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. XXXIII. To make Copper thrice calcin'd for colouring Glass.

THE same red Powder in the preceding Chap∣ter serves here. Take of that Powder and put it on Tiles, and calcine it again in the Furnace four days; it will become black, and coagulated into one Mass: Powder it and searce it, calcine it again 5 or 6 days in the same Furnace, and it will become grey without coagulating any more, or running into Lumps, and will be in a conditi∣on fit to be dissolv'd. Of this Powder which the Italians call Ramina di Trecotte, is made Sky-colour'd blue, the colour of Turcois, the green of Emerald,

and several other colours. It must not be calcined above thrice, for it would no longer Colour Glass. You may know if it be calcined well, by casting some of it in a Pot of boiling Glass; if it swells as we have said before, if not, you must set it yet Twenty Four hours longer in the Furnace, or rather begin a new Process.