Since art forgery is a very big business, enormous sums of money are involved, and the successful passing off of a fake will be very rewarding. In consequence, a great deal of ingenuity is devoted to establishing the authenticity of a work of art. In many instances its provenance (place of origin) and its successive owners, in the case of an historical work, are known, and its authenticity, if not its quality, is unchallengeable. Many works in public galleries and private collections are of this order.

Frequently, however, there are gaps in the histories of many works— sometimes covering many centuries. In these circumstances the internal evidence in the work itself—its material, its finish, its condition, its similarity to other works by the same artist from the same period—has to be considered and specialist expertise consulted.