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
Printing or building up many thin layers of material in succession. The technique is also known as additive manufacturing, rapid prototyping, or fabricating. Gang run printing is a method in which multiple printing projects are placed on a common paper sheet in an effort to reduce printing costs and paper waste. Gang runs are generally used with sheet-fed printing presses and CMYK process color jobs, which require four separate plates that are hung on the plate cylinder of the press. Printers use the term "gang run" or "gang" to describe the practice of placing many print projects on the same oversized