Hieronymus Bosch, Arrest of Christ and Christ Carrying the Cross from the Exterior of the Triptych of The Temptation of St. Anthony, 1505-1506, oil on panel, Museu Nacional de Arte Antiga, Lisbon, Artwork in the Public Domain via Wikimedia Commons.
French for the word gray, grisaille is the technique of painting in a muted monochrome palette. As would be expected, this technique often was used for the underpainting of a work of art; however, in the 15th century artists painted many exteriors of altarpieces in grisaille. It is possible that artists used the technique so that their paintings would resemble sculptures, but it may also have been chosen for its austerity which is well-suited for a closed altarpiece. The grisaille exterior set up the burst of color that appears on the interior when the altarpieces were opened on feast days and holidays.
