Many environmental pollutants alter the appearance of an oil painting. Varnish often is made of a natural resin that yellows with age. However, exposing an oil painting to cigarette smoke will increase the yellowing action and change the look of the varnish. Cleaning an oil painting is not something to consider if the damage is extensive. A professional conservator should deal with weighty dirt and nicotine build-up to preserve the painting. However, if the damage is slight, you can effectively clean the surface and reapply the varnish.
Use a soft paintbrush to remove surface dirt and dust from the painting. Flip the painting over and use the brush attachment of the vacuum cleaner to clean this area. Move the canvas carefully and avoid flexing the material, as this may cause paint to flake.
Lay out a sheet of brown or white paper in a well-ventilated area. This will be your workspace. Put on rubber gloves to protect your hands.
Dab neutraliser on a piece of cotton and wipe a test area. A neutraliser works as a cleaning agent. It also negates the chemical reaction of other strong solutions, such as varnish remover. Ideally, one would purchase a restoration kit with neutraliser included. For the best neutraliser product, consult a restoration expert; the local craft store will have the correct products, too. Look for an introductory cleaning kit or varnish-removal kit.
Apply emulsion cleaner to a wooden cotton swab. Dab at the test spot. Apply neutraliser to the area again immediately after using the emulsion cleaner. Repeat this process in a different spot with varnish remover. Look at the two test areas and determine which cleaner works best for this painting.
Choose the best product based on the testing. Work slowly in small areas until you clean the entire painting. Direct Portrait suggests applying the solution to a three- to four-inch square then immediately applying neutraliser before moving on to the next section.
Apply a varnish to the clean painting. Consult with the local craft store expert to determine which varnish will work best for your painting.
Start in the corner of the painting and work systematically. This will allow you to see the effects of the solutions on the paint before covering the entire surface.
Stop using any chemicals if they appear to damage the surface of the painting.