Retouching varnish is much thinner than final coat varnishes. It can be used to bring back the paint quality of dull or dry oil. It is also used as a preliminary varnish as soon as the oil paint is dry, since oil paint can continue to dry through the film. This maybe useful for initial varnishing before an exhibition. Retouching varnish can be removed with white spirit prior to final varnishing or it can be left underneath.