What is the story on process color ink tacks and color sequences?
A.: Tack has to do with the stickiness of an ink. As an example, there are sheetfed inks that are so stiff they nearly break your ink knife trying to get some out of the can. On the other hand there are other colors that are so runny they barely stay on the ink knife. Both of these inks could have the same “tack.” The difference is in the “body” of the ink and has little to do with the stickiness of the ink, although the two are somewhat related. To insure proper “trapping” on a multi-color press, most sheetfed process inks are “step tacked.” What this means is, that the first color printed must be the highest in tack so that successive colors of wet ink will stick to the colors already printed on the sheet. (An alternative to “step-tacked” process inks is the “unitack” system, more popular in some foreign countries, wherein all colors are the same tack). Those of you who have overprinted colors on a T-51 color head or other presses using a common offset printing blanket, will better u
