Whatever the material used in painting, it always consists of associating a colorful dust, called pigment, with an agglutinant liquid that we will call a binder. It allows us to carry the pigment and place it in its place, in a word to handle it. After drying, it provides cohesion and, depending on its nature, acts by refraction on the depth and sound of cough. This makes us think of music: the color of each pigment corresponds to a note of a certain height. But the special way to "sing" with these pigments or with these notes, the feeling we can expect, depend, for the painter, on the binder it uses, as, for the musician they depend on the instrument. Guasa, watercolor, fresco, oil use the same pigments, but differ in binder. Each binder has its own possibilities and limits just like flute, piano, violin or organ.
The artist will know how to choose with more safety if he knows the possibilities and limits of different binders, limits that cannot be forced without the work suffering. The artist will also know how to increase the richness of expression by a return to the old procedures, given recklessly, as with the help of modern discoveries. The binder consists of a product capable of solidifying at drying (glue, gum, resin, tiv oil), fluidized by a volatile fluid (usually water or an essence). It is known that the water is endowed with a very high capillary tension, much superior to that of the oil. Ziloty, talking about the action of this phenomenon in painting, compares it to that of an elastic film that covers the liquid and manifests the tendency to compress it. This is where the difficulty appears to get in watercolor an equal tone on a large surface, if the background is not already wet. If it is dry, it is known to interrupt the net and "rough" of a color color to the exact limits of the brush, the difficulty of resuming or combining two tones; This is why it is necessary to use "softening agents" to reduce this tension, such as ox iron, garlic juice and onion and alcohol.
This difficulty of the model caused the primitives who worked in tempera to treat the shadows with more or less frequent hashs. Very viscous, animal oils, basic material of the old tempera works and theater decorations, must be very diluted with water to allow the color to be applied. For this reason, when drying there is a decrease in tone because the pigment is not completely "dressed" (covered by the binder film). Guasa calls for gums (Arabica or dextrina), which forms richer solutions, remaining fluid. The tones decrease by mining less; Unfortunately, they remain all terne, without shine, and water sensitivity makes overlays difficult. Watercolor, which uses quite similar materials, differs from the Gasa through its lavium and non-treatment process. It highlights the white of the support that acts everywhere reflecting through a thin layer, soon more colorful than pigmented.
Its beauty is due to this bright transparency. Instrument of spontaneity and decision, it does not tolerate exaggerated load and corrections. Able to unite water with oil or other substances, the emulsions have played a significant role (tempera) in the past. Forgotten then, they offer the artist today, due to the discoveries in the field of chemistry, countless possibilities. But we will talk more about them. Let us note here only that, allowing immediate overlays, with them can be performed very quickly with great freshness. The presence of water reduces, because the fineness of the models, as well as the painting time.
Contrary to water, the oil, used alone, allows the thought, the slow elaboration of the models and the refinement of the crossings (passages); Instead, because it diffuses, it tends to stretch through its poor hair tension and the writing is no longer net. This is why the primitives, who already knew the possibilities of rubbing their pigments with the oil, preferred to paint with water, all the more so, as Theophilus recalls, they knew they could not overlap the colors without waiting for long periods. ' But in old techniques, we meet permanently overlaps. As Pierre Paula explains, the execution was simple; The local tone was first applied in thin and opaque flattening, then it was sufficient to return to this still fresh and absorbent fund, putting the lights and umbrellas; This is why he summarizes the history of the technique of painting saying that the old people made its color "singing" by overlap, and the modern by juxtaposition. Was this change want? Indeed, there were the discoveries of Goethe and Chevre, whose result was pantantism. But, as Emile Sabouraud observes, the possibilities offered by the two procedures could have been reconciled.
In fact, it was a replacement solution: the disappearance of the methods used. Theophilus (Schedular Diversarum Arlium) said: "Take the colors you want to use, rubbed them. Carefully in the oil, without water, and make the color mixture for characters and clothing as you have done so far; and you will paint. In their natural colors, as you will want, the animals, the birds and the foliage. But theophilus adds a little further: "Every time you want to put a color, you can not overlap another until the first one has been used, which For portraits, it is too lion and too boring. In this case it is preferable to use cherry resin. And after Van Eyck, bringing out the oil painting to what had been in Theophile's time, did the material that did not allow a rapid overlap to agree to these modern, eager to keep the freshness of an emotion? In order for the creative sensation or idea to be expressed without delay, not being able to overlap, they have juxtapus.
* Note:Havel, Marc -The technique of the painting, Meridiane Publishing House, 1980