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 "Acacia seyal", the species more prevalent in East Africa, is collected from naturally occurring exudations on the bark. Traditionally harvested by seminomadic desert pastoralists in the course of their transhumance cycle, acacia gum remains a main export of several African nations, including Mauritania, Niger, Chad, and Sudan. The hardened exudations are collected in the middle of the rainy season (harvesting usually begins in July), and exported at the start of the dry season (November). Total world gum arabic exports are today (2008) estimated at 60,000 tonnes, having recovered from 1987–1989 and 2003–2005 crises caused by the destruction of trees by