A simple example may be found in the works of Pissarro ; in all his pictures painted between 1878 and 1885 approximately, a mixture of Veronese green and ultramarine can clearly be dis tinguished. The use of these two colours during the period in question is thus established. This example has been selected be cause Pissarro obtains highly characteristic effects by this means. The remainder of his palette could easily be ascertained by con tinuing the analysis. Although, however, analysis may be simple in the case of the Impressionist school, it becomes more difficult as we go further back in the history of painting. The present writer frankly confesses that he cannot himself read the palette of all painters from their works. It is, however, possible to derive one general conclusion from a close study of the works of the great masters : that it is not necessarily the number of colours used which makes the colourist.
The grinding of the colours is a long and somewhat difficult business. It consists in pounding the powder, moistened with oil, until the grains are so fine as to be imperceptible. (See COLOUR MILLS.) This is done with a heavy muller, the under surface of which is as smooth as the slab of granite, on which the colours are ground. From time to time the grinder adds a few drops of oil. He has to continue kneading the paste until it is of the re quisite fineness and consistency. It should be noted that a colour which reaches different grinders in the same state of chemical purity may not be of equal quality when it leaves their hands ; the cleanliness with which the operation is carried out and the quality of the oil used affect the final result. The manufacture of colours is not a simple operation. Great practice is for example necessary to bring cobalt blue to the right consistency. Oil alone will not bind the paste sufficiently, and wax has to be added. The kind of oil used has its importance ; olive oil, which was formerly much used in Italy because of its abundance, has now been given up because it dries slowly. Linseed oil on the other hand dries rapidly; copal oil is much esteemed by certain manufacturers; but poppy oil, which is light and colourless, is by far the most frequently used.
The painter should be able to use the paints in the form in which they reach him. He may use a siccative to make them dry more rapidly, but he should remember that this is an evil, even if a necessary one. He may use the colours in a thick paste, or slightly diluted, or as a thin wash ; they are diluted with a quantity of oil, or turpentine, or a mixture of the two. It may be explained that the thin wash or glaze is composed of a transparent colour for choice, very much diluted, and its purpose is to heighten the value or activity of a tone which has already been laid on and has dried. Delicate effects and fine harmonies may be obtained in this way. The colours which are in practice used for this purpose are as a rule transparent yellows (Indian yellow, yellow lake, raw sienna and sometimes dark cadmium), nearly all the reds, but principally the lakes, black, nearly all the browns, and particularly bitumen. Although they have immense advantages, glazes have the defect of being liable to damage by the hand of time. They are slow in drying, and there is a risk that they may become in corporated in the varnish if the latter is applied too soon ; and it must be admitted as an axiom that a picture will sooner or later have to be devarnished, and the painting itself should not be liable to injury when this happens.
A great number of prepared colours are now available ; and while it is not necessary to give a list of them, it may be of use to mention a small number of specially durable colours with which a great variety of effects may be obtained. These are : flake
white, golden ochre, strontian yellow, deep cadmium yellow, Venetian red, burnt sienna, cadmium red or vermilion, dark madder lake, ultramarine, cobalt blue, emerald green and ivory black or blue black.
This palette is only given as an example, since it would be arbi trary and useless to attempt to establish a uniform palette suit able to all temperaments. Some colours, too, may in themselves be injurious, and should be avoided as far as possible, but never theless may assist in creating the effect which is desired if they are used in the right place and with the necessary skill. For the nature of the colour itself is not the only factor; the manner in which it is used matters perhaps even more.
are two kinds in general use, very different from one another; those made of sable hairs and those made of hogs' bristles. The latter are the most generally used. They con sist of a metal collar which is generally flattened and keeps flat the bundle of bristles which form the brush itself. (See BRUSH : in Art.) The change from the round brushes, which were used until the i9th century, to flat brushes is due to the almost uni versal desire of the modern school to paint in separate touches with a full brush. The shape of the brush undoubtedly affects the nature of the stroke; but though it is difficult to describe the subtle difference made by the use of a round or a flat brush, be cause everything depends on the hand which uses it, it is easy to distinguish between passages executed with a sable brush and those executed with a hogs' bristle brush. The sable brush is better where precision of detail is required. The touch can be impasted and yet smooth, where bristle would not follow the exact intention of the painter with the same docility. Sable brushes are best for painting small pictures on panels, and for compositions where emphasis on detail gives the work part of its character. On the other hand it would be difficult to paint a life size portrait or a large landscape with sable. The softness of the hairs would make it difficult to deal with a considerable quantity of paint, and the touch would be greasy and soft while a firm hogs' bristle brush would enable the painter to lay on a broad and vigorous surface.
Painters have at all times used their fingers and this use of the finger as a sort of flesh-and-blood trowel gave Courbet the idea of using the palette knife as a partial substitute for the brush. By using a flexible steel knife it is possible to obtain a vigorous touch and great variety of technique. It would of course be impossible to do any delicate drawing with the palette knife, but no instru ment can be compared with it for preserving the purity of tones which often leave the palette fresh but are impaired by the time they reach the canvas. The palette knife can be wiped clean with a rag after each stroke; it represents an absolutely clean means of transferring the paint from the palette to the canvas, while only too often the brush is insufficiently cleaned and contains traces of all sorts of other colours. This does not however mean that the palette knife can take the place of the brush. The knife can only be used for certain restricted purposes, and for general use nothing can replace the brush. But everyone knows how important clean liness is in the composition of colours, and it is only too often for gotten that the palette, the vessel which contains the vehicle, and the brushes, need careful attention because they are the last recipients of the colours, and colours cannot be beautiful unless they are skilfully used.