The problem of separating the authentic from the imitative is one of the great pleasures of art history. Traditionally, it has been the human eye, appraising with a certain educated feeling of the connoisseur, that determined whether a painting was autograph, derivative, or merely fraudulent.It is sometimes difficult, however, to judge the style of a painting due to alterations of the varnish and paint surfaces. Museum paintings of a certain age are often obscured by discolored varnish and old restorations. It is the traditional function of the art restorer, also known as a conservator, to stabilize any deterioration within the art object such as flaking paint or a weakened support. The conservator may periodically be called upon to remove the uppermost layer of discolored varnish to allow a proper viewing