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.
