There are three major considerations in selection of a varnish for a painting: 1. the varnish will protect and seal the paint film, 2. sometimes paintings dry with dull or matte areas due to the use of turpentine--varnish helps equalize the gloss, and 3. depending upon how much varnish resin used, the painting will appear the same as wet--in this case varnish will also help equalize gloss and protect. Natural resins are products of certain trees, whereas, synthetic resins are the products of chemical manufacture. Natural resins are; damar and copal. Synthetic base resins are known by the following names: Elvacite 2044 (DuPont), Acryloid F-10 (Rohm and Haas), Acryloid B 67 MT (Rohm and Haas), Acryloid B 67 MT (Rohm and Haas), and Acryloid B 72 (Rohm and Haas). Solvent is added producing a varnish which is marketed under various trade names, the most common being: Weber's Synvar and Univar, Winsor & Newton's Winton Picture Varnish, Bocour Artist Colors' Magna Varnish, Grumbacher's Crystal Clear Varnish, Krylon's Crystal Clear Spray, and Permanent Pigment's Soluvar Varnish. Synthetic varnishes discolor less, remain flexible, and remain soluble longer than natural resins. The artist is the best judge of the type of varnish to be used for a painting. Varnish may be brushed or sprayed.