Any advice about cleaning an oil painting that's covered in dust or yellowed varnish must come with a major disclaimer. More than other kinds of do-it-yourself projects, cleaning oil paintings should really be trusted to expert conservators. However, if your painting is not that old, not terribly valuable, or not too important, there are a few possible ways to make it look brighter and cleaner yourself. Furthermore, altering true antiques almost always decreases their value, whether or not they look better to you.