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. LI. Wherein is shown the art of making Chalcedony of the Colour of Agats and Oriental Jasper; with the way to prepare all Colours for this purpose. To make Aqua-Fortis and Regalis, necessary in this business. The way of preparing and calcining Tartar, and u∣niting it with the Red Colour of its own kind called by the Italians Rosichiero, which produceth Glass of many Colours with undulations in them very plea∣sant to behold, and gives it an Opacity like Oriental Stones.

BEfore I proceed to the Explication of these preparations, it will be necessary to shew those of some Minerals used for such Com∣positions. And although one may buy several of them Publickly, ready made, yet our design being

to make this work as perfect as we can, it will be necessary that we shew the Chymical way of prepa∣ring them after the best manner, by which the curious in this Art may do it themselves for less charge than they can buy them. There is no doubt, but that the Metalline matters made use of to tinge Glass, may give it several colours more lively and brighter than any it receives in the or∣dinary Furnaces, when these matters are artfully prepared, and their Metalline Colours are choice∣ly pick'd out and Collected, and well purified from Heterogeneous matters which hinder the communi∣cation of their Tincture to the Glass. The colour of Chalcedony, or rather the matter whereof it is made, is nothing but an Amassement of Several Colours which may be made in Glass, and which many are not acquainted with. We will shew the whole process and the way of well succeeding in it. It is most certain that all the Colours we can extract will never give that Beauty and Splen∣dor to Glass which is desired, if they be not well prepared. You must therefore for this purpose well calcine and dissolve the metals with Aqua For∣tis. You must open the Copper, Sulphur, Vitriol and Sal Armoniac and other minerals with a great deal of patience, and prepare them at a gentle Fire, the violence of the fire being very noxious in this affair as well as in others, which very often ren∣ders Operations defective, which otherwise would succeed well, among those who are impatient or ignorant. You must observe Regularity in all those Cases we shall treat of, and exact proportions of the Doses, and put them in, in fit and due time, otherwise the Process will miscarry; especially in the Red Colour whereof we treat in the 8th Book, and in the Tartar that it may be perfectly Calcin'd. You must yet further observe that the Metal be

well Boiled, well Purified, and made fit for Work∣ing; then proceed in it as diligent Workmen ought to do. Thus you may perfectly imitate Agat, oriental Chalcedony, with the Fairest and most Beautifull Colours, and wavings, so lively and full, that it will seem as if nature her self could not arrive to the like perfection, or art imitate it. Yet experience shews us that in several things, and in particular in this Art of Colouring Glass, that Art cannot only imitate nature, but also far sur∣pass her. The Eye and Phancy shall be judge, in the three ways which we will shew, where every thing shall appear so distinctly, that the curious shall easily understand it, and all that will apply themselves to it may succeed therein, if they do not deviate from these precepts. If they are well put in practice, you'll find more than we can tell you.