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. CXI. The Way to make very hard Pasts with Sulphur of Saturn, and to give them all the Colours of Precious Stones.

THIS Paste is a Consequent of the precedent O∣peration, because we employ therein the same Sulphur of Saturn, we just now mentioned; and that which chiefly causes its Beauty, is that all the Ingre∣dients we use in it are perfectly purified.

To do this, take ten Pound of Natural Crystal prepared, with six Pound of Salt extracted from Polverine of Rochetta, purified, pounded, and well searced, as we have shewn in Chap. 7, whereunto add two Pound of Sulphur of Saturn chymically prepared, as in the preceding Chapter; then mix these three Powders well together, and put them into an Ear∣then glazed Pan, and cast on them a little common fair Water to reduce these Powders into a Lump something hard. Afterwards divide them into seve∣ral Parcels of about three Ounces each, making a hole in the middle the better to dry them at the Sun; being well dry'd, put them into an Earthen Pot well luted, then calcine them in a Potters Furnace, then pound and grind them well on a Marble, and searce them through a fine Sieve. This being done, put this Powder into a Glass Furnace, there to melt and purifie for three Days; then cast the Matter into the Water, as we have elsewhere shewn; and after you have dried it, put it again into the Pot in the same Oven, there to melt and repurifie for fifteen Days, that it may be without spot, and that it becomes of the colour of Precious Stones.

This Crystalline Matter may be tinged of several Colours, viz. Emerald by means of Copper thrice calcined; Topaz by means of prepared Zaffer; and so of others whereof we shall not treat here, having largely done it elsewhere. To succeed, you must put into the Furnace as many Pots as you design to make different Colours, add to each as much Chry∣stalline Matter as you please, and regulate accord∣ing to the weight of the tinging Materials which you add to them, and proportionate them to those we have described in the precedent Chapters of this Book. This Paste will have finer Colours than the true Natural Stones, and approach near to their

hardness; particularly that of the Emerald, which the Curious will find by Experience.