Excessive foam present in the printing unit, tray or ink pump unit.
Causes:
Incorrect solvent balance;
Incorrect pH or viscosity;
A one to one roller ratio at speed;
Ink pump speeds causing violent action and shear;
Ink pump unit and return pipe mixing air with the ink;
Lack of defoaming agent in ink formulation;
Contaminated ink that has been returned to ink store;
Solutions:
- Add rich solvent (ester) to redress the ink mix;
- Adjust pH and reduce viscosity (make very small additions of defoamer);
- Reduce ratio of fountain roller;
- Reduce pump speed or rate of flow to minimum required. Adjust hose height;
- Ensure returned 'foamed ink' is mixed/agitated in the sump/bucket with fresh non-foamed ink. Lower the return pipe to ink level in pump
- Add defoaming agent to ink;
- Replace with fresh ink;
