The canvas being streched on a frame, you must give it a layer of size, or paste water. When dry you shall go over it with a pumice stone, to smooth off the knots. When the cloth is dry, a layer of oker must be laid on, sometimes mixing with it a little white lead to make it dry the sooner. When dry you will go again over it with the pumicestone, to make it smooth. After this, a second layer, composed of white lead, and a little charcoal black is sometimes added, to render the ground of an ash colour; observing in each manner to lay on as little colour as possible. As little oil is to be used as possible, if it be desired to have the colours keep fresh; for this reason some mix them with oil of aspic, which evaporates immediately, yet serves to make them manageable with the pencil.,As to oils, the best are those of walnuts, linseed, aspic, and turpentine. The desiccative or drying oils, are a nut oil boiled with litharge and sandarach; others with spirit of wine, mastich, and gumlacca. The next operation is to draw the design on the canvas; and afterwards to prime the work, which is done by laying a lay of white all over it, except on the lines of the draught, which must be kept visible.