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. LXIV. To make an Amethist-Colour in Glass.

AMethist being of a Violet Colour, proceeding from Red and Blue, must be well imitated to look beautiful. For this Colour, take Crystal Fritt well made, with Tarso and not Sand, this Colour re∣quiring no other; to which add to each Pound one Ounce of the following Powder, which mix well to∣gether before they be put into the Pot. After that you must set the Pot to the Fire in the Furnace little by little, otherwise the violence of the Powder would cause it to break. When this Glass has been well purified for the space of four Days, and it has the colour of Amethist, you may work it. This Colour may be augmented or diminished by means of the Fritt, or Powder, according to the Discretion of the Workman.

This is the Powder which produces the Amethist Colour in Glass. Take one Pound of Manganese of Piedmont, prepared as in Chap. 18, and an Ounce and half of Zaffer, prepared as in Chap. 17; mix them well together, and put the Dose we have shewn to each Pound of Fritt, to have a true Ame∣thist-Colour.

Porta in his sixth Book, Chap. 5. only allows one Drachm of Manganese to each Pound of Metal, to make the Glass of an Amethist Colour; but that Dose is too weak, and you must follow that we have shewn.