Gouache

The color of the paper usually has little effect on gouache paint as an underlayer, and so sometimes a tinted paper is used for special effects, the exposed areas of the paper being utilized as a part of the color scheme of the painting. Transparent watercolor is occasionally combined in a gouache painting; as a general rule this produces a better effect than when gouache is used in a picture that is predominantly watercolor. Some painters achieve a full range of textural and color effects by combining watercolor, gouache, and pastel in the same picture. Gouache colors have a certain robust solidity which gives the effect of an impasto paint layer, heavier than that which actually exists and, therefore, the paint need not be piled up thickly. Because gouache paint is a real, continuous film with a not-too-flexible gum adhesive, it is likely to crack or peel off if applied too heavily.

A great variety of aqueous paints has been employed by artists [p. 152] to produce pictures popularly accepted as gouache paintings--for example, cheap poster colors, casein paints, tempera paints, watercolors mixed with Chinese white. True gouache paints, however, capable of being handled to give the best results in that technique, are made especially for the purpose, from the same gum solution and other materials used for watercolors.

The lines of artists' tube colors called "designers' colors," however, are usually good-quality materials and may be used as gouache colors with certain restrictions. Being intended for use by designers, illustrators, and commercial artists, these lines often contain superbright pigments that are not lightfast, for the artists who work at those tasks are not concerned with permanence. One must therefore be careful to pick out the permanent pigments as listed in this book--the ochres, the umbers, the ultramarines--and avoid the geranium reds, the peacock blues, and others with nonstandard names [see page 33 - Pigments/The Permanent Palette].

Unlike the transparent watercolors, gouache paints may be easily and profitably made at home.

A typical watercolor and gouache binder is made by adding to a 1:2 solution of powdered gum arabic about 1/3 its volume each of glycerin and honey-water [1:1], a little wetting agent, and a very small amount of preservative [page 162 - Aqueous Paints/Preservatives and Odorants]. Some gouache colors are improved-to a grater extent than are transparent watercolors--if the vehicle in which they are ground contains a pasty adhesive in addition to the gum-arabic binder. A stiff solution of white dextrin [p. 154] added to the gum solution will overcome the stick or stringy consistency which is an occasional defect in some aqueous paints. The amount may be varied according to the requirements of each particular pigment; the result will generally be a smoother, more easily brushable paint. It is generally said, however, that for the finest and most sensitive professional use the gum content should remain the principal ingredient in homemade gouache; the more dextrin used, the more the paint will tend toward the less delicate and less permanent poster-color type of paint.

Inert pigments, such as blanc fixe or chalk, are often ground in with some of the colored pigments, not as adulterants but in order to increase their bulk and to improve their brightness or opacity. Those colors which are ordinarily transparent in oil and watercolor act as body-colors in gouache, and often yield somewhat different color effects. [pp. 152-154]