Strokes of paint added by an artist to correct or modify the various elements of a composition. Pentimenti are invaluable for the art historian in that they reveal the act of creation. These can be observed with the naked eye as the surface layers of paint begin to fade, or through x-rays. A painting where the pentimenti provide a wealth of information is Caravaggio's Martyrdom of St. Matthew in the Contarelli Chapel, Rome (1599-1600, 1602). Caravaggio painted alla prima, a method that results in many pentimenti as the artist who uses it works out the composition directly on the panel or canvas. The pentimenti in Caravaggio's work, seen through x-rays, reveal his lack of confidence in tackling the complex composition. The contract for this work called for a scene in a church interior with steps leading up to it and many figures. The x-rays show that the figures were originally smaller and that many modifications were also made to the overall arrangement of the interior space.
Historical dictionary of Renaissance art. Lilian H. Zirpolo. 2008.