Sometimes, linting can also be caused by dust when the paper is rolled up and cut into the desired width and diameter. We talk about negative and positive linting, where negative is visible on unprinted areas and positive is visible on printed areas.
Problems with linting are most common in heatset web offset printing, but the phenomenon occurs in all printing methods and is dependent on the paper grade to a greater or lesser degree. For obvious reasons, uncoated, bulky paper has more loose material on the surface than its coated equivalents.
When does linting occur?
Linting occurs during the printing process, when the web is dampened and inked, and causes the images to gradually fade and that parts of them have no colour. The problem most commonly arises in the first print unit, which in heatset generally is black (the print order is usually black, cyan, magenta and finally yellow, KCMY [link to text on CMYK inks]). The first colour picks up more of any free or loosely bound material present and so suffers more deterioration in the print result. In some troubling cases, fibres and fillers can enter the actual inking system, resulting in the costly task of emptying and cleaning the ink fountain and rollers in the printing unit.
Does the ink play a role?
The short answer is yes, the choice of ink affects the risk of linting. It is important that you choose an ink that is tailored to your choice of paper. Using the right ink ensures good functionality throughout the printing process. In other words, printing on an uncoated paper using an ink that is actually designed for a coated paper causes a considerable risk of linting. The print density is also important and needs to be adapted to the inks and the paper. If the ink density is too high for your paper type, you risk linting.
Ink coverage how much of the surface that is covered with ink, is a limiting factor for certain paper types. It is common to talk about a TAC value (total area covered). Coated papers generally have a higher TAC than uncoated papers. If the ink coverage during printing is not tailored to your paper, there is a greater risk of linting.
How can I solve a linting problem?
There are several ways to deal with linting, but the best option for you will depend on exactly where the root of the problem lies. Basically, the cause of the issue determines the appropriate course of action. It might be that you need to do a range of things, such as checking the inks, and possibly switching to an ink that has been developed for your choice of paper. One measure you can take straight away is to reduce the amount of ink applied by reducing the ink density.
If you need help with minimising linting or any other printing issues, contact Holmen Paper’s Technical Support team and they’ll help you to find the best solution to your specific problem.