A vibration or ripple sent through the inking system of an offset press when the ductor roller, alternately contacting the first oscillator (an ink roller) in the roller train and the ink fountain roller, first makes contact with the oscillator. Ductor shock does not have serious consequences for print quality as long as the form rollers are over the plate cylinder gap when the shock occurs. (See Inking System: Offset Lithography and Offset Lithography.)
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