Gum bichromate negatives of cyan, magenta, and yellow or red, green, and blue are used for a full-color image. Some photographers prefer substituting the cyan emulsion in the CMYK separations with a cyanotype layer. A simple duotone separation combining orange watercolor pigment and a cyanotype can yield surprisingly beautiful results. Low density photographic negatives of the same size as the final image are used for exposing the print. No enlarger is used, but instead, a contact printing frame or vacuum exposure frame is used with an ultraviolet light source such as a mercury vapor lamp, a common fluorescent black light, or the
Color printing are not the primary colors. Using a limited number of color inks, or specific color inks in addition to the primary colors, is referred to as "spot color" printing. Generally, spot-color inks are specific formulations that are designed to print alone, rather than to blend with other inks on the paper to produce various hues and shades. The range of available spot color inks, much like paint, is nearly unlimited, and much more varied than the colors that can be produced by four-color-process printing. Spot-color inks range from subtle pastels to intense fluorescents to reflective metallics. Color printing involves a