The restorer's greatest problems concern the surface coating of the painting. A decayed or badly discolored varnish may be removed painstakingly by mechanical means or regelled with the judicious use of solvent, often applied as a delicate spray. In other cases the old varnish may be powdered by rubbing and removed by hand or, more commonly, chemically dissolved. Such techniques are beset by dangers inherent in the variable nature of the original pigments and varnish, and the risk of injury increases with the age of the painting. When a new varnish is applied, the contemporary restorer uses a much more easily removed surface protector than was common in the past.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.