The nature of your craftsmanship will determine whether you obtain individual mixed tints and delicate fusions by rubbing with your fingers or with a stump, or whether you prefer to shade the colors lightly into one another by hand.
The second of these methods is the best way to steer clear of an effect of meretricious sweetness. As with drawing in chalk or with a lead pencil, so with the pastel: beginners are all too ready to stump and smear their work, delighting in the delicate way the colors run into each other, and not realizing what a sugary mess they are producing.
The discipline entailed in shading in, however, would speedily bring about a notable improvement. Only the artist in command of his materials will be sure of enhancing his effects by blurring his lines. With this in view, study the pastel paintings of the rococo.
We have already noted that pastels must be kept framed behind glass if they are to be hung on the wall. Unfixed pastels must also be treated in this way, since in a portfolio, for example, they will leave marks even on the smoothest interleaf. The glass must not be in direct contact with the painting. A simple way to prevent this is to give the pastel a mat cut to a suitable thickness.
There is a danger, however, that when the glass is polished on the outside with a woolen or silk rag, the color particles will be drawn to the inside of the glass by electromagnetic action. This is a frequent phenomenon with the modern pastel, but rare in old ones.
Possibly this may be due to the use of flake white (white lead) as the white pigment in old works, and the fact that its use is no longer allowed in pastel chalks sold commercially. Surely a somewhat exaggerated precaution? For even if white lead is poisonous, who is likely to breathe it in fatal amounts? It would not be at all easy to kill oneself with it; and anyone who wanted to could find surer methods. At all events we have in titanium white (RN 56) a wholly innocuous substitute for flake white.
The pastel medium has latterly branched out, chiefly under the stimulus of W. Ostwald, to bring mural painting within its range. A painting of this kind bears no comparison with a small-scale pastel, but with a pastel mural this is not the point. The point is rather that the use of pastels on the wall is straightforward and makes for an effect which is aesthetically most in keeping with modern notions of wall painting. This prompts us to the following reflection: a mural should not resemble a picture stuck on or cut into the wall, as they all used to; instead it should liven up a plain wall without attempting to disguise it. The wall must still be an integral part of the architecture.
Figures and similar objects should be apposed directly on the wall and not be separated from it, as formerly, by anything in the nature of a background or a frame. A brief glance in passing cannot take in the background graduations. Yet on closer study, they create an illusion of depth and breadth, an impression that the background suddenly recedes; and this can be all the more delightful if no attempt has been made to indicate perspective.
A moment later the design appears to return to the surface. The total effect is strengthened by the roughness of the plaster. Naturally, it does not lend itself to the application of a close, opaque color; the use of porous colors, however, causes the texture and shade of the plaster surface to extend to the whole design and underlines the nature of the wall surface.
We can, of course, make pastel completely opaque, by stumping or brushing in the color, for example. But this is wrong and, indeed, does violence to the material-just as it does to lay on porous colors with a half-dry brush. Obviously, pastel murals must be extremely thoroughly fixed. Shellac solution is not really suitable. However, the binding agents used for liquid wall painting, foremost among them casein solutions and waterglass, are well worth considering.
Nonreversible glue solutions can also be used indoors, though they must be given a dressing of formalin, and protected against the effects of humidity. A further prerequisite for the stability of a pastel on the wall is the right type of plaster. It must be thoroughly dried out, and care must be taken, when tinting the surface all over, to use only a binder which will suit the fixative to be used later.
The artist who wishes to execute a painstaking mural will accordingly prepare his own primer on fresco dry plaster not treated in any other way. Where casein is used as a fixative, priming is best carried out with the weakest possible casein bound color. This need not dry indelibly instantly, since a further casein solution will be sprayed on later. Hand sprays rather like air sprays are sold for this purpose. Immediately after use they must be thoroughly washed out in water. The safest way to test indelibility and make sure that not too much glue is used is to tryout the same plaster on a piece of board. For casein pastels, bought pastel chalks will do.