From The Art and Popular Culture Encyclopedia
The Ben-Day Dots printing process, named after illustrator and printer Benjamin Day, is similar to Pointillism. Depending on the effect, color and optical illusion needed, small colored dots are closely-spaced, widely-spaced or overlapping. Magenta dots, for example, are widely-spaced to create pink. 1950s and 1960s pulp comic books used Ben-Day dots in the four process colors (cyan, magenta, yellow and black) to inexpensively create shading and secondary colors such as green, purple, orange and flesh tones.
Ben-Day dots differ from halftone dots in that the Ben-Day dots are always of equal size and distribution in a specific area. To apply the dots to a drawing the artist would purchase transparent overlay sheets from a stationery supplier. The sheets were available in a wide variety of dot size and distribution, which gave the artist a range of tones to use in the work. The overlay material was cut in the shapes of the tonal areas desired—i.e. shadow or background or surface treatment and rubbed onto the specific areas of the drawing with a burnisher. When photographically reproduced as a line cut for letterpress printing, the areas of Ben-Day overlay provided tonal shading to the printing plate.
Ben-Day dots were considered the hallmark of American artist Roy Lichtenstein, who enlarged and exaggerated them in many of his paintings and sculptures, especially his interpretations of contemporary comicbook and magazine images. Other illustrators and graphic designers have used enlarged Ben-Day dots in print media for a similar effect.