The first step is the small-scale sketch, followed by individual studies such as whole figures, heads, hands, and drapery. Next the sketch proper. This may be on the same reduced scale as the first sketches, or somewhat larger, or very occasionally, even at this stage, full size.
As a rule, glue colors will be used on white cardboard paper. At this point the cartoon known as the "tracing" is drawn, a full-size sketch of the most important outlines, which is pressed into the wet plaster. This cartoon obviously must be made on soft paper only. The outlines are marked through with a blunt metal graver or any other suitable tool. It is also .possible to perforate the outlines, and then to trace them Qnto the wall by filtering pigment through a bag of powder.
Any falling particles will be held by the plaster, so this method cannot always be used. Moreover, you may wish to use pigments which would be destroyed by the lime, thus disappearing after a time, such as the cadmium and alizarin colors and cyanide blue.
A colorless outline lightly pressed into the plaster will not be inconvenient when painting, and it leaves the artist free to work. Fresco painting is carried out on the same principle as watercolors, that is, proceeding from light to dark. Glazing is likewise used without adding white pigment.
In monumental works, however, these principles are followed less strictly. It may be necessary to mix in some white pigment, and if so, white lime is the only sort to use. There is little use-rer black, but if it is used, carbon should be avoided. Even though the lime does not destroy the carbon, it binds it only temporarily; in the end it decays together with a thin surface layer of plaster. Manganese black is better.
As with all monumental painting, simple and largescale use of color is alone appropriate and impressive. This accounts for a fundamental difference between fresco and other media as regards planning the picture; we must also remember that relatively little correction is possible while work is in progress. The ideal is to do all the painting at a stretch, for too much over-painting interferes with the process of binding the colors to the ground.
The color is best applied with a sort of soft round watercolor bristle brush of gigantic proportions. The brush should not be too stiff, as it would tear away the soft surface layer of mortar. Hair brushes would be too quickly spoiled by the lime. Once the fresco is finished, no further treatment is called for. On the contrary, to overpaint it or varnish it in any way would utterly nullify the special effect of a fresco painting, which is of exceptional beauty. As a painting medium in the truest sense, it does not belong on the face of a building, but in a large room. Only there is there a guarantee that the fresco will suffer as little as possible from attack by acids in the air.
For an external wall face, the only satisfactory method is to paint with waterglass, known also as silica or mineral painting. Once the technical process of binding has been fully dealt with, there remains little to be said about the actual method of painting. As it is hardly possible to make one's own materials, a description of these processes must read rather like an abstract from the printed instructions of the manufacturer. The colors are thinned with water or waterglass and applied with a fresco brush to dry plaster previously scraped; or alternatively they may be laid on in crayon form, like pastel chalks.
All the pigments must be tempered with zinc and magnesia. The binder, waterglass, is usually sprayed on after the picture is painted, or it can be used as an intermediate fixative where a heavier application of paint is desired. That is all. The build-up of the picture depends on whether you use a dark-tinted plaster, a special facing plaster which is colored in a block, or a light-colored plaster. This determines whether the picture is built up like a watercolor, an oil painting, or a pastel.
Compared with the marked individuality of other media, the total impression is not very striking. To quote from Wilhelm Busch, we might say that it is nicely colored, and therefore good. This criticism is not merely derogatory. The outstanding durability of silica paint assures for it a future of great promise and leads us to suppose that some great artist will use it to achieve effects never before thought of; especially as it is not absolutely essential to have a plaster wall surface underneath. The manufacturers of silica paint also sell primers which can be applied on any support to give a good enough hold, and these make a
satisfactory foundation for silica colors. On a ground of this type you will be able to experiment in your studio.
When you come to reflect on everything that has been said about the most important painting techniques, you will see that all techniques are good when they are properly handled and all are bad if you make mistakes. None is perfect. Your choice must depend as much on your personal inclination as on the use you intend to make of your work. Any artistic experience can be transposed into any medium; though it is a fact that some seem to call for one kind of medium and others for another. Thus, it is most revealing, particularly for a beginner, occasionally to carry out the same motif in a variety of media. It is dauntless zeal which will achieve the goal, and not irresolute musing.