Glaze
A thin, transparent layer of paint laid over dry paint to deepen or shift its colour.
Also: glazing
In painting, a glaze is a see-through film of colour brushed over a dry layer. Light passes through it, bounces off the layer below and returns, giving a depth and glow that a single opaque mix cannot. Oil painters of the Renaissance built up rich reds and blues this way, over many days. In pottery the word means something else: a glassy coating melted onto clay in the kiln, which makes it waterproof and carries much of the colour of ceramics and tiles.