A print fault on corrugated substrate characterised by darker lines appearing at the flutes from the uneven surface of the corrugated board. It is caused by the liner as it dips lower where there is no flute and higher where there is a flute. Superimposing one colour on another so that the first colour down is sufficiently dry before the next colour is printed.
Causes:
– Calliper variations in corrugated substrates corresponding with flute profile;
– Incorrect plate impression;
– Substrate surface resist to ink lay and wetting;
– Ink film too thick for high hold-out substrates;
– Ink film too thin for the coverage between flute tip and valley;
– Ink viscosity too low;
Solutions:
– Improve corrugated process by reducing starch application and good liner selection to eliminate washboard at corrugator;
– Adjust plate to substrate impression;
– Check additives used with ink supplier;
– Reduce ink film thickness or use more porous substrate;
– Improve corrugation process, increase ink thickness or change ink formula for more ink transfer;
– Raise viscosity with fresh ink;
