Varnish

Varnish is used on top of oil or acrylic paintings, in the former case to help prevent the oils yellowing, and in both cases to a different sheen (matte or glossy) to the finished painting. Varnish on a painting that will not be under glass also protects it from damage by dirt, dust, and pollution.

Putting varnish on a painting is not something that can be rushed. The paint must be completely dry. For an oil painting that can take several to six months depending on the paint.