Gouaches

Gouache (/ɡuːˈɑːʃ, ɡwɑːʃ/; French: [ɡwaʃ]), body color, opaque watercolor, or guache, is one type of watermedia, paint consisting of pigment, water, a binding agent (usually dextrin or gum arabic), and sometimes additional inert material. Gouache is designed to be used with opaque methods of painting. The term, derived from the Italian guazzo, also refers to paintings using this opaque method.

Gouache has a considerable history going back over 600 years. It is similar to watercolor because it can be rewet and the paint can become infused with its paper support. It can also form a superficial layer like acrylic or oil paint. Also like watercolor, gouache dries to a matte finish. It is similar to acrylic or oil paints in that it is normally used in an opaque painting style. Many manufacturers of watercolor paints also produce gouache and the two can easily be used together.

Gouache paint is similar to watercolor modified to make it opaque. Just as in watercolor, a binding agent is present. This was traditionally gum arabic but since the late nineteenth century cheaper varieties use yellow dextrin. When the paint is sold as a paste, e.g. in tubes, the dextrin has usually been mixed with an equal volume of water. To improve the adhesive and hygroscopic qualities of the paint, as well as the flexibility of the rather brittle paint layer after drying, often propylene glycol is added. Gouache differs from watercolor in that the particles are typically larger, the ratio of pigment to binder is much higher, and an additional white filler such as chalk, a "body", may be part of the paint. This makes gouache heavier and more opaque, with greater reflective qualities.

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