Yellowing dammar

Dammar resin [dam(in)ar]. Pale yellow, transparent drop-like or irregularly shaped pieces of resin with a we ly aromatic odor from the south east Asian pitch tree (Shorea wiesneri, Dipterocarpaceae) and other Shorea or Hopea species. D. has varying hardnesses depending on its origin. 

It is a colorless to straw-yellow, oily liquid with a peppermint-like odor. It will darken and form a solid residue an exposure arxl aging. It is miscible with most organic liquids and it is a good solvent for such substances os nitrocellulose, ethylcellulose, law-viscosity cellulose acetate, polyvinyl chloride, vinyl resins, hydrocarbons, raw linseed oil, kauri gum, rosin, ester gum and synthetic rubber. It will only partly dissolve shellac and dewaxed dammar. 

On ageing, dammar polymerizes and some parts even become cross-linked, yellow and insoluble (Boon and van der Doelen, 1999). Dissolving coatings with solvents will therefore leave coloured insoluble material on the surface. For this reason, a mechanical method of removal should also be considered when the application and reversal of a dammar coating are being proposed. 

Lafontaine, R. H. (1979). Decreasing the yellowing rate of dammar varnish using antioxidants. Studies in Conservation, 24, 14-22. 

Dammar (Damar) da-mor n [Malay] (1698) Natural resinous exudation from trees of the Dipterocarpaceae family, which grow chiefly in the East Indies (now Indonesia) and Malaya. Very pale in color (practically colorless to deep yellow). Soluble in hydrocarbons without the necessity of running. Average acid value of 30. A fossil resin used as an ingredient in printing ink varnishes. 

---