CHAPTER XXXI.
HOW GOLD AND SILVER ARE LAID IN BOOKS.
Afterwards take pure minium (red lead), and add to it a third part of cinnabar (vermilion), grinding it upon a stone with water. Which being carefully ground, beat up the clear of the white of an egg, in summer with water, in winter without water; and when it is clear, put the minium into a horn and pour the clear upon it, and stir it a little with a piece of wood put into it, and with a pencil fill up all places with it upon which you wish to lay gold. Then place a little pot with glue over the fire, and when it is liquefied, pour it into the shell of gold and wash it with it. When you have poured which into another shell, in which the purifying is kept, again pour in warm glue, and holding it in the palm of your left hand, stir it carefully with the pencil, and lay it on where you wish, thick or thin, so, however, that there be little glue, because, should it exceed, it blackens the gold and does not receive a polish; but after it has dried, polish it with a tooth or bloodstone carefully filed and polished, upon a smooth and shining horn tablet. But should it happen, through negligence of the glue not being well cooked, that the gold pulverizes in rubbing, or rises on account of too great thickness, have near you some old clear of egg, beat up without water, and directly with a pencil paint slightly and quickly over the gold; when it is dry again rub it with the tooth or stone. Lay in this manner silver, brass, and copper in their place and polish them.
The raised gold was not always produced by the mixture of red lead and white of egg recommended by Theophilus. It was, especially in Italy, frequently made of a composition of "gesso," or plaster, and in the 15th century was often punctured all over by way of ornament. It may be occasionally met with stamped over in patterns, with intaglio punches. This "gesso raising," though very brilliant, possessed little tenacity, and in many examples it has scaled off, while the more ancient "raising" prescribed by Theophilus has adhered perfectly.