Definition of "underpaint"

underpaint

verb
third-person singular simple present underpaints, present participle underpainting, simple past and past participle underpainted
1. To rough in the colors of a painted work of art, prior to painting the final version.
  Quotations
  The underpainting should be neutral and preferably cool in color. Positive colors may be underpainted with shaded tints of the full color. This is especially true of blues and reds because the oil glazes darken or fade. Reds are best underpainted with vermillion or cadmium.
  1939, John Sloan, “Painting”, in Gist of Art, New York, N.Y.: American Artists Group, Inc., page 136
  Fidelman underpaints the canvas and after it is dry begins the figure of Venus as the conspirators look on sucking their breaths.
  1969, Bernard Malamud, Pictures of Fidelman: An Exhibition, New York, N.Y.: Dell Publishing Co., Inc., published 1970, page 84
  In spite of the dramatically different light in these paintings, I underpainted all of them with the same color, Quinacridone Gold. In High Point, I underpainted the entire painting to give it that warm glow. In the others, I underpainted the foreground with two light washes and the middle ground with one light wash.
  2006, Rachel Rubin Wolf, Splash 9: Watercolor Secrets, Cincinnati, Oh.: North Light Books, F+W Publications, Inc., page 111