Talens Retouching varnish

Retouch or intermediate varnish can be used to brighten areas of an unfinished oil painting that have become dull (which can occur if the oil in the paint absorbs into the underlying layers). Apply a thin layer of retouch varnish to the dull area when the paint is touch-dry, and allow it to dry until the varnish is also touch-dry. After this, painting can continue on top of the intermediate varnish.

Intermediate varnish can also be used as a protective, temporary isolation coat when the work is not yet fully dry. Apply it as a thin layer – a too thick layer may potentially soften the underlying paint layer. However, a thin layer of intermediate varnish does not prevent the paint from fully drying; it simply slows down the drying process. The intermediate varnish can later be removed (using mineral spirits or balsam turpentine) or a final picture varnish can be applied over it as desired.