Glossary: Varnish

Not all artist's varnish their paintings, but in general it is of great advantage to do so. First of all it protects the painting against dirt that can get into the paint and make cleaning very difficult. Secondly, it has the effect of giving the painting greater depth and contrast. It also removes bloom which appears on the surface of older paintings. There are many grades of varnish from light retouch to heavy copal. The first is clear and delicate, the later very yellow in colour and thick.