Canvas is now generally used for painting in oil. It is kept at the artist's colourman's ready primed, of various widths, and but a few hours notice is required to fix it on a frame of any dimensions. Certain sizes are always kept on hand, ready mounted on frames or stretchers, fitted with wedges in the corners, so as to be between the tenon and mortice of each side, so that by driving in the wedges the canvas can be tightened. The fineness of the cloth should be proportioned to the size of the picture, and the subject to be painted. For a cabinet piece the surface cannot be too smooth. The cloth should be free from all irregularities. The ground should be moderately thin, evenly laid, and without streaks. The best ground is nearly white, or of a light cream colour; these help to give a transparency to the work.,