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. LXV. To make Glass of a Saphir-Colour.

TO imitate the Colour of Saphir in Glass, which is of a clear and transparent Blue; you must put to each hundred Pound of Fritt of Rochetta, one Pound of Zaffer prepared, with an Ounce of Manga∣nese of Piedmont, also prepared as we have shewn. Well mix these Powders with the Fritt, then put the whole into a Pot in a Furnace, letting the Glass be well melted and purified: For the longer it remains on the Fire it becomes so much the siner, if you take care to take it out from time to time. Then mix it very well, and make an Essay of the Colour, and if it be not full enough, augment or diminish it as much as you think fit; then the Glass may be wrought, and you will have a Saphir of the Colour of the Dou∣ble Violet of Constantinople, which the small Dose of Manganese produces.