Gum Etch

Also called 1:32 gum etch, a substance, produced by mixing one part 85% phosphoric acid with thirty-two parts of 14º Bé gum arabic, used to desensitize offset printing plates and/or chrome-plated dampening system rollers as a means of restoring their ink-repellency and water-receptivity. Metal dampeners can lose their water-receptivity over time or with use, as grease collects on their surfaces, and become increasing receptive to ink, which can produce a variety of press and printing problems. (See Dampening System.)

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