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. XXII. Another Way of making Ferretto of only Copper, for Tinging Glass.

NEri and Merret give the Name of Ferretto of Spain to the following Preparations, in this and the next Chapter; asserting that it communi∣cates several very fine Colours to Glass. The diffe∣rent ways of Calcining Metals, causes different Ef∣fects; which is known to the Experienc'd in this Art.

If the Ferretto we have taught in the precedent Chapters, be of vast use in Glass, and very ser∣viceable in Pastes, Enamels, and Glass of Lead, by reason of the great Resemblance it causes to Preci∣ous Stones; this and the following are of no less use.

Take thin Plates of Copper or Brass, cut them into pieces, and put them into a Crucible, in the Bottom of which you have laid a Bed of Sulphur pulveriz'd, then a Layer of Copper; then another of Sulphur, and then again of Copper: which you must thus continue stratum super stratum, till the Crucible is full. Then cover over the Crucible with another, or with a Tile, and lute it well, and dry it, and put it in∣to a Furnace among hot Coals in a good brisk Fire for the space of two hours. Then take out the Crucible, let it cool, and you will find the Copper or Brass calcin'd, which will break and crumble between your fingers like dry earth, of a blackish Colour. You must pound it to a fine Powder, and searce it and keep it in a Vessel well closed for use.