ABSTRACT
Gum is immensely flexible and variable. At any one stage there are different choices to make: choices such as paper type, sizing type, pigment color, amount of pigment in the coating mix, dichromate kind and strength, gum brand, coating thickness, length of time before exposure, length of exposure, kind of exposure, length of time after exposure and before development, development time and technique, temperature of water development, and so on and so forth. All of these different choices can be a bit daunting to a beginning gum printer, especially if things go awry. Luckily there are four main problems with four common causes: the gum layer washes all off, the gum layer does not wash off, the gum layer flakes off and the highlights are muddy or stained. The contrast issue is a very common problem in gum printing. This should be solved at the digital negative stage, with an appropriate contrast adjustment curve.
