302 Painting. IV. Materials. Having thus given a slight outline of the leading prin- ciples of the theory of painting, we will briefly enumerate the materials and processes employed in its practice. In speaking of the materials we must distinguish between those painted on, and those painted with. For drawing, crayons of different kinds are used; for painting, a brush to hold the colour. 1. For drawing on paper, parchment, ivory, or other similar substances — pencils, chalks, charcoal, and water colours are used. 2. For painting on wood and canvas — tempera or dis- temper, and oil colours. 3. For painting on wall surfaces, dry colours, tempera, wax colours, and fresco colours. The so-called lead-pencils employed in drawing do not contain any lead ; but are made of graphite or plumbago, an opaque greyish-black mineral with a metallic lustre, somewhat greasy to the touch, which produces a clear stroke of any thickness required, and peculiarly suitable for rapid sketching on account of the ease with which it may be effaced. Blade chalk is a bluish or greyish-black material, used both for drawing and as a colour in painting; but it is neither easy to work with nor pleasant to handle, and charcoal is preferred to it for all but small sketches. The scarcity of coloured chalks has led to the use of pastel, or chalk mixed with various colours and made into crayons, but it is not very durable, and if pictures in it are washed with gum to preserve them, they lose the soft, warm appearance which is their chief charm.
