To obtain the emulsion, watercolor pigments are mixed with a solution of gum arabic. This pigmented colloid is then mixed with a light-sensitive dichromate salt to form the viscous emulsion. The emulsion is brushed onto watercolor paper, allowed to dry in the dark, and then contact printed using a UV source for exposure.
Ultraviolet radiation exposes the chromium salt and forms a very weak image.
However, the exposure effect is magnified in the image due to the reaction of the dichromate with the gum arabic component of the emulsion. The gum solution hardens in proportion to the extent of dichromate exposure, trapping the watercolor pigment in the hardened layer. Where exposure is heavy, a greater proportion of pigmented gum is hardened and adheres to the paper support. Multiple coating and exposure cycles are often needed to build the image to desired strength. When wet, the emulsion layer is very fragile and areas of the wet image layer can be removed selectively.