Gouache to acrylic or oil paints in that it is normally used in an opaque painting style and it can form a superficial layer. Many manufacturers of watercolor paints also produce gouache and the two can easily be used together. Gouache paint is similar to watercolor, however modified to make it opaque. Just as in watercolor, the binding agent has traditionally been 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
Gum arabic solution in hot water (typically 10–25 g/litre), and then added to the glaze solution after any ball milling in concentrations from 0.02% to 3% of gum arabic to the dry weight of the glaze. On firing, the gum burns out at a low temperature, leaving no residues in the glaze. More recently, particularly in commercial manufacturing, gum arabic is often replaced by more refined and consistent alternatives, such as carboxymethyl cellulose (CMC). The historical photography process of gum bichromate photography uses gum arabic mixed with ammonium or potassium dichromate and pigment to create a coloured photographic emulsion that becomes relatively