Dammar and Mastic Varnishes—Hardness, Brittleness, and Change in Weight upon Drying

THE National Gallery of Art, Washington, D.C., established a Fellowship at Mellon Institute in 1950 to investigate the possibility of developing modern materials to improve upon the traditional materials of the artist. As part of an investigation of picture varnishes, selected physical properties of dammar and mastic resins were studied in detail [I]. This paper presents experimental particulars of the investigation. The methods used and general conclusions have been revealed previously [2]. For picture varnishes, dammar resin, derived from the Dipterocarpaceae family of trees, is usually dissolved in petroleum or turpentine; mastic resin, from the tree Pistacia lentiscus, in turpentine. Solutions of the resins are generally prepared without heating. Not all of the components of the resins may be soluble in a given solvent at room temperature. For this reason, as well as for the possible effects of solvent, it is best to distinguish properties determined with the whole resins from those determined upon dried films laid down from solution. This paper is concerned with the latter. The immediate purpose of this investigation was not to evaluate these traditional materials