BEN DAY PROCESS, a medium invented about 1879 by Benjamin Day for use in photomechanical engraving for adding tints, shading or stippling to line engravings. Its use eliminates the shading of a drawing by hand and, being mechanical, it avoids the irregularities of hand-drawn work. A numerous and varied selection of mediums, including straight, wave, curved and grad uated-line tints; grain stipples and textures; and hand and me chanical-stipples, are available. The drawing, executed in all par ticulars as for reproduction as a line engraving, that is, drawn in India ink upon a white background, is photographed by the photo engraver and a negative of the ultimate size of the engraving secured. From this negative a faint image is printed upon the sensitized zinc. Areas not to have Ben Day are painted out on the zinc with gum gamboge. The Ben Day medium, which is in relief, is inked with acid-resisting ink and printed upon the zinc. The zinc is now washed with water to remove the gamboge and then etched in the regular way. When several different tints and shad ings are required on a single engraving, each required tint must be separately inked and printed on the zinc, the engraver covering up such areas where the shading is not to print. The ordinary method of indicating on the drawing the portions to be shaded is to paste a transparent flap upon it and mark the areas of each Ben Day with coloured crayon, although where only one tint is to be used the drawing itself is sometimes marked with a light blue wash. A more unusual use of Ben Day is the making of a set of four-line engravings from a single black and white drawing, setting up the tints in such a way that when each separate engraving is printed progressively, one upon the other, with blue, yellow, red and black inks, a coloured illustration is secured which somewhat resembles, but does not equal, four-colour process printing.