It is advisable to purchase your canvas many months before using it; a year indeed is none too long. Keeping it then where it will be exposed to the air, and the light, and even to the sun if not too warm, the priming of the cloth has a chance to become perfectly dry, and thus the oil, wherewith it was prepared, is less likely to add its pernicious effects to those of the oil which you yourself are obliged to use. Before using it, rub it over with pumicestone (putting your left hand behind the cloth, so as to prevent injuring it), and wash it off with water, to which may be added a portion of alcohol. The fineness of the cloth should be proportioned to the size and subject of the picture. You cannot have too smooth a surface for a small cabinetpicture which will be examined close at hand; whereas in one of large dimensions this is less necessary, and a canvas somewhat courser is even preferable because it holds the paint better. The great essential is that the cloth be as free as possible from knots. If these be covered, make no objection to the thinness of the priming.,