Cleaning solution for printing plates

1,074,289. Cleaning printing plates. KALLE A.G. Oct. 2, 1964 [Oct. 4, 1963], No. 40257/64. Heading B6C. [Also in Division G2] Tone is removed from the non-image areas of an exposed negative working light-sensitive material during or after preparation therefrom of a planographic or offset printing plate by treating the material or plate with cleaning solution comprising a lacquer- and greasedissolving organic solvent and a small amount (at least 0.01 equivalents/litre) of HC1, HBr or a salt of either of them with an organic amine or amide having a dissociation constant below 10-3 at 25‹ C. The treatment may be carried out after inking up or lacquering the plate, or after development but prior to inking up or lacquering, or even immediately after exposure. In the latter case the cleaning solution may in certain cases also be used as the developing solution. The treatment may be repeated one or more times, the plate being cleaned with water after each treatment. A wide variety of solvents is specified, and the solutions may also contain water, an alcohol, a hydrocarbon, a dye, and/or a cellulose ether, suitable examples being given.