How viscosity effects multiple aspects of print-ability.

1. Viscosity

2. The viscosity of an ink will affect many aspects of printability
including
print strength
print sharpness
 ink lay and color
drying speed
 foaming
Viscosity is one of the easiest variables to change on press and
along with pH has the most significant effect on the resulting print
quality and ink performance.
An important rule is that a running viscosity range is established
and maintained in order to achieve the highest consistent quality
you can achieve from your ink systems.
All water-based inks tend to be thixotropic, which means the liquid
will show a moderate drop in viscosity when agitated.

3. Signs you are experiencing Viscosity
Troubles:
Color Variation: Maintaining viscosity is crucial in color consistency throughout a press run.
Excessive Ink Usage During a Press Run: As solvent evaporates, more ink tends to be applied to the substrate,
therefore you may notice you are cruising through your ink more than normal.
Ink Smears/ Dirty Print: If the ink viscosity is not adequately maintained throughout a press run, the ink viscosity
rises and falls due to solvent evaporation and replacement. The ink may buildup on the plate, impression roller or
substrate outside of the impression area. This can cause dirty print or smearing in non-image areas.
Cells Plugging in your Anilox: Improperly maintained or inadequately mixed inks can result in ink solids trapped in the
anilox cell creating print imperfections. Additionally, ink viscosity directly affects the transfer of ink from the anilox
roll to the plate. This changes the volume of ink applied to the substrate and therefore the color and intensity of the
image. This is the reason that many printers use different anilox rolls at different times of the day or year.
Excessive clean up time due to ink related issues: If you have housekeeping issues around the ink pail and
throughout the press, you may have a viscosity related problem. Ink management, including viscosity control and
mixing, can aid in clean up time on press.

4. Viscosity Management on
Press
Put ink on press and allow to circulate 2-5 minutes. Then, check
viscosity. If viscosity is high, cut using water. If ink is too low in
viscosity, add fresh ink to bring it back into spec. If ink is over
saturated with water, it may not be possible to bring ink back to
suggested printing viscosity and ink may have to be discarded and
fresh ink put on press.
Generally, a 1 % water cut will lower viscosity 1-3 seconds in a BYK
Gardner 2/z cup.
The viscosity of ink on press should be checked frequently, once
an hour is recommended, every four-hour minimum and adjusted
accordingly to keep within spec.

5. Lower than suggested
viscosity
Higher than suggested
viscosity