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. CXLVIII. To prepare the Matter for Enamel.

NOW we proceed to shew the Ingredients by which the principal Matter for Enamel is pre∣pared, before the Colours can be applied, of which we shall give Directions in the following Chapters.

Take Lead in Piggs thirty pound, Plate-Tin of Cornwall, thirty three pounds; mix and calcine them as directed for Lead in Chap. LXXXI. pre∣cisely observing the Directions there laid down. This done, fearce the Calx, and put it all into a glazed Earthen Pot, fill'd with Water, put it over a fire, and let it boil a little; then take it off, and pour the Water gently into another Vessel, which will carry along with it the more subtile Calx. Repeat this until no more of the Calx can be subtiliz'd; which you may discover by the Pureness of the Water in pouring it out of one Vessel into the other. After this calcine the Remains of what is in the first Pot, as before, and thus continue to calcine and subtilizetill you can get no more of the subtile Calx. Lastly, put the Waters out of all your Receivers into larger, and set it on a slow Fire to evaporate. The Fire must be very gentle for this Reason, that the Calx do

not founder or fall to the bottom, but continue more fine and subtile, than when it was first calcin'd.

Your Calx being thus prepared, take thereof about fifty pound, and as much Fritt of white Tarso beaten and searced, as directed Chap. VI. To these add eight Ounces of Salt of Tartar, finely searced and prepared as in Chap. XV. Mix all these Powders very well together in a Pot, and let it stand in the Glass-house Furnace or Oven about ten hours to digest and purifie. Then take them out, and reducing them to an impalpable Powder, keep it in a close dry place for use. Thus must your Matter for E∣namel be prepared to receive the Colours, but of that more hereafter.