The fourth sessions of the Trihue Watercolor class for Winter 2018 were held on Wednesday, February 7 and Sunday, February 25. We critiqued the edges and gradations homework assignments. Transparency illusions, in the form of films and veils, were the new topic for the week. Dick showed transparency illusions from Albers’ Interaction of Color, pointing out ones that succeed, and some that fail because they are inconsistent with the actual phenomenon. Painting film illusions in watercolor is easy; painting veil illusions requires a painting strategy.