In art history, especially painting research, underdrawing describes a preliminary drawing carried out by the artist, which is located directly on the primer of the picture carrier and is covered by one or more layers of paint. It can therefore usually not be perceived by the human eye. The term underdrawing is used to differentiate the more general term preliminary drawing, which also includes preliminary studies by an artist that were made separately on paper or cardboard.
Older paintings are mostly signed in some form. Art history distinguishes between two basic techniques:
The scratching with a needle, as can be found especially in medieval paintings with gilded grounds
The use of painting and drawing materials, such as those used for hand drawings, including graphite, charcoal, chalk, ink, Indian ink and white lead (opaque white)
The visualization of underdrawings harbors great potential for research in art history with regard to questions about the creation processes (work genesis), the materials used and the execution techniques as well as attribution and authenticity (original or copy).
Today, with the methods of multispectral photography, especially infrared reflectography (formerly also infrared photography), different layers and painting materials of a painting can be made visible and scientifically analyzed.