glaze

glaze. A transparent or semi-transparent layer of paint applied over another layer so as to modify its colour; the light passing through is reflected back by the under surface and altered by the glaze. The effect produced by glazing differs from any obtainable by directly mixing colours together, for the technique imparts a special depth and luminosity. From the 15th to the 19th century most oil paintings were built up as an elaborate structure of superimposed layers, glazes, and scumbles over an underpainting, but since alla prima painting became the norm such a highly deliberate, craftsmanly approach has fallen into disfavour.