A traditional 19th century painting medium prepared especially for hobbyists and decorative painters (i.e. tole painters), Grumbacher Copal Painting Medium is made with a modern synthetic copal resin, and has all of the manipulative and drying characteristics of the original 19th century preparation. When added to oil colors, Copal Painting Medium improves flow, accelerates drying, and imparts hardness and a high gloss to the dry paint film. Because this product may cause yellowing and darkening of the colors with time, its use is recommended for occasional or impermanent painting only. Dilute Copal Painting Medium with Pure Gum Spirits of Turpentine or Grumtine only.