Why are paintings varnished?

Oil paintings are meant to be varnished for the same reason furniture is—to protect and enhance the surface. Perhaps because it was done quickly for a magazine this painting was never varnished. Therefore the surface became dirty and dull with age. The surface was carefully cleaned and a layer of transparent varnish was applied to saturate and enhance its beauty. Below you can see the contrast in the before (left) and after (right) cleaning images.