Causes for hazing
Hazing is visible a faint ink mist on non-engraved areas and leads to a higher ink density on engraved areas. Hazing is by far one of the most common printing defects in gravure printing and can be caused by many different factors.
Solutions for hazing
1) Ink viscosity is too high, leading to higher dynamic pressure. Check viscosity and adjust by adding solvent or additives accordingly.
2) Check ink for additives like binding agents.
3) Too smooth printing cylinders can lead to reduced lubrication between doctor blade and cylinder. Check your cylinder Rz values in chrome and copper, re-polish your cylinder. If problems persist, redo cylinder and change Rz values if necessary.
4) Check cylinder balance for bouncing and waviness, redo cylinder if necessary.
5) Check doctor blade holder for wavy blades and dirt. Clean holder and replace doctor blade and back up blade if necessary.
6) Check doctor blade setup, set for stiffer setup or use thicker backup blades.
7) If hazing appears one-sided, check if doctor blade holder is parallel to the printing cylinder axis.
8) Check doctor blade pressure. If too low, doctor blade will not hold back the dynamic pressure of the ink, if too high, doctor blade can bend, allowing ink through dynamic pressure to lift the blade tip. Use as much pressure as needed.
9) Check doctor blade angle. If the angle is too low, this allows dynamic pressure from the ink to lift the doctor blade.
10) Check doctor blade oscillation. Oscillation should be between 10 and 30mm and constantly move with jerks or stoppage time.
11) Check air gap between doctor blade and nip. If gap is too short, this does not allow residue to dry up before reaching the nip.
12) If air gap cannot be increased, use spotair to dry off residue. Be careful for dry-in in vignettes.
TKM recommends to use TKM CeraPrint