Paintings in the preservation process will inevitably darken yellow, which is a result of the surface oxidized varnish. So far there is not a varnish is not oxidized, clear out old light oil re-work the only way to restore the original appearance of the light. Cleaning solvents are used:
(1) turpentine. The role of the old painting weak, while the new color layer is stronger, especially after use with hot water heating for better results.
(2) purified gasoline and benzene (toluene, xylene). The solubility of the resin is stronger than turpentine.
(3) in ethanol (absolute alcohol) and methanol (wood alcohol). Is a powerful solvent of the resin.
(4) acetone and chloroform. Can quickly dissolve the resin and oil. Art supplies store sold several solvent cleaning agents are generally mixed, strong solvents can be used alone. Modern paintings use more resin varnish, turpentine can be cleansed. Older and more domestic oil painters use oil varnish, turpentine and require the use of ethanol blended. The acetone wash ancient works only when used as an additive.
(5) hydrogen peroxide. There are many valuable substance is a white pigment lead salt, containing a trace amount of hydrogen sulfide gas in the air, when the encounter lead sulfide ions, chemical reaction occurs, almost black solid birth lead sulfide, so paintings darker and hydrogen peroxide can lead sulfide oxidation of white lead sulfate
Wipe Method: Using white cotton balls (medicine stores) dipped in a circular wiping clean detergent from the corner of the screen, each part of the time is not easy to wipe too long, to avoid damage to the color layer. After the cotton is stained yellow varnish to immediately replace the new one. Most of the old varnish can be cleansed first pass, the second time for cleaning stubborn part of a strong solvent can be added. Squeeze and damage caused by dirty and fly feces stains can use the tool to clear.