These are relief reduction prints. In relief printmaking the surface of a printing plate (wood, linoleum, or a synthetic substitute) is carved with sharp tools. Ink is applied to the surface of the printing plate with a roller; only those areas of the plate where material has not been removed by the carving tools will accept the ink. A piece of paper is laid on top of the plate and the ink on the plate is transferred to the paper. In the reduction technique, after the first color has been printed on several sheets of paper, more material is cut away from the printing plate and a second color of ink is applied to the plate and printed on the papers. Subsequent carving and printing can continue until the artist has completed the image. When the edition is completed, the printing plate cannot be used for any more prints because most of the image will have been carved away in the process.