Painting made with a pigment ground in gum, usually gum arabic, and applied with brush and water to a surface, usually paper. The pigment is ordinarily transparent but can be made opaque by mixing with a whiting to produce gouache. Transparent watercolour allows for freshness and luminosity. Whereas oil paintings achieve their effects by a building up of colour, watercolours rely on what is left out, with empty, unpainted spaces being an integral part of the work.

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