Goma de éster

A modified natural resin made from rosin that has been esterified by heating with a polyhydric alcohol, such as glycerol. Ester gum contains the glyceryl, methyl, and ethyl esters of rosin acids. Ester gum is lighter in color than rosin and have a higher softening point but lower acid number. It is not used in artist paints or varnishes although they have been tried for wax-resin linings. It is used instead of copal, dammar, or kauri in making enamels, paints, nitrocellulose lacquers, and tung oil mixtures.