Gouache is a French term used to describe a type of watercolour paint. The word is derived from the Italian guazzo which literally means a watering place. Before the 19th century the term guazzo was applied to glue-size painting.
Gouache is opaque. The pigments used are ground in water and mixed with gum. The results of using gouache appear quite different from those achieved with washes of watercolour, the look of which is more dependent on the nature of the paper beneath.