Quick Overview
Shellac is a natural resin that is deposited by the female lac insect on the branches of trees in India and Thailand. It is soluble with alcohol, but not with mineral spirits or turpentine. It forms a tough yet flexible film, with many applications. It is suitable as a top coat for gilding when applied thinly, a sealant for porous surfaces, an isolating layer for tempera paintings, a base for pigmented inks, a protective layer for collograph plates, and a warm varnish for wooden floors and furniture. As it is prone to darkening with age, it is not recommended as a varnish for oils, and its solubility can reduce over time.
There are various grades of shellac. When mixed with alcohol, it may initially form a cloudy mixture, due to traces of wax in the shellac, but this should become clear once it has dried. The highest grades of shellac are Clear Dewaxed Shellac, which has been de-coloured using the carbon filtering method, Lemon Shellac, and Orange Shellac, which are pale in colour. Button Shellac is less refined and therefore produces a reddish varnish. It was, in fact, widely used as a red dye before synthetic dyes became available.
