Water color is a brilliant and flexible medium. Jt has several practical advantages in that the equipment needed is small, compact and easily carried. A finished water color can be painted much more rapidly than an oil, and the nature of the technique lends itself well to quick sketching in the field.
In water-color paints the usual binding material for the pigment is gum. Gum arabic, the one most frequently used, is a product of the acacia tree and is soluble in water. Other water solubles such as gum tragacanth, dextrin, fish glue, and egg white are occasionally used. Glycerine and sugar of honey added to the medium in small amounts keep the color moist and in easily workable condition. They also act as plasticizers to prevent cracking of the paint film. Because the nature of the medium does not lock up the color as firmly as oil, only pigments of the most permanent structure should be used. Fugitive or chemically active pigments quickly fade or change color. In order, to prevent colors which have been mixed together from separating, the pigments in water color should be very finely ground. The task is difficult and it is not advisable for the artist to prepare his own water colors. Those prepared by manufacturers are sold in cakes, porcelain pans, or put up moist in tubes.
Although parchment or silk may be used, the commonest support for water color is paper. The paper should be very light in color or white; the ground on which water color is executed greatly affects the luminosity of the work. Paper made of linen is the best. It is strong, tough, and unchangeable in color. It takes water very well. Papers made of wood pulp are usually poorly sized, darken easily and become brittle. Color holds best on paper with a grained texture. In cases where the paper has been manufactured without sufficient glue in its structure, it is advisable to size the surface with a thin gelatin solution. Otherwise the paint may run.
Water-color paper should be kept flat. Any creases will make the washes appear uneven and pigments adhere poorly. The paper must be stationary. Tack loose sheets of paper to a drawing board, or mount them on a stretcher. The water-color paper blocks sold at art stores eliminate the trouble of mounting your paper. Some artists feel that the block paper has a tendency to bubble when wet, and prefer the stretching or mounting system.
The brush used is important in water-color work. The hairs of the brush should form a point which will not divide when used. The best brushes are made of sable. Flat-bristle brushes, broad-wash brushes and camel's-hair brushes are also used for many purposes. The most accurate palettes for water color are white enamelware. Water color always dries lighter than it appears when wet; this change of tone must be taken into consideration.
Pure water color is transparent. Washes of diluted color are placed on white paper to produce tints. Where a white tone or highlight is desired, the paper is left uncovered. Water-color paint may be laid on the paper in various ways. Large areas of flat tone are applied in washes with a large brush fully charged with water and color. Technical skill and practice are necessary in laying an even wash. While the wash is thoroughly wet the paper is tilted back and forth at an angle until the pigment settles out into solid spots. This gives granulated textures to the color surface.
Dark detail may be applied over a lighter wash, completely covering the color underneath. But the possibility of obscuring a dark tone by placing a lighter color over it is very limited. When this is required you may either remove the dark portion, or cover it with an opaque paint. Opaque color kills the translucence of water color and it is customary to remove or lighten the dark tone by the wet methods of "wiping out" and "sponging" or by the dry methods of "scratching out" and erasing. In "wiping out," the paint film to be removed is redissolved by flooding it with water; the color in the solution is drawn off by the application of blotting paper. The tone will be lighter after each wetting, and continued operations will leave the paper white. In "sponging" you go lightly over the paint film with a wet sponge. The sponge should be washed frequently during the process. "Scratching out" is the process of removing the color by scraping the surface of the paper with a knife. It is used mainly as a finishing touch, since it destroys the surface of the paper for further work in that area.
You can use water colors for highly finished work or for recording rather rapid impressions. A sketch in pencil, pen or crayon is usually executed on paper before any painting is done. The picture may then be built up in various ways. A series of very liquid washes may be used and superimposed on each other until the general local colors of the subject have been obtained. At this point, with paints less diluted, the details of form and shadows are introduced and carried as far as the artist desires. Very liquid effects are sometimes achieved by wetting the entire surface of the paper or a limited area before beginning to paint. This allows the colors to spread, running into one another. The opposite effect is obtained by painting on dry paper with very little water on the brush.
The method of painting with opaque water color is usually known as gouache. Commercial gouaches such as poster paint, are rendered opaque by the addition of white fillers of barites or clay. Much the same effect can be achieved by mixing water color paint with Chinese white, a tube color of zinc white ground in a gum medium. The appearance of gouache is somewhat that of pastel executed in a wet rather than a dry fashion. In gouache you are not limited to white or tinted grounds but may use extremely dark paper or cardboards. The opaque colors easily cover the dark ground which in some places may be left unpainted as one of the tones of the picture. Gouache is much lighter after it has dried.