In this test, tack graded inks have been tested for their ability to trap overprint colours. A set of inks with ascending and a set with descending tack values were tested to compare the different results. The inks were each tested on one coated and one uncoated substrate. Tack-reduced inks were created by mixing the regular inks with linseed oil. This allowed both samples to be printed using a CMY colour sequence but with opposite tack order. The purpose of this test was to discover how much of an influence tack has on multicolour printing, specifically colour reproduction. Preucil's trap equation and colour hexagons were used to determine the outcome of this experiment. The results of this test showed that the descending tack order inks resulted in slightly better trap values on both coated and uncoated paper. The colour gamut produced by the colour hexagons also showed a slightly larger gamut for the descending tack inks. It was found that there are many factors which influence tack and trap. Resins and additives in ink influence its original tack value. On press, tack increases as speed increases, and tack increases as ink film thickness is lowered. As temperature increases, tack decreases and press design will influence how well colours trap. There are also many factors which influence the colour sequence chosen other than tack values such as colour reproduction, moire, and transparency. When trying to solve these problems tack should still be taken into consideration when moving colours on press. One solution which allows for colours to be rearranged without changing tack sequence is to use quickset inks.
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