Oil painting works will inevitably turn yellow and dark during the preservation process, which is the result of oxidation of the surface varnish. There is still no varnish that will not be oxidized. It is the only way to restore the paint l appearance of the original varnish. Common cleaning solvents are:
(1) Turpentine oil. It has a weak effect on the old oil painting and a strong effect on the new color layer, especially after heating with hot water.
(2) Refined gasoline and benzene (toluene, xylene). The solubility of the resin is stronger than that of turpentine.
(3) Ethanol (anhydrous alcohol) and methanol (wood alcohol). It is a strong solvent for resins.
(4) Acetone and chloroform. It quickly dissolves the resin and oil layer. Cleaning agents sold in art supplies stores are generally mixed with several solvents, and strong solvents cannot be used alone. Abstract art paintings are mostly made of resin varnish and can be washed away with turpentine. The older generation of oil painters in China use oily glazing oil, which requires the use of turpentine and anhydrous alcohol. Acetone is only used as an additive when cleaning ancient works.
(5) Hydrogen peroxide. There are many precious white pigment substances, which are lead salts. They contain trace amounts of hydrogen sulfide gas in the air. When hydrogen sulfide encounters lead ions, a chemical reaction occurs. The solid black sulfide is close to black, which makes the oil painting dark, and hydrogen peroxide. Lead sulfide can be oxidized to white lead sulfate .
Wiping method: Use a white cotton ball (available at a pharmacy store) to clean the detergent from the corner of the screen. The wipe time of each part is not too long, so as not to damage the color layer. Replace the new one immediately after the cotton ball is dyed with yellow varnish. Most of the old varnish can be washed away in the first pass, and a strong solvent can be added to the stubborn part during the second cleaning. Stains caused by damage due to squeezing and fly smudges can be removed with a knife.