Over at Painting Perceptions there’s a great post on the historical symbolism of varnishing paintings.
It covers a fair bit of ground, but for me the major takeaway was that, back in the 19th century, not varnishing their paintings was one of the ways the Moderns distanced themselves from their more aesthetically conservative Academic counterparts. Varnish, over and above its practical function as a protective layer, carried a whole freight of symbolic value, the sum total of which was to affirm a painting’s status as a Valuable Object, part of a continuity of great art extending back over the centuries. The Moderns, beginning with the Impressionists, sought to make painting that was less obviously precious and more an expression of the contemporary world with its rough edges and discontinuities.
Anyway, I’ve been thinking about this for a while now, mainly because I’ve started painting oils again and I have to figure out what my approach to varnishing them (or not) is going to be. Symbolism aside, varnishing your paintings isn’t a bad idea. Varnish may carry some unwanted symbolic freight, but it also confers a significant practical benefit: all else being equal, your paintings last longer and are easier to clean and cheaper to maintain. So there are good, pragmatic reasons for varnishing.