On folium. There are three kinds of jolium: one purple, another red, and a third sapphire. You temper them as follows: take ashes and sift them through a cloth, pouring cold water over tbem, and then make little cakes out of them, like loaves of bread, and put them in a fire until they glow all over. After they have glowed for some time with the heat and then cooled off, put a portion of them into an earthen vase, drench them with urine, and stir them with a stick. And when they have settled, moisten the red jolium lightly with them and grind it a little on the stone, adding to it four parts of quicklime. And when it is ground, and strong enough in colour, strain it through a cloth, and lay it on with a brush. And if you wish to represent a robe on the page of your book, design it with the quill, using purple folium and the same medium, only without the quicklime.