Certain pigments when combined with an oil or oil and resin medium form transparent or translucent paint films or glazes.
When applied over another colour, generally lighter in tone, they modify that colour but being transparent do not obscure it. By varying the thickness of the glaze, tonal variation and an illusion of relief can be obtained.
The term glaze is sometimes used to describe any thinly applied and therefore translucent paint layer. However, if the thin paint layer is lighter than the underlying colour it is more properly called a scumble.