice of this in the chapters treating on the lesser dye.
I shall now explain the theory of the invisible change of the blue dye. This colour, which I shall here only consider in relation to its use in the dying of stuffs of what kind soever, has hitherto been extracted only from the vegetable world, and it does not appear that we can hope to use in this art the blues the painters employ; such are the Prussian blue, which holds of the animal and mineral kind*; the azure, which is a vitrified mineral substance; the ultramarine, which is prepared from a hard stone; the earths that have a blue colour, &c. These matters cannot, without losing their colour in whole or in part, be reduced into atoms sufficiently minute, so as to be suspended in the saline liquid, which must penetrate the fibres of the animal, and vegetable substances of which stuffs are manufactured; for under this name linen and cotton cloths must be comprehended, as well as those wove of silk and wool.
* 1748, Mons. Macquer, of the Royal Academy of Sciences, found the means of using the Prussian blue to dye silk and cloth in a blue whose brightness surpassed all the blues hitherto known.
Hitherto we know but of two plants that yield blue after their preparation: the one is the isatis or glaustum, which is called pastel in Languedoc, and woad in Normandy. Their preparation consists in a fermentation continued even to the putrefacation of all the parts of the plant, the root excepted; and consequently in the unfolding of all their principles into a new combination, and fresh order of these same principles, from whence follows an union of infinite fine particles, which applied to any subject whatever, reflects the light on them very different from what it would be, if these same particles were still joined to those which the fermentation has separated.
The other plant is the anil, which is cultivated, in the East and West Indies, out of which they prepare that secula that is sent to Europe under the name of indigo. In the preparation of this plant the Indians and Americans, more industrious than ourselves, have found out the art of separating only the colouring parts of the plant from the useless ones; and the French and Spanish colonies have imitated them, and thereby made a considerable increase of commerce.
That the indigo, such as is imported from America, should deposit on the wool or stuffs the colouring parts required by the Dyer, it is infused several ways, the processes of which we have already given. They may be reduced to three; the cold indigo vat may serve for thread and cotton; those that are made use of hot, are fit for stuffs of any kind whatever. In the cold vat, the indigo is mixed with pearl-ashes, copperas or green vitriol, lime, madder and bran. The hot vats are either prepared with water or urine; if with water, pearl-ashes and a little madder must be added; if with urine, alum and tartar must be joined to the indigo. Both of these vats, principally intended for wool, require a moderate degree of heat, but at the same time strong enough for the wool to take a lasting dye, I mean such as will withstand the destroying action of the air and sun, the proof of dyes.
I have prepared, as I said before, these three vats in small, in cylindrical glass vessels, exposed to the light, in order to see what passed before the infusion came to a colour, that is, whether it was green beneath the slurry at the surface, which is a sign of internal fermentation. I have said that the green colour of the liquor is a condition absolutely essential, and without which, the colour the stuff would take would not be a good dye, and would almost entirely disappear on the least proofs.
I shall now give a description of the cold indigo vat in small, for the changes are much better seen in her, and for this reason, that what happens in the two others is not very essentially different. It is proper to take notice, that which I shall call part, in this Observation of Experiements, is a measure of the weight of four drachms, of all matter either liquid or solid, and that it will be this quantity that must be supposed, each time that I use that word in the detail of these experiments.
I put three hundred parts of water into a vessel, containing five hundred and twelve, or eight quarts, in which I dissolved six parts of copperas, which gave the liquor a yellow dye. Six parts of potashes were also dissolved by themselves in thirty-six parts of water. The solution made, I digested in it six parts, or three ounces, of indigo of St. Domingo well ground; it was left over a very gently fire three hours. The indigo swelled, and taking up a larger space, rose from the bottom of this alkaline liquor, with which it formed a kind of thick syrup, which was blue. This was a proof that the indigo was only divided, but not dissolved, for had its solution been perfect, that thick liquor would have been green instead of blue; for all liquor that has been tinged blue by a vegetable of any kind, grows green on the admixion of an alkaline salt, either concrete or in a liquid form, whether it be a fixed or volatile.
From hence the reason is discovered why indigo does not dye a stuff of a lasting blue when its liquor is not green; for its solution not being complete, the alkali cannot act upon these first elementary particles; as for example, it acts on the tincture of violets, which is a perfect solution of the colouring parts of those flowers, which it turns green in an instant, and on the first contact.
I poured this thick blue liquor into the solution of vitriol, and after well shaking the mixture, I added six parts of lime that had been slacked in the air; it was cold weather when this experiment was made; the thermometer was at two degrees under the freezing point, which was the cause that this was near four days coming to a colour, and the fermentation, which must naturally ensue in all vitriolic liquor, where an alkaline salt has been put in, such as pot-ashes, and an alkaline earth, was carried on with so much slowness that very little scum appeared on the surface of the liquor. In a hot season, and by making use of lime newly calcined, these kind of vats are sometimes fit to dye in four hours.
Each time I stirred the mixture with a spatula, I observed that the iron of the vitriol or copperas was the first that precipitated to the bottom of the vessel, and that the alkaline salt had precipitated it, to join itself to the acid. Thus in this process of the cold indigo vat, a tartar of vitriol after the manner of tachemius is formed; whereas by the common method of preparing this neutral salt, the acid of the vitriol is poured on a true alkaline salt, such as salt of tartar or pot-ashes. This again is a circumstance that leads insensibly to the theory of good dye. I desire the reader to take notice of this, as it will occur in the sequel of this observation, as well as in other chapters.
The earthy parts of the lime precipitate next after the iron; they are easily distinguished by the whiteness, which are yet difficult to distinguish when the colouring parts of the indigo are sufficiently loosened. In short, under this white earth the secula of the indigo deposits itself, and by degrees rarifies in such a manner, that this substance, which the first day was only an eight of an inch above the precipitated lime, rose insensibly within half an inch of the surface of the liquor, and the third day grew so opaque and muddy, that nothing further could be distinguished.
This rarefaction of the indigo, slow in winter, quick in summer, and which may be accelerated in winter by heating the liquor to fifteen or sixteen degrees, is a proof that a real fermentation happens in the mixture, which opens the little lumps of indigo, and divides them into particles of an extreme fineness; then their surfaces being multiplied almost ad infinitum, they are so much the more equally distributed in the liquor, which deposits them equally on the subject dipped in to take the dye.
If fermentation comes on hastily, or in a few hours, whether on account of the heat of the air, or by the help of a small fire, a great quantity of slurry appears; it is blue, and its reflection they have also named coppery, because the colours of the rainbow appear in it, and the red and yellow here predominate; however this phenomenon is not peculiar to indigo, since the same reflection is perceived in all mixtures that are in actual fermentation, and particularly in those which contain fat particles blended with salts, urine, soot, and several other bodies put into fermentation, show on their surface the same variegated colours.
The flurry of the indigo vat appears blue, because exposed to the external air; but if a small portion of the liquor which is under it be taken up with a spoon, it appears more or less green in proportion as it is filled with colouring particles. In the course of this observation, I shall show the reason of this difference, or, at least, a probable explication of this change of blue, which, as I have said before, is absolutely necessary for succeeding in the process described.
When the vat is in this state, it has already been said that cotton, thread, cloths wove from them, &c. may be dyed in her, and the colours which they take are of the good dye; that is, this cotton and thread will maintain them, even after remaining a suitable time in a solution of white soap, actually boiling. This is the proof given them preferable to any other, because the linen and cotton cloths must be washed with soap when dirty.
Though the indigo liquor which is in this state can make a lasting dye without the addition of any other ingredient; the Dyers who use this cold vat add, as in the other hot vats, a decoction of madder and bran in common water run through a sieve; this is what they call bever. They put madder to insure, as they say, the colour of the indigo, because this root affords a colour so adhesive that it stands all proofs; they put the bran to soften the water, which they imagine generally to contain some portion of an acid salt, which according to their opinion, must be deadened.
This was the opinion of the French Dyers against indigo in the days of Monsieur Colbert; and as this minister could not spare time to see the experiments performed in his presence, on the foundation of this report, he forbad indigo to be used alone. But since the Government has been convinced, by new experiments made by the late Mr. Dufay, that the stability of the blue dye of this ingredient was such as could be desired; the new regulation of 1737 licenses the Dyers to use it alone, or mixed with woad; so that if they continue to use the madder, it is rather because this roote giving a pretty deep red, and this red mixing with the blue of the indigo, gives it a tint which approaches the violet, and also a fine hue.
As to the bran, its use is not to deaden the pretended acid salts, but to disperse throughout a quantity of sizey matter; for the small portion of flour which remains in it, dividing itself into the liquor, must diminish in some measure its fluidity, and consequently prevent the colouring particles which are suspended in it, being precipiated too quick, in a liquor which ad not acquired a certain degree of thickness.
Notwithstanding this distributed throughout the liquor, as well from the bran as the madder, which also affords something glutinous, the colouring particles will subside if the liquor remains some days without being stirred; then the top of the liquor gives but a feeble tint to the body dipped in, and if a strong one is wanted, the mixture must be raked, and left to rest an hour or two, that the iron in the copperas, and the gross parts of the lime may fall to the bottom, which otherwise would mix with the true colouring particles, and prejudice their dye, by depositing on the body to be dyed a substance that would have but little adhesion, which in drying would become friable, and of which each minute part would occupy a space, where the true colouring particle could neither introduce nor deposit itself by an immediate contact on the subject.
Not to deviate from the method followed by the Dyers, I boiled one part of grape-madder and one of bran, in 174 parts of water: this proportion of water is not necessary, more or less may be put, but I wanted to fill my vessel, which contained 512 parts. I passed this bever through a cloth and squeezed it, putting this liquor, still hot, and which was of a blood-red, into the indigo liquor, observing the necessary precautions to prevent the breaking of the glass vessel. The whole was well stirred, and two hours after the liquor was green, and consequently fit for dying. It dyed cotton of a lasting blue, somewhat brighter than it was before the addition of the red of madder.
I shall now endeavour to find out the particular cause of the solidity of this colour; perhaps it may be the general cause of the tenacity of all the rest; for it appears already, from the experiments above related, that this tenacity depends on the choice of salts, which are added to the decoctions of the colouring ingredients, when the same ingredients contain none in themselves. If from the consequences which shall result from the choice of these salts, of their nature, and of their properties, it be admitted (and it cannot be fairly denied) that they afford more or less tenuity in the homogeneous colouring parts of the dying ingredients, the whole theory of this art will be discovered, without having recourse to uncertain or contested causes.
One may easily conceive that the salts added to the indigo vats not only open the natural pores of the subject to be dyed, but also unfold the colouring atoms of the indigo.
In the other preparations of dyes (to be mentioned hereafter) the woolen stuffs are boiled in a solution of salts, which the Dyers call preparation. In this preparation tartar and alum are generally used. In some hours the stuff is taken out, slightly squeezed, and kept damp for some days in a cool place, that the saline liquor which remains in it may still act, and prepare it for the reception of the dye of these ingredients, in the decoction of which it is plunged to boil again. Without this preparation, experience shows that the colours will not be lasting, at least for the greatest part; for it must be owned that there are some ingredients which yield lasting colours, though the stuff has not previously undergone this preparation, because the ingredient contains in itself these salts.
It is therefore necessary, that the natural pores of the fibres of the wool should be enlarged and cleansed by the help of those salts, which are always somewhat corroding, and perhaps they open new pores for the reception of the colouring atoms contained in the ingredients. The boiling of this liquor drives in the atoms by repeated strokes. The pores already enlarged by these salts, are further dilated by the heat of the boiling water; they are afterwards contracted by the external cold when the dyed matter is taken out of the copper, when it is exposed to the external air, or when it is plunged into cold water. Thus the colouring atom is taken in, and detained in the pores or fissures of the dyed body, by the springiness of its fibres, which have contracted and restored themselves to their first state, and have re-assumed their primary stiffness upon being exposed to the cold.
If, besides this spring of the sides of the pore, it be supposed that these sides have been plaistered inwardly with a layer of the saline liquor, it will appear plainly that this is another means employed by art to detain the colouring atom; for this atom, having entered into the pore, while the saline cement of the sides was yet in a state of solution, and consequently fluid; and this cement being afterwards congealed by the external cold, the atom is thereby detained; and by this saline cement, which by crystalization is become hard, forms a kind of mastic which is not easily removed.
If the coloured atom, (which is as small as the little eminence that appears at the entrance of the pore, and without when the subject would not appear dyed) be sufficiently protuberant to be exposed to more powerful shocks than the resistance of the sides of the cement that retains it, then the dye resulting from all these atoms sufficiently retained, will be extremely lasting, and in the rank of the good dye, provided the saline coat can neither be carried off by cold water, such as rain, nor calcined or reduced to powder by the rays of the sun; for every lasting colour, or colour belonging to the good dye, must withstand these two proofs. No other can reasonably be expected in stuffs designed for apparel or furniture.
I know but of two salts in chymistry, which, being once crystalized, can be moistened with cold water without dissolving; and there are few besides these that can remain several days exposed to the sun, without being reduced to a flour or white powder. These are tartar, either as taken from the wine vessels, or purified, and tartar of vitriol. The tartar of vitriol may be made by mixing a salt already alkalized, (or that may become such when the acid is drove out with a salt whose acid is vitriolic, as copperas and alum); this is easily effected if it be weaker than the acid of vitriol, and such is the acid of all essential salts extracted from vegetables.
In the process of the blue vat, which I tried in small, to discover the cause of its effects, copperas and pot-ash, (which is a prepared alkali) are mixed together; as soon as these solutions are united, the alkali precipitates the iron of the copperas in form of powder almost black; the vitriolic acid of the copperas, divested of its metallic basis by its union with the alkali, forms a neutral salt, called tartar of vitriol, as when made with the salt of tartar and the vitriolic acid already separated from its basis; for all alkalis, from whatever vegetables they are extracted, are perfectly alike, provided they have been equally calcined.
More difficulties will occur with regard to the water for the preparation of other colours, such as reds and yellows. It may be denied that a tartar of vitriol can result from the mixture of alum and crude tartar boiled together; yet the theory is the same, and I do not know that it can be otherwise conceived. The alum is a salt, consisting of the vitriolic acid united with an earth; by adding an alkali, the earth is immediately precipitated, and the tartar soon forms; but instead of this alkaline salt, alum is boiled with the crude tartar, which is the essential salt of wine, that is, a salt composed of the vinous acid, (which is more volatile than the vitriolic) and of oil, both concentrated in a small portion of earth.
This salt, as it is known to chymists, becomes alkali by divesting it of its acid. Thus when the alum and crude tartar are boiled together, besides the impression which the fibres of the stuff to be dyed receive from the first of these salts, which is somewhat corrosive, the tartar is also purified, and by the addition of the earth, which is separated from the alum, (and which has near the same effect upon the tartar, as the earth of Merviels, which is used at Montpellier in manufacturing cream of tartar) it becomes clear and transparent. It may very probably happen, that the vitriolic acid of the alum, driving out a part of the vegetable acid of the tartar, a tartar of vitriol may be formed as hard and transparent as the crystal of tartar. Admitting one or other of these suppositions, consequently there is in the open pores of the wool a saline cement which crystalizes as soon as the stuff which comes out of the dye is exposed to the cold air, which cannot be calcined by heat, nor is soluble in cold water. I could not avoid making this digression.
This theory is common to the indigo vat, where urine is used instead of water; alum and crude tartar in the place of vitriol and pot-ashes. This urine vat gives a lasting dye only when used hot, and then the wool must remain in an hour or two to take the dye equally. As soon as the vat is cold, she strikes no more dye; the reason of this would be difficult to discover in an opaque metal vat, but in a glass vessel it is easily seen.
I let this little glass proof vat cool, and all the green colour, which was suspended in it while hot, precipitated little by little to the bottom; for then the tartar crystalizing itself, and reuniting in heavier masses than its moculas were during the heat of the liquor, and its solution, it sunk to the bottom of the vessel, and carried with it the colouring particles.
When I restored this liquor to its former degree of heat, after shaking it, and letting it settle a while, I dipped a piece of cloth, which I took out one hour after; with as lasting a dye as the first; so that when this vat is used and fit to work, the tartar is to be kept in a state of solution, which cannot be done but by a pretty strong heat. The alkali of the urine greens it, the alum prepares the fibres of the wool, and the crystal of tartar, secures the dye by cementing the colouring atoms deposited in the pores.
There still remains a difficulty with respect to the indigo vat, in which, neither vitriol, alum or tartar are used, but only pearl-ashes in equal quantity with the indigo, and which is pretty briskly heated to dye the wool and stuffs. But before I enter into the cause of the solidity of its dye, which is equal to that of the other blue vats where the other salts already mentioned enter, I must examine into the nature of pearl-ashes, which are the lees of wine dried and calcined: it is therefore an alkaline salt, of the nature of salt of tartar, but less pure, as proceeding from the heaviest part of the dregs of wine, and consequently the most earthy; besides, the alkali of the pearl-ashes is never as homogeneous as the alkaline salt of tartar well calcined, and there are scarcely any pearl-ashes not purified, from which a considerable quantity of tartar of vitriol may not be obtained: it is even probable by an experiment which I have related, that it might at length be entirely converted into this neutral salt; the same may be said of pot-ashes, and of all other alkaline salts, whose basis are not that of the marine salt.
The want of this homogeneous quality, is the cause that pearl-ashes never fall entirely into deliquium in the air; therefore since experience shows that there is a tartar of vitriol already formed in the pearl-ashes, it is evident that this indigo vat, which does not give a good dye until the liquor has been so briskly heated as not to suffer the hand without scalding, will dissolve the small portion of tartar of vitriol that is contained in it, and consequently this salt will introduce itself into the pores of the wool to cleanse and cement them, and will coagulate therein on the wool being taken out of the liquor, and exposed to the air to cool.
I must now give the reason why the indigo vat is green under the first surface of the liquor; why this liquor must be green that the blue dye may be lasting, and why the stuff that is taken green out of the liquor becomes blue as soon as it is aired. All these conditions being of necessity common to all indigo vats either cold or hot, the same explication will serve for them all.
1. The flurry which rises on the surface of the indigo liquor when it is fit to dye is blue, and the under part of this scum is green; these two circumstances prove the perfect solution of the indigo, and that the alkaline salt is united to its colouring atoms since it greens them, for without they would remain blue.
2. These circumstances prove that there is also in the indigo a volatile urinous alkali, which the first alkali of the pot-ash, or the alkaline earth of the lime displays, and which evaporates very shortly after the exposition of this scum to the air. The existence of this urinous volatile appears plainly by the smell of the vat during the fermentation; when stirred, or when heated, the smell is sharp, and resembles that of stinking meat roasted.
3. In the preparation of the anil, in order to separate the secula, a fermentation is continued to putrefaction. All rotten plants are urinous. This volatile urinous quality is produced by the intimate union of salts with the vegetable oil, or is owing to a prodigious quantity of insects falling on all sides of fermenting planks, and attracted by the smell exhaling from them, where they live, multiply, and die in them, and consequently deposit a number of dead bodies; therefore to this vegetable substance an animal one is united, whose salt is always an urinous volatile. This same urinous quality exists also in the woad, which is prepared after the same manner, viz. by fermentation and putrefaction, and which will be further explained in the abridged narrative of its preparation.
4. And lastly, if indigo or woad be distilled in a retort, either alone, or (which is much better) with some fixed saline or earthy alkali added to it, a liquor will be obtained, which, by all chymical essays, produces the same effects as volatile spirits of urine.
Why does not this volatile urinous quality in the indigo cause it to appear green, since it must be equally distributed through all its parts? And why does indigo, being dissolved in plain boiling water, tinge it blue and not green? It is because this volatile urinous salt is not concreted; that it requires another body more active than boiling water to drive it out of the particles surrounding it; and the solution of indigo is never perfected by water alone; whatever degree of heat is given, it is only diluted, and not dissolved in it. Indeed, this decoction of indigo blues the stuffs that are dipped, but the blue is not equally laid on, and boiling water almost instantly discharges it. I shall endeavour to answer this by an example drawn from another subject.
Salt ammoniac, from which chymists extract the most penetrating volatile spirit, has not that quick urinous smell by dissolving and boiling it in water; either lime, or fixed alkaline salt, must be added to disengage the urinous volatile parts. In like manner, the indigo requires fixed saline, or earthy alkalis, to be exactly discomposed, that its volatile urinous salt may be discovered, and that its colouring atoms may be reduced probably to their elementary minuteness.
I now come to the second quality required. The liquor of the indigo vat must be green, that the dye may be lasting; for the indigo would not be exactly dissolved, if the alkali did not act upon it. Its solution not being as perfect as it ought to be, its dye would be neither equal nor lasting; but as soon as the alkaline salts act upon it, they must green it; for an alkali, mixed with the blue juice or tincture of any plant or flower, immediately turns it green, when equally distributed on all its colouring parts. But if by evaporation these same parts, coloured, or colouring, have re-united themselves into hard and compact masses, the alkali would not change their colour till it has penetrated, divided, and reduced them to their primary fineness. This is the case with indigo, whose secula is the dry inspissated juice of the anil.
With respect to the last circumstance, which is that the stuff must be green on coming out of the liquor, and become blue as soon as it is aired, without which, the blue would not be of a good dye, the following reasons may be given: it is taken out green because the liquor is green; if it was not, the alkaline salt put into the vat would not be equally distributed, or the indigo would not be exactly dissolved. If the alkali was not equally distributed, the liquor contained in the vat would not be equally saline: the bottom of this liquor would contain all the salt; the upper would be insipid. In this case, the stuff dipped in would neither be prepared to receive the dye, nor to retain it; but when it is taken out green at the end of a quarter of an hour's dipping, it is a proof that the liquor was equally saline, and equally loaded with colouring atoms; it is also a sign, that the alkaline salts have insinuated themselves into the pores of the fibres of the stuff and enlarged them, as has been observed, and perhaps have formed new ones. Now there can be no doubt that an alkaline salt may have this effect on a woollen stuff, when it is evident that a very sharp alkaline ley burns and dissolves almost in an instant a flock of wool or a feather.
A process in dying called, by the French, fonte de bourre, that is, the melting or dissolving of flock or hair, is still a further example. The hair, which is used and boiled in a solution of pearl-ashes in urine, is so perfectly dissolved as not to leave the least fibre remaining. Therefore if a lixivium, extremely sharp, entirely destroys the wool, a ley which shall have but a quantity of alkaline salt sufficient to act on the wool without destroying it, will prepare the pores to receive and preserve the colouring atoms of the indigo.
The stuff is aired after being taken green out of the vat, and after wringing it becomes blue. What is done by airing? It is cooled; if it is the urinous volatile detached from the indigo which gave it this green colour, it evaporates, and the blue appears again; if it is the fixed alkaline that causes this green, not only the greatest part is carried off by the strong expression of the stuff, but what remains can have no more action on the colouring part, because the small atom of tartar of vitriol, which contains a coloured atom still less than itself, is crystalized the instant of its exposition to the cold air, and contracting this same colouring atom by the help of the spring at the sides of the pore, it entirely presses out the remainder of the alkali, which does not crystalize as a neutral salt.
The blue is roused, that is, it becomes brighter and finer by soaking the dyed stuff in warm water, for then the colouring particles, which had only a superficial adherence to the fibres of the wool, are carried off. Soap is used as a proof of the lasting of the blue dye, and it must stand it, for the soap, which is only used in a small quantity in proportion to the water, and whose action on the dyed pattern is fixed to five minutes, is an alkali, mitigated by the oil, which cannot act upon a neutral salt. If it discharges the pattern of any part of its colour, it is because its parts were but superficially adhering; besides, the little saline crystal which is set in the pore, whose use is to cement the colouring atom, cannot be dissolved in so short a time, so as to come out of the pore with the atom it retains.
This treatise lays down the essay of a method of dying different from any hitherto offered. I appeal to philosophers, who would think little of a simple narrative of processes, if I did not at the same time give their theory. I shall follow this method in the other experiments on reds, the yellows, or other simple colours, as it is absolutely necessary to have a knowledge of them before entering on the compound, as these are generally but colours laid on one after the other, and seldom mixed together in the same liquor or decoction.
Thus having once the knowledge of what procures the tenacity of a simple colour, it will be more easily known, if the second colour can take place in the spaces the first have left empty without displacing the first.
This is the idea which I have formed to myself of the arrangement of different colours laid on the same stuff, for it appears to me a matter of great difficulty to conceive that the colouring atoms can place themselves the one on the other, and thus form kinds of pyramids, each still preserving their colour, so that from a mixture of the whole a compound colour shall result, and which, notwithstanding, shall appear uniform, and as it were homogeneous. To adopt this system, we must suppose a transparency in these atoms, which it would be difficult to demonstrate; and further that a yellow atom must place itself immediate on a blue one, already set in the pore of the fibre of a stuff, and that it must remain there strongly bound, so that they must touch eachother with extreme smooth surfaces, and so with every new colour laid on.
It is not easy to conceive all this, and it appears more probable, that the first colour has only taken up the pores that it found open by the first preparation of the fibres of the stuff; that on the side of these pores there remains more still to be filled, or at least spaces not occupied, where new pores may be opened to lodge the new atoms of a second colour, by the means of a second preparation of water, composed of corroding salts, which being the same as those of the first preparing liquor, will not destroy the first saline crystals introduced into the first pores.
What has already been said with regard to the indigo vat, may also serve to explain the action of the woad vat on wool and stuffs; it is only supposing in the woad, that salts do naturally exist, pretty near of affinity to those that are added to the indigo vat. It appears by the description given of these vats, that the woad vat is by much the most difficult to conduct. I am convinced that these difficulties might be removed, if an attempt was made to prepare the isatis as the anil is in the West Indies. I shall therefore compare their different preparations. I have taken the following narrative from the memoirs of Mr. Astruc's Histoire Naturelle du Languedoc. Paris, Cavalier 1737, , in 410, p. 330 and 331.
"According to the opinion of Dyers, woad only gives feeble and languishing colours; whereas those of the indigo are lively and bright. This opinion I grant is conformable to reason: the indigo is a fine subtle powder; consequently capable to penetrate the stuffs easily, and give them a shining colour. The woad, on the contrary, is only a gross plant, loaded with many earthy parts, which slacken the action and motion of the finer parts, and prevent them from acting effectually.
"I know but one way to remove this inconveniency, that is, to prepare the woad after the same manner the indigo is prepared; by this means, the colours obtained from the Woad would acquire the lively and bright qualities of those procured from the indigo, without diminishing in the least the excellency of the colours produced by the woad.
"I have already made in small* experiments on what I propose, and those experiments have succeeded, not only in the preparation of the powder of woad, but also in the use of this powder for dying."
* As this ingenious man has succeeded in small experiments, it is probable he would also in the large ones; and then this plant easily cultivated in England, would well recompence the pains of the husbandman.
It is incumbent on those who have the public good at heart, to cause trials at large to be made, and if they have the success that can reasonably be expected, it will be proper to encourage those who cultivate woad, to follow this new method of preparing it, and offer premiums to enable them to sustain the expences this new practice will engage them in, until the advantage they will reap from it may be sufficient to determine them to follow it.
I shall now propose the means to succeed in Mr. Astruc's experiments, and these means naturally result from considering the method used in Languedoc for the preparation of woad, and the ingenious method by which they separate the secula of the anil in America. I have already given the preparation of this last; those who desire a fuller description may consult l'Histoire des Antilles du P. du Tertre & du P. Labat. The following preparation of the pastel, or garden woad, is thus described by mister Astruc.
The manufacturing of Pastel, or Garden Woad in France.
Peasants of Abbigevois distinguish two kinds of woad seed; the one violet colour, the other yellow: they prefer the former, because the woad that shoots from it bears leaves that are smooth and polished, whereas those that spring from the yellow are hairy; this fills them with earth and dust, which makes the woad prepared from them of a worse quality. This woad is called pastelbourg or bourdaigne.
The woad at first shoots five or six leaves out of the ground, which stand upright whilst green; they are a foot long, and six inches broad; they begin to ripen in June; they are known to be ripe by their falling down and growing yellow; they are then gathered, and the ground cleared from weeds, which is carefully repeated each crop.
If there has been rain, a second crop is obtained in July; rain or dry weather advances or retards it eight days. The third crop is at the latter end of August; a fourth the latter end of September; and the fifth and last about the tenth of November. This last crop is the most considerable, the interval being longer. The plant at this crop is cut at the root from whence the leaves spring. This woad is not good, and the last crop is forbid by the regulations. The woad is not to be gathered in foggy or rainy weather, but in serene weather, when the sun has been out for some time.
At each crop the leaves are brought to the mill to be ground, and reduced to a fine paste; this is to be done speedily, for the leaves when left in a heap ferment, and soon rot with an intolerable stench. These mills are like the oil or bark-mills, that is, a mill-stone turns round a perpendicular pivot in a circular grove or trough, pretty deep, in which the woad is ground.
The leaves thus mashed and reduced to a paste, are kept up in the galleries of the mill, or in the open air. After pressing the paste well with the hands and feet, it is beat down and made smooth with a shovel. This is called the woad piled.
An outward crust forms, which becomes blackish; when it cracks, great care must be taken to close it again. Little worms will generate in these crevices and spoil it. The pile is opened in a fortnight, well worked between the hands, and the crust well mixed with the inside; sometimes this crust requires to be beat with a mallet to knead it with the rest.
This paste is then made into small loaves or round balls, which, according to the regulations, must weigh a pound and a quarter. These balls are well pressed in the making, and are then given to another, who kneads them again in a wooden dish, lengthens them at both ends, making them oval and smooth. Lastly they are given to a third, who finishes them in a lesser bowl dish, by pressing and perfectly uniting them.
The pastel or woad thus prepared is called Pastel en Cocaigne;, when arises the proverb, Pais de Cocaigne; which signifies a rich country, because this country * where the woad grows, enriched itself formerly by commerce of this drug.
* L'Abigeois & Lauragois.
These balls * are spread on hurdles, and exposed to the sun in fine weather; in bad weather they are put at the top of the mill. The woad that has been exposed some hours to the sun, becomes black on the outside, whereas that which has been kept within doors is generally yellowish, particularly if the weather has been rainy. The merchants prefer the former; this makes little difference as to its use; it is in general always yellowish, as the peasants mostly work it in rainy weather, when they cannot attend their rural employments.
* There is a Place in India, the name I do not recollect, where the anil is prepared after the manner of the woad, and the indigo comes from it in lumps, containing all the useless parts of the plant. It is very difficult to prepare a blue vat with it.
In summer, these balls are commonly dry in fifteen or twenty days, whereas in autumn those of the last crop are long in drying.
The good balls when broke are of a violet colour within, and have an agreeable smell; whereas those that are of an earthy colour and a bad smell, are not good; this proceeds from the gathering of the woad during the rain, when the leaves were filled with earth. Their goodness is also known by their weight, being light when they have taken too much air, or rotten by not having been sufficiently prest.
Powder of Woad.
Of these balls well prepared, the powder of woad is to be made; for this purpose a hundred thousand at least are required. A distant barn or a warehouse must be procured, larger or smaller according to the quantity intended to be made. It must be paved with bricks and lined with the same, to the height of four or five feet; the walls would be better to be of stone to that height, yet often the walls are only coated with earth; this coat breaking off and mixing with the woad is a great prejudice to it. In this place the balls are reduced to a gross powder with large wooden mallets. This powder is heaped up to the height of four feet, reserving a space to go round, and is moistened with water; that which is slimy * is best, provided it be clear; the woad thus moistened, ferments, heats and emits a very thick stinking vapour.
* I can see no reason why slimy water, and yet to be clear, is preferred. It appears to me that clear river water would be more secure; with this they would avoid the inconveniences that must attend a standing water, always filled with filth; or of a muddy water, which contains useless earth, and which must make the dye uneven.
It is stirred every day for twelve days, slinging it by shovels full from one side to the other, and moistening it every day during that time; after which no more water is slung on, but only stirred every second day; then every third, fourth, and fifth; it is then heaped up in the middle of the place, and looked at from time to time to air it in case it should heat. This is the pastel or garden woad powder fit for sale to the Dyers.
Mr. Astruc, to prove that the sale of woad formerly inriched higher Languedoc, quotes the following passage from a book entitled Le Marchand. "Formerly they transported from Toulouze to Bourdeaux, by the river Garonne, each year a hundred thousand bales of woad, which on the spot are worth, at least fifteen livres a bale, which amounts to 1,500,000 livres; from whence proceeded the aboundance of money and riches of that country." Castel in his Memoirs de l'Histoire du Languedoc, in 1633, p. 49.
The comparing of these two methods of preparing the woad and the indigo may be sufficient to a person of understanding, who might be appointed to try, by experiments, the possibility of extracting a secula from the isatis of Languedoc like that of anil. It is neither the Dyer or Manufacturer that ought be applied to for that purpose; both would condemn the project as a novelty, and it would require many experiments, which in general they are not accustomed to.
I could wish this experiment was tried in great, so that at least fifty pounds of this secula might be got, that several vats might be set in case the first should fail. Whoever does try it, should be very careful to describe all the circumstances of the process. Perhaps it might not succeed at the first crop of the leaves of the woad, because the heat in June is not sufficient, but probably he might meet with success in August.
If this succeeds, there are without doubt several other plants of the same quality as the isatis, and which yields a like secula.
It is also probable that the dark green of several plants is composed of yellow and blue parts; if by fermentation the yellow could be destroyed, the blue would remain. This is not a chimerical idea, and it is easy to prove that same use might be derived from such an experiment.
There are also the bastard scarlet and the bastard crimson; but as these are only mixtures of the principal reds, they ought not to be considered as particular colours.
The red, or nacaret of bourre *, was formerly permitted in the great dye.
* This colour is given with weld and goat's hair boiled in potashes, and is a bright orange red.
All these different reds have their particular shades from the deepest to the lightest, but they form separate classes, as the shades of the one never fall into those of the other.
The reds are worked in a different manner from the blues, the wool or stuffs not being immediately dipped in the dye, but previously receiving a preparation which gives them no colour, but prepares them to receive that of the colouring ingredient.
This is called the water of preparation; it is commonly made with acids, such as sour waters, alum and tartar, aqua fortis, aqua regalis, &c. These preparing ingredients are used in different quantities, according to the colour and shade required. Galls are also often used, and sometimes alkaline salts. This I shall explain in the course of this treatise, when I come