As for these 13 Metallick Labours, they are in themselves very good, and profitable to be known by every one handling Metals, some of which, if they be accurately manag’d, and by a skilful Artist, will afford great Gain, and they are all done by the help of the Salt of the Earth. But I will not deny, but that those Labours may also be performed by another way, which needeth no Nitre. But I do not now intend to say any thing of that, but only to prove that all those Secrets and Transmutations may be effectually performed by the contemptible salt of the Earth.
In Mechanicks.
Point I.
They who Engrave or Etch upon Copper, may of this subject prepare a good corrosive Water, by which (the Copper Plates being first smeared over with a Covering fit to defend them, and what Images or Lines they please, drawn upon them, with a stile or stift) by an easie and compendious manner, they will be eroded or eaten, which otherwise would require a long time to be engraven.
That a corrosive and graduating Aqua-fortis may be prepared of Nitre by destillation, needs no proof, the way of making it being every where known, as a thing common, only here it is proved, that this shortening of the Engraver’s Work may be performed by the Salt of the Earth.
Point II.
Painters by the help of this, may prepare for themselves most excellent Colours, as Ultra-Marine, blue Smalt, fine red or Scarlet Lacca, Venice Ceruse, and others necessary for their Uses, which otherwise they must have from far, as Italy, Holland, France, &c. and at a dear rate.
That excellent colours for Painting, may be made by the salt of the Earth, I will thus prove: Blue Smalt is otherwise prepared of flowing Sand, Chalcitis, and Potters-ashes: But if instead of those ashes, you take the fixed salt of the Earth, the smalt will not be only rendred more open, loose, and fine, but also purer, by reason the salt of the earth is purer than those ashes. Lacca for the most part is made of Flocks shorn from crimson or scarlet cloth in the dressing, and by a singular lixivium (instead of which Nitre may be taken) the colour is extracted, which is to be precipitated, edulcorated, and dryed upon clean Boards in the sun, or by a stove. Verdigrease and Ceruse are commonly prepared by the help of Vinegar, in Iron Vessels put in Horse-dung; but if the Copper or Lead be dissolved in spirit of Nitre, and the Copper precipitated by a lixivium of salt of Tartar, but the Lead by salt water, then edulcorated and dried, the Copper will exhibit a green colour, which may be used in all Paintings, and will not corrode and destroy other colours, as the common Verdigrease is wont to do: And the Ceruse is rendered more delicate white, and pure than that which is prepared by Vinegar, with which oftentimes much Chalk is mixed to augment it, and is not so conducible to Painting, nor to the shops, as that which is made per se, without any mixture.