All paintings change and deteriorate with age. Accidents happen, natural elements strike. And even if the artwork lived a good, safe life, the natural aging process takes place; varnishes yellow, dirt and grime accumulates on the surface changing the visual impact and stability of the painting.
Understanding the range and the cause of damage in a painting and recommending the best treatment requires knowledge and experience. Good art conservators are artists trained in chemistry, art history, technology of materials; they are crafty, patient and always apprehensive of things gone wrong.
The choice of an experienced art conservator, if you are looking for one, is a crucial one. Almost every older painting has been restored at least once before. It is a sad truth that many times the most damage done to a painting is from an inept restoration in past. Not so long ago, the craft of restoring paintings was entrusted to local artists. Some attempts at restoration caused irreversible damage and we can now only sigh and imagine what the painting was supposed to look like. And the cycle of bad restoration is not over yet – just about every framing shop offers "restoration" services, mostly performed by the master framer himself.
It is important to remember that improper restoration can affect the value of a painting negatively, and that many times previous restoration damage cannot be fully corrected.
As a member of the American Institute for Conservation, in my work I strictly follow their code of ethics. Every painting is treated with the utmost care and respect, and the treatment is fully reversible, documented and done with great consideration of the artist's intentions. See for yourselves.