The separator, which for much of comics history was Chemical Color Plate in Connecticut, would make nine acetate prints of the original art, one for each percentage of each color.
The black and white artwork – originally drawn at twice the printed size, then 1½ times, and currently slightly less than that — was photographed, reduced and printed on sheets of clear acetate. Nine copies were made of each page – one for each of the three percentages of the three colors – and these were turned over to a separator.
Using the colored artwork as a guide, areas on the acetates would be filled in with an opaque paint (Rubylith) to correspond to the color(s) necessary.
Once the color guides were fully “translated” and the acetates were finished, they would be photographed with appropriate screens to create a single version which included the percentage dots and the solid of one color. These three new pieces of film, along with a fourth clean version of the art which was used to make the black, were used to make the printing plates.