An oil painting can be cleaned by rubbing the surface with a plain piece of white bread, then dust off the crumbs. NEVER try to clean a watercolor or pastel painting.
Source: I paint and have learned these tips in the course of my studies.
By Maya from Redlands, CA
Any ideas on how to clean a dirty oil painting at home?
Minna from Umited Kingdom
I'm an artist and I would suggest you have it professionally cleaned. Even though I paint and have many of my own works, I would NEVER attempt to clean them myself. You could destroy the surface and then the value of the painting would be less too. Hope this helps you out.
An artist once suggested a weak solution of methylated spirit, dabbed on very gently with a lint-free cloth. I tried this and it did lighten the painting, bringing some areas to visibility. However the painting was already old and crazed so I wasn't too scared of damaging it - I would be reluctant to try this on something more valuable and agree you should have it professionally cleaned.