25. William Blake, The Marriage of Heaven and Hell copy F, plate 21. Relief etching, 15.3 x 10.8 cm., 1790, color printed and finished in watercolors and pen and ink c. 1794. Pierpont Morgan Library, New York. PML 63935. Detail of embossment of relief lines into the paper, caused by pressure sufficient to print from the shallows and relief simultaneously, and of the fine white lines between shallows and relief lines caused by the paper not picking up the color from the escarpments between relief plateaus and etched valleys.