Ink dried on plates and rollers and not transferring to substrate, normally found on leading edge of substrate.
Causes:
– Low pH due to loss of amine;
– Uncontrolled viscosity;
– Air spillage onto printing unit;
– Incorrect solvent balance;
– Insufficient transfer;
– Web temperature too high when entering print station;
– High temperature and/or low humidity in pressroom.
Solutions:
– Add pH stabiliser solution;
– Maintain correct printing viscosity. Do not print at high viscosity;
– Keep forced air away from units. Air movement near doors, windows and fans is to be avoided. Check interdeck dryers for overflow;
– Use correct solvent mixture, weak solvents will precipitate ink components;
– Use correct anilox. Do not use very low viscosity;
– Reduce preheat web temperature entering print station;
– Control pressroom environment to optimum conditions.
