One colour bleeds into another. Colours do not overprint (trap) correctly. Ink picks off or transfers to press rollers. Print blocks in reels.
Causes:
– First colour down is drying too slowly or overprinted colour is drying too quickly;
– Ink being run too heavy in viscosity or anilox incorrect;
– Inadequate or unbalanced drying;
– Incorrect solvent balance;
– Low pressroom temperature and/or high humidify;
– Excessive press speeds.
Solutions:
– Adjust the drying speed and/or viscosity of the first ink down as low as possible. Adjust the viscosity of second ink down slightly higher. Adjust plate impression to the minimum required to achieve good print quality;
– Control ink viscosity. Check anilox specification. Check doctor blade and/or nip pressure;
– Dryer must be able to accommodate press speeds. Inter-station driers must be balanced;
– Check ink speed is correct for the type of work, e.g. process ink put on heavy two roll anilox system in error;
– Control pressroom environment to ideal conditions;
– Reduce press speed.
