Chapter XXVIII A Recipe for Making Another Sort of Gilding Colour
Take red chalk,179 verdigris, saltpetre, vitriol,180 and salts of ammonia, but half as much of the first as of the other ingredients; take each by weight, and pound each separately; and be careful to pound them very fine; when pounded stir them up in clear water to the consistency of a paste, and while you are stirring see that you go on grinding them up till all the particles are well blended. This done, you must put them in a rather big vase because the composition bubbles up; and mind that the vase has a glazed surface, or better still be of glass, and let it be corked. In order to put the colour on, your work must needs be thickly gilded, or else it will turn black, for this colour is very powerful. But if it be sufficiently strongly gilded the work will colour beautifully. The colouring stuff is applied with a paint brush, but you must mind not to touch the silver or you will black it. Painted over in this wise you set your work to the fire, give it a good steaming and dip it into fresh water, but you must mind not to overdo the steaming or the gold would be eaten away and not hold.
Footnotes
179 Matita rossa.
180 Vitriuolo: probably green vitriol, i.e., sulphate of iron.