What is the value of artist signatures?

An artist's signature can increase the price of an art piece by twofold. In most cases, an artist considers signing their work a valuable source of increased income. An artist's signature also attests to the authenticity of the work.

In certain cases, the economic value of a piece of artwork is tied up in the signature of the artist. For example, both Marc Chagall and Salvador Dali signed a blank piece of paper in which replicas of their famous works were planned to be made. These reproductions sold for a vast amount of money, even though neither artist ever saw the finished replica.