The art of glass shewing how to make all sorts of glass, crystal and enamel : likewise the making of pearls, precious stones, china and looking-glasses : to which is added, the method of painting on glass and enameling : also how to extract the colours from minerals, metals, herbs and flowers ... : illustrated with proper sculptures / written originally in French, by Mr. H. Blancourt, and now first translated into English ; with an appendix, containing exact instructions for making glass-eyes of all colours.

CHAP. XXXVI. Another better way of making Aes ustum.

CUrious Gentlemen who employ themselves sometimes in Chymistry, and do not grudge their time and charge as the Workmen doe who get thereby their lively-hood; have far finer and more In∣genious preparations of aes ustum, which render it of greater virtue, and more Power to tinge, We will only give the reader one of them.

Take thin Plates of the Reddest Copper which is the hardest sort, make it red-hot in a Crucible or otherwise, then extinguish it in a Lee of Urine, wherein common Salt has been dissolved; and reite∣rate this process till the Copper become of the colour

of Gold both within and without. After that you must cement those Plates with two parts of Sulphur, two parts of Salt-Petre, and one part of Vitriol cal∣cin'd ad rubedinem, the whole reduc'd to powder, wherewith you must stratifie those Plates in a Cruci∣ble, pressing close each Layer or Row; then you must cover it with another Crucible mouth to mouth, the upper having a hole bored at bottom, then lute them well together. The Lute being dry put the Crucible in a * 1.1 Round Fire during six hours, and hot ashes underneath. The first two hours the fire must be one foot distant from the Crucible the two second hours one half foot nearer; and the two last hours quite close covering the Crucible; You must take special care that the matter does not melt, and that the fire be not too great, for that would spoil all. The Crucible being cold, you must take it out, and emptying the matter pound it well; this is what we call Aes ustum. To make it fit for use you must wash it, to take away the Sulphur, and then dry it and keep it in a close Vessel.

There are other curious Persons who make an Aes ustum yet finer than this, and more penetrating in Colours; but the preparation is more costly and requires more time; for instead of Brimstone and Salt-Petre they make use of a purified Sulphur and fixed with Sal Armoniac; and instead of ordinary red Vitriol they use Roman Vitriol which they pre∣pare with Lee of Urine, and a fusil Salt, which after∣wards they put in a reverberatory. But since the others serve well enough for colouring Glass, and are easier to make, we shall not here give you the preparation of this last which would be too long, and being more serviceable to several other purposes which Experience testifies.

Notes

• * 1.1

  Wheel-Fire.