Archival Copal Medium Prepared from synthetic and natural resins and refined turpentine, Archival Copal Painting Medium is excellent for glazing, thin or impasto painting, and wet-on-wet techniques. May be thinned with turpenoid® or turpentine.Archival Copal Medium Prepared from synthetic and natural resins and refined turpentine, Archival Copal Painting Medium is excellent for glazing, thin or impasto painting, and wet-on-wet techniques. May be thinned with turpenoid® or turpentine.Archival Copal Medium Prepared from synthetic and natural resins and refined turpentine, Archival Copal Painting Medium is excellent for glazing, thin or impasto painting, and wet-on-wet techniques. May be thinned with turpenoid® or turpentine.Archival Copal Medium Prepared from synthetic and natural resins and refined turpentine, Archival Copal Painting Medium is excellent for glazing, thin or impasto painting, and wet-on-wet techniques. May be thinned with turpenoid® or turpentine.