Today, velvety "pastel paper" may be bought ready-made. However, only a master will succeed in using this type of paper without producing tawdry color effects. A further point is that these velvet-type papers are always tinted, but not always with light-fast colors. Thus, they are best recommended for use with completely opaque chalks.
The most sympathetic paper is a rough white, such as a first-class Ingres paper. To give it a tinted ground, rub it lightly downwards and across with a broad pastel chalk. Then, with a soft wad of cloth, merge the chalk strokes in an even, circular motion over the surface. However carefully you do this, some irregularities will still remain, almost a texture which has a lively charm similar to that of an imprimatura. As with the latter, you can begin with a drawing underneath, which must, of course, be fixed before the paper is tinted.
Fixatives tinge the colors with gray, particularly if fillers rather than pure white pigments are used in the composition of the crayons, as they are apt to darken in the binder. This is almost the rule with ready-made pastel colors. As a matter of fact, manufacturers often use coal tar for pastel colors, which are seldom if ever light-fast. After a time, the picture becomes progressively paler; only inorganic permanent pigments retain their effect. You can imagine how extraordinary a picture will look then.
Happily, the coal tar colors in use are partly soluble in alcohol. I say happily, because this enables you to make a test. On a sheet of thin paper, such as French Ingres, draw a line with each of your pastel colors, one beside the other, and then spray them with alcohol. The soluble colors will at once penetrate the paper and make runny blots on the reverse side. Unfortunately, this does not mean that. all the colors which do not go through will prove satisfactory. Certain coal tar colors are not soluble in alcohol, among them alizarin red (which is intrinsically satisfactory) and such dubious, impure pigments as chrome yellow, Cassell brown and cinnabar.
The graying of pastel paintings due to fixing can be obviated by the exclusive use of zinc white, flake white, and titanium white instead of chalk and analogous white pigments. But to be quite sure, you should make your own pastel colors. Only then will you be certain of working with worthwhile pigments.
You should set about preparing your pastel chalks more or less as follows: using a small trowel, knead your powdered pigment with water and a trace of tragacanth gum. This dough-like paste
should be left for a day or two with a damp cloth over it to allow the pigment to become saturated with water and gum.
When it has been left in this way, you will see whether to add more water or more pigment. When your mixture has reached the right consistency, take some pieces out and roll them on a tray to a uniform thickness. The crayons can then be placed on a baking sheet lined with parchment and placed in an oven. They should stay there on a low heat, with the oven door open, for a few hours.
To dry them in the air takes too long and gives the glue time to go mouldy. Unfortunately, the exact quantity of glue cannot be laid down; it is simply a matter of finding out for oneself. Just enough glue is needed to hold the crayons together, but several pigments cohere without glue at all, with nothing but water.
To obtain a mixed color or a tint lightened with white, you should proceed as follows: first make long, thick crayons of equal size out of the appropriate pure pigment and white (preferably titanium white), and keep them really moist. Next, cut one tenth of the length off the end of the colored crayon, and substitute a piece of the white crayon for it. Blend the two together, and you have a new crayon. This affords a clear-cut and reliable means of obtaining any mixed or whitened tint.
As each crayon dries, place a strip of thin parchment around it, with appropriate remarks. If you take the trouble to make crayons out of all the important pigments, say 20 of them, preparing each in its pure, mixed and whitened form, you will soon have a set of 100 or more crayons, which should last you quite a long time.
This gives you an intimate contact with your colors, and is a new and most rewarding experience which amply repays all your labor. Apart from this, a pastel painting is built up on the same principle as an alia prima oil painting. Thus, you proceed from medium tints to darker ones, with the cool colors predominating. Next, paint in the brighter and stronger colors, rendering the deepest and warmest shadows, and last of all the high lights.
This should be gone over lightly, not pressed or rubbed, and for this reason corrections should not be made to the lines, but whenever possible and needful it is better to erase the wrong lines with a soft rubber eraser and go over them again. However, supposing the wrong color adheres as a result of repeated fixing, all you can do is to prepare and fix a fresh white ground to receive clean, bright colors again. The colors will stand out best on a white ground.