When a painting becomes dark and discolored, it should be cleaned and restored by an experienced art conservator rather than attempting to do-it-yourself. There are many home remedies that have been tried and published in magazines and trade journals to clean paintings. Some of our favorites are; “the raw potato”, rolled bread dipped in red wine, household spray cleaners, dish soap, linseed oil, furniture polish, fingernail polish remover (acetone), lighter fluid, and cooking oil. Unfortunately, these materials can cause irreversible damage to the surface and structure of a painting, and should not be used under any circumstances. Many simply coat the surface of the painting with a layer of slime that appears to temporarily wet or clear the image. This application eventually dries, discolors and further obscures the image. Other home remedies can permanently dissolve and wipe away portions of the paint. Covering a painting with layers of linseed or cooking oil will accelerate the deterioration of the canvas support.
Cleaning is one of the most challenging areas of painting conservation, and requires specialized skills, materials and experience. The painted surface can easily be damaged by untrained hands. Cleaning and varnish removal are procedures that require a thorough understanding of art, art history, chemistry, and materials science. One must have an understanding of the materials included in each layer of a painting’s structure and how they may be affected by the application of cleaning agents and solvents.
Damage from improper cleaning methods and materials may not be immediately apparent. For example, improper cleaning can weaken the bond between the paint, ground, and support layers resulting in paint loss over time. The use of water during cleaning may swell and shrink the canvas fibers, causing unnecessary tension on the paint and eventual cracking and flaking.
Paintings are typically cleaned in stages by an experienced art restorer or conservator. Preliminary tests are carried out to determine the effectiveness of cleaning agents and the solubility of the varnish and paint layers. Many different materials and/or combinations of materials may be needed to safely clean a painting. A material or solvent that is used to remove surface dirt and grime, may not effectively reduce or reverse the discolored varnish.
Cleaning agents may also react to different colors and pigments used throughout the painting. Some colors and layers are far more sensitive than others. There are paintings that simply cannot be cleaned, because the image layer is so sensitive that no known cleaning agent can effectively remove the discoloration without causing extensive damage. When a conservator doubts the survival of the image, the choice is sometimes made to leave the painting alone.
Similar consideration must also be given to the frame that surrounds the work of art. They possess the same sensitivities to solvents and cleaning agents as the art itself. Often times, the frame is more elaborate and decorative than the painting. Gold or silver leafed frames should never be wiped or cleaned with water or household cleaners. A clean soft brush or feather duster can be used to remove surface dirt and grime.
It is important to visually inspect paintings and frames regularly. Look for changes in or on the decorative surface. Loose canvas or small cracks that develop should signal a problem with the art or environmental conditions to which the art is exposed.