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. CLXIII. The Way to make a Crystal-Ground for our Red Enamel.

THE Red requires a Chrystal more lasting than any of the former, therefore we will give you a Composition here sufficient for that purpose.

Take twenty four Pound of Salt of Polverine, Ro∣chetta, or Soda prepared as directed in Chap. 5. and six pound of Frit, as in Chap. 6. these mixt and finely powder'd, must be steept in Water to bring the Mass into a Body like Paste; and then make it up into small thin Cakes, lay them on Tiles in a Lime-kiln, or Potters-Furnace for six Hours to calcine, or near the Glass-house Furnace Vault, or on the Upper Vault, taking special care that they don't melt, let them re∣main there for three or four Days, or until they be very well calcined.

This done resolve them into an impalpable pow∣der, adding thereto four pound of Calx of Lead and Tin prepared and calcined according to directions in Chap. 148. and Chap. 81. four pound of White calci∣ned Tartar, prescribed in Chap. 5. and elsewhere. These being all mixt and very finely pulverized, put them them into your glazed pot at the Glass-house Furnace to melt and refine; thence throw the Metal into Water, and again (when dry) into the pot to melt; cast it a second time into the Water, and dry it, let it melt and refine over-again in the pot for some Hours, and 'twill be fit for use.

Consider always the Lead which is among the o∣ther Ingredients, and be very careful that you let none of it remain in the pot when you throw the Matter out into the Water, for it will be apt to pre∣cipitate to the bottom, and this for several Reasons elsewhere given, too tedious and needless to be here repeated.