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. CCXXXIV. How to incorporate the Powder of Lapis-Lazuli with the strong, or weaker Cement.

WE have given in Chap. 228. the way to pre∣pare the Powder for mixing with the Ce∣ment, to extract the Colours; we now come to shew how to mix it with the Cement, in order to extract the Vltra-marine from them for Painting.

Take a Pound of the Powder, and the like quan∣tity of Cement assigned in Chap. 231. observing al∣ways to take the first that was workt with the Hands; cut the Cement small, and the pieces being a little wet, put them into a glazed Earthen-Pot, o∣ver a Fire of red-hot Ashes, to melt, and take care it does not boil; if it should, you must prevent the the damage which it might cause, by putting in some Linseed-Oyl. The Cement being thus melted, anoint all your Spatula over, from the Handle downwards, with the same Oyl, and so put in the Powder by ve∣ry little quantities, and taking a great deal of time, that they may the better incorporate; and be sure to stir it all the while very well with the Spatula, so as to make it all alike, until it become like an Oynt∣ment, or Salve; then off with the Pot, and throw the Stuff boiling hot into an Earthen-Bason of cold Water, and at that very instant take off all that sticks to the sides of the Pot; when 'tis cold enough to be handled, if it appears well coloured, 'tis a sign you have work'd it well: This done, rub your Hand with Linseed-Oyl, and work it as they do a Paste of Bread, or Dough, for one Hour, that it may be

throughly compact. The longer you work it, the better and easier the colour may be drawn; after∣wards make it up like a Loaf, or Brick, and set it in an Earthen-Dish to dry, pouring thereon some fresh Water; let it steep for fifteen Days, the longer the better for extracting the Vltra-marine.