First, then, to prepare a ground with oil, select a half-primed canvas that feels slightly rough to the hand; the more tooth the better. Mix ordinary flake white, two parts; whitening or finely ground chalk, one part. Add a small quantity of linseed-oil (sufficient, perhaps, to restore the mixture to the original consistency of the thick flake white). If you wish to use this ground thinly, or if, while working it, it becomes thick by evaporation, add spirits of turpentine. By this means you can reduce it to any degree of thinness you require. Always remember, however, that the linseed-oil is used not only to mix the colour and make it work, but also as a cement to bind the particles of colour together; while the turpentine will evaporate so entirely, that were you to use powder colour with spirit only, it would,when dry, all rub off. Again you must guard against using too much oil, as this frustrates the whole intention of the ground. The oil rising to the surface dries in a hard glaze, and thus renders the ground non-absorbent for the after-painting. Mix your ground in a plate or dish, and apply it to your canvas with a large brush, painting it firmly and rubbing it well into the canvas. If the surface when dry is too rough or uneven, go over it again with thin colour (liquified with turpentine). By putting the colour in a gallipot, and covering the jar with a wet cloth, it will keep fit for use for several days.*,,* There is an absorbent white ground prepared with oil for use in this manner by a man named Davy, and known as 'Davy's White.' It appears to be a very useful and safe preparation. In using it to prepare canvases if it is too thick for your purpose, add a small quantity of turpentine to the colour.,