Removability dammar

A varnish is often appHed on top of the paint layers. A varnish serves two purposes as a protective coating and also for an optical effect that enriches the colors of the painting. A traditional varnish consists of a natural plant resin dissolved or fused in a Hquid for appHcation to the surface (see Resins, natural). There are two types of varnish resins hard ones, the most important of which is copal, and soft ones, notably dammar and mastic. The hard resins are fossil, and to convert these to a fluid state, they are fused in oil at high temperature. The soft resins dissolve in organic solvents, eg, turpentine. The natural resin varnishes discolor over time and also become less soluble, making removal in case of failure more difficult (see Paint and FINNISH removers). Thus the use of more stable synthetic resins, such as certain methacrylates and cycHc ketone resins, has become quite common, especially in conservation practice. 

Dewaxing n. Process of removing waxes from natural resins (dammars, shellacs, etc.). 

Resene, J n. Dammar is a mixture, and one of its constituents is resene, sometimes known as dammar wax. It is this material which is removed in the so-called dewaxing process, which is an essential operation to make the dammar suitable for use in nitrocellulose lacquers. 

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. 

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