To soften horn

Take urine which has stood covered for four weeks, and put in a pound of unslaked lime and half as much weyd ashes, or ashes of wine lees, eight loth tartar and as much salt, and mix everything well together. Let it boil well, pour it then in a lye sack and let it run through twice. Keep this lye well covered, and when you want to soften horn, let it lye therein eight days and it will become soft.

Or take poppy stems with their tops, burn them to ashes, make a lye from this, and let the horn boil therin.

Citation Type  Wood/Bone/Horn Dye Recipe
Citation Year 1532