125 - Rosichiero for Gold by Another Method
Take crystal frit, made as described in the above recipe for rosichiero [chapter 124]. Fuse 4 lbs of this frit in a clean glazed crucible. When it has clarified, throw it in water. Heat it again, leave it to clarify, and throw it in water a second time. Then reheat, and leave it to clarify.
When it is well clarified, add the purified calx of Iead and tin, described in the above recipe for rosichiero, add this calx little by little, ½ oz at a time, Iet the calx incorporate, and watch for when the glass becomes an ash gray color, at which point it will be good. Do not add too much calx because if you overload it with calx it will become white in color, which is not good.
When it turns the said gray color, do not add more calx, but leave it to clarify. Then have 2 oz fine minium, add this to the glass, and Iet it incorporate weil, and clarify. When it clarifies well, throw into water, return it to the crucible, and leave it for 8 hours. Have ½ oz of calcined copper, that is to say red copper, as was described in its place [chapter 22], and ½ oz of raw white [wine] tartar.
Throw these things in, and stir them well. Now add a dram of hematite, which the sword makers use for burnishing, and 1 dram of fixed sulfur [chapter 126]. Stir and incorporate these powders, and watch. lf it is over-coloured, give it a little manganese to dilute it. lf it is clear of colour, add more of the fixed sulfur, hematite, a little red copper, and a little white wine tartar at your discretion so it becomes the desired colour.