Point XV

If Shoemakers put old Iron to this subject, they may therewith adorn their Leather with an excellent Black.

If Nitre be dissolv’d in Vinegar, and old Iron lie some time in it, it will make an Ink with which Hides may be blacked with an excellent Black. But there is no need of Nitre for this use, for if Iron be put to Aqua Calcis, it effecteth the same thing; only mention is made of this in Miraculum Mundi, that it might be manifest, that this Universal Subject may be of use, to all and singular Artificers.