O

Oil paint is form of a slow-drying paint that consists of particles of pigment suspended in a drying oil that forms a tough, coloured film on exposure to air

The term opaque originated from the Latin, meaning 'dark' meaning 'not transparent' and opaque substance does not let any light pass through at all. A paint that is opaque will give a solid colour.

Op art, short for optical art, is a style of visual art that uses optical illusions. Op art works are abstract, with many better known pieces created in black and white. Typically, they give the viewer the impression of movement, hidden images, flashing and vibrating patterns, or of swelling or warping.