White and green pigments are made and distempered as follows. Put little rods across the top of a vessel filled with very strong vinegar, and lay sheets of Iead or copper on them. Then close the vessel up carefully, and Iute it with clay or plaster or wax, so that no vent may remain through which evaporation might take place. Then after thirty days the vessel is opened, and the copper will be found all green, but [the lead], white, from the acidity of the wine. When you have taken it up and dried it, grind the white with wine, and paint with it upon parchment. But for woodwork and walls it should he ground with oil. In the same way, grind and temper the green with oil; for woodwork and walls with wine, or if you prefer, with oil. For either is good. But for books you should not grind it, but let it soak in good wine, white and very clear, or in vinegar; and then rub it a little with your finger, and immediately all the wine will become green. And if the wine is very green before all the dregs are dissolved, you will know that there is enough of the powder in it. But if it has a poor colour, and looks as if it were contaminated with yellow, you will know that there is not enough of the powder in it; so add a little more, and Iet it stand for a while, and then rub it again with your finger. And repeat the operation a third time. Then throw out the dregs, and put the very clear green into a little copper vessel; and if you wanted to write with it at once, you could not do so unless you Iet it simmer on the fire, to thicken it. And that is as much as to say that it must be put to thicken, either shaded from the sun, or in the gentle breeze of dawn or evening, but only when the wind is blowing softly, and not in direct sunlight.