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_.