Under-drawing is a preliminary drawing made on the prepared canvas, panel, or other support before the application of paint or any other medium and materials to be employed in the artwork. An under-drawing is obviously not meant to be seen after the work is completed, but it is sometimes visible to the naked eye in thinly painted passages, as well as in unfinished artworks. An under-drawing can also be revealed through infra-red photography or through the related technique of infra-red reflectography, which can achieve greater penetration of the paint layers.