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Novomatics Operation Manual
2. Importance of tack measurement in the printing ink
industry
2.1.
What is tack?
Tack is a measure of the forces required to split a single film into two. In case of ink, such
film splitting is influenced by rheological and adhesive ink properties and the internal
cohesion of the ink.
Tack depends heavily on the ink formulation. Inks must be formulated to optimize the quality
of printing and minimize undesired effects in the printing process, such as substrate rupture
or coating pick-up, web contamination, dot gain, poor setting, loss of gloss, loss of color
density etc. that can be caused by too high or too low tack.
When tack is too high it is hard to separate the paper from the printing blanket or when it is
too low the ink does not transfer properly down the inking roller chain. A major influence on
ink tack has the vehicle system used for the formulation, so that good tack properties of
vehicles are crucial for good performance of litho inks on the press.
Tack is a critical issue in the lithographic process and tack is relevant to all stages of
distribution or transfer in the printing process. Therefore, accurate tack measurements are
essential for a good performance of ink on the press.
2.2.
How to measure ink tack?
Conventional instruments being developed to measure tack all rely on the same principle of
measuring the force exerted on a measuring roller that is positioned on the ink film of a
driven roller. This method suffers various disadvantages due to the fact that the result of both
compression and splitting forces are measured.
In addition to this, different manufacturers of tackmeters have established their own arbitrary
scales, so that it is difficult to compare the results of tack measurements of an instrument
from "manufacturer A" with the ones from a "manufacturer B". Even comparability of
measurement results of instruments from a single manufacturer is difficult, mainly due to the
fact that different viscoelastic properties of the measuring elastomer roller and the wear of
bearings causing differences in tack reading. The AlphaTackPlus test method is a
breakthrough in tack measuring technology by elimination of errors caused by these effects.
AlphaTackPlus
5
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