A wash is a term for a visual arts technique resulting in a semi-transparent layer of colour. A wash of diluted ink or watercolor paint applied in combination with drawing is called pen and wash, wash drawing, or ink and wash. Normally only one or two colours of wash are used; if more colours are used the result is likely to be classified as a full watercolor painting. The classic East Asian tradition of ink wash painting uses black ink in various levels of dilution. Historically associated with the four arts of the scholar-officials, the technique was often applied to landscapes in traditional Chinese, Japanese, and Korean painting. Source: Wikipedia (en)