Gouache (pronounced "goo-WASH") comes from the Italian aguazzo word for "mud."
Gouache is considered to be a watercolor paint. But unlike traditional watercolors that are translucent and transparent, gouache has clay in it. This makes the paint opaque. As a result, purists disagree as to the different definitions of what gouache is or how it should be used.
Gouache first appears in the decorative and pictorial embellishments in medieval illuminated manuscripts. The earliest modern examples are nature paintings by the 16th century German artist Albrecht Dürer, and in a series of paintings by Gaspard Dughet. It reached a high point in the 18th century, particularly in France, in decorative works by the French painter François Boucher.
Gouache was probably introduced to England by painters with French ancestry, such as Joseph Goupy, who was drawing master to the family of George I. From around 1740, English topographical artists used gouache frequently. By that time, gouache had begun to decline into purely decorative painting on fans, screens and theatrical scenery. The Swiss topographical artist Louis Ducros, working in Italy on large format gouache and watercolor paintings, continued almost alone to use the medium in fine art works. In the 1830's, the method was revived by several Victorian watercolor artists, who used it until the end of the century.
Mixing watercolor pigment with an opaque white pigment in a watercolor vehicle (made with gum arabic) is traditionally referred to as gouache. The method of mixing concentrated watercolor pigments with a vehicle that is made with fish gelatin (isinglass jelly) or animal gelatin (size) — without the addition of any white pigment — is traditionally called bodycolor. However, the two terms are sometimes confused or used interchangeably, both in historical writings and current usage. Some "designer's gouache" paints are made with concentrated pure pigment in a watercolor vehicle, without any added white pigment.
In any cases, gouache is an opaque watercolor paint. There are six characteristics that distinquish gouache from traditional transparent watercolors:
- Gouache is a much thicker paint, which does not affect the color. Unlike transparent watercolors, gouache can be painted on a white or tinted support, with little or no difference in the finished color appearance.
- Colors must be lightened by adding white, not by dilution to show more of the white paper, as in transparent watercolors.
- Gouache is not applied in glazes or tints (unlike oils and watercolors, where glazing one color over another is a common technique).
- Gouache is not absorbed into the paper but remains on the surface in a thick layer, allowing for limited textural effects created with brushstroke variations in the surface of the paint. However, it will crack when dry if laid on too thickly.
- Gouache creates flawless, flat color areas, which are more difficult to attain in watercolors. Because of the concentration of pigment and filler, blossoming or blooming effects are difficult to achieve.
- Gouache covers all painted layers below it. In transparent watercolors, a dark background must be carefully painted around the white flower in front of it, and painters normally work by laying darker colors on top of light. But in using gouache, backgrounds can be painted first, then the flower directly on top of it, and lighter colors can often be layered on top of dark.
These characteristics makes gouache popular with architectural or commercial artists. The flat colors photograph and reproduce very well, making gouache ideal for reproduction. Gouache does not undergo a chemical change when dry and therefore can be rewetted and reworked, just like watercolors. And the rapid drying times mean that a project can be completed relatively quickly.
Finished gouache paintings should matted and framed under UV shielding glass or plastic.