There are two kinds of grounds with which they [canvas, panels and millboards] are all prepared, namely, the hard, or oil ground, and the absorbent ground; which latter is so called from its tendency to absorb a portion of the oil from the first lay of colour that is put on it; an advantage (if it be one) which is not perceptible in any subsequent application of colour to the picture, and therefore either ground may be chosen. A well prepared canvas should have the ground laid without streaks, and moderately thin, so that the texture of the cloth should be scarcely, or not at all, perceptible, and it should be free from projecting coarse threads and knots; panels are always preferred with a smooth surface, as they are mostly used for smaller works that are intended to receive high and delicate finish. The ground with which millboards are prepared, has frequently a slightly granulated surface, this being better calculated to receive, and give effect to, the bold and broad style in which sketches and studies for pictures are usually painted, and for which millboards are chiefly used.,,