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 is the vehicle system used for the formulation, so that good tack properties of vehicles are crucial for good performance of lithographic 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.
Novomatics tack measuring instruments are designed for precise tack measurements for infra- and inter-laboratory usage in QC and R&D. Beside the correct tack measuring parameter valuable additional information are provided in same test, for instance, maximal surface stress on substrate, splitting behavior (short or longer strings) and so its misting tendency under various press conform conditions.