A geometry compression method for sort middle, screen space, graphics of the standard graphics pipeline. The oil is contained in a reservoir remote from the heat source and the device comprises means for transferring the oil from a reservoir to a surface of a heat-absorbing means wherein heat from the heat source is transferred by conduction to said surface to volatilise the oil. The paddle exhibits excellent deflection and strength characteristics. A thickness of from 1-3 mm in our tests accommodated this space limitation.