Color changes in prepared samples of grounds based on those used by Vincent van Gogh were measured before and after varnishing with dammar and artificial aging. Sections of the samples were lined using wax-resin. Varnish was removed using solvents, and practical observations were made about the influence of the ground composition and lining on the reversibility of varnish. Quantitative measurements of color change and qualitative observations made during varnish removal showed that wax-resin lining facilitated varnish removal, whereas varnishing of absorbent grounds was irreversible. Consultations with conservators and treatment reports of paintings cleaned at the Van Gogh Museum, Amsterdam, provided some theoretical context and practical guidelines for the removal of nonoriginal varnishes from Impressionist paintings.