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PRACTICE has already experienc'd so many ways to bring this fine Enamel to the most advanced Improvements, that 'tis impossible to expect any greater; and for such as wou'd make it, they may proceed boldly thus.
Set six Pound of Crystal ground, as in Chap. 163. in a glazed Pot at the Glass-house Furnace to melt and cleanse; then cast into it at four several times in∣termitting, four Ounces of Calx, as prepared of
Lead and Tin, in Chap. 148. stir the Matter very well at each time until it incorporate, then let it all purge for a while, and cast it Ladle-full by Ladle∣full into Water, and again put all into the Pot to melt and refine anew; after this add to it an Ounce and half of red Copper pulverized and calcined, as in Chap. 33. which will tinge the whole of a deep Colour, but cast it in at three Intervals, and stir it very well to incorporate; two Hours after, add to it at thrice, an Ounce and half of Crocus Martis, given in Chap. 24. mix it well as before, and let it remain to refine about three Hours, then throw on it six Ounces of Tartar calcined, as in Chap. 57. Chimney∣Soot vitrified one Ounce, Crocus Martis again one Ounce and half pulverized, and all well mixt at four several Intermissions, and Quantities, stirring the Metal always with the Iron-Crook, lest it swell or boil over: After this let it repose and purifie about three Hours, stir it again and try the Colour, if it be red as Blood it's right, if not, add at discretion, a little more of each of these Powders of Tartar, Soot, and Crocus Martis, until the Colour be full and true, and so let it stand for a whole Hour, and try it again; if you find it perfect, proceed no further, but keep it for use, 'tis very proper to apply to Gold for Ena∣mel.