CHAP. CCIII. To make White-Ground for Painting on Glass.
NOW to pursue our Work, we will begin with the Preparation of all the Colours to be used in Painting Glass; for before we proceed to pre∣scribe the Rules, how to work the Materials must first be considered.
The White is compounded of several Ingredi∣ents: The first are small White River Peble-Stones heated red over a Fire, in an Iron-Ladle, and thrown afterwards into an Earthen-Dish full of cold Water to calcine them, and this must be repeated several times, until they be prepared; afterwards being dried, pound them with a Stone, or Glass-Pestle in a Stone-Morter, and so grind them upon a Marble to an impalpable Powder; then mix a fourth part of Nitre with it, and calcine them in a Crucible; then pound and grind them again, and calcine them a third time over a smaller Fire than your former, and so take them off for Use.
This done, when you would Paint with it, add equal parts in weight of Gip, a sort of Talc found among Plaster-mold baked on the Coals to a White∣ness, and reducible to Powder, and Rocaille, where∣of we have already spoken, grind them all three very well together in a hollow Plate of Copper, with Gum-Arabick Water; thus have you your White in good condition to Paint withal.