Join Date: May 2016
Location: Stockholm, Sweden
There is no reason to varnish oil paintings at all. In earlier times, the air was so full of contaminants, and the paintings so valuable, that they saw it necessary. But varnish only degrades paintings. You've already discovered the degradable effect. Unvarnished oil paintings can be cleaned with soap water. The oil paint layer is very sturdy and repels dirt. Georges Braque was appalled when he saw the effect of the conservators' work on some of his paintings. They had mistakenly varnished them, despite the fact that he never used varnish.