The treatises of Benvenuto Cellini on goldsmithing and sculpture

First I will talk of that mixture with which you etch on copper instead of cutting with the graver, this is an easy and a very beautiful method. Aquafortis for etching is made thus: you take half an ounce of sublimate,[195] one ounce of vitriol, half an ounce of rock alum,[196] half an ounce of verdigris, and six lemons; and after having care to pound the first mentioned substances well, you boil them a little in the lemon juice, but not so as to let them get too dry. The boiling should be done in a glazed pot, and if you have no lemons you may take strong vinegar which will give a like result. When you have well smoothed your copper plate you can take any ordinary varnish,[197] such as is used for the lacquering of the ornaments on daggers and other iron work, & heat it gently, putting a little wax with it, this you do to prevent the varnish from cracking when you draw upon it. It must not be too hot when you spread it on your copper plate. When you have etched on your design make a ridge of wax round the plate and pour on the parting water, letting it stand not longer than half an hour. If then it be not bitten deep enough, do it again. Then remove it and clean it well with a sponge. You draw on the varnish with a stylus of well tempered steel, that is an iron needle, which in the craft is termed a stile. You wash the varnish off the plate with a sponge of warm oil, but very softly so as not to destroy the intaglio. Then you use the plate & stamp impressions on to card-board from it in just such a manner as plates done with the graver. It is true that this sort of plate is produced very easily, but then, you see, they don’t last near so long as those done with the graver.