Problems with printing? Paper wetting may be to blame

When encountering unidentified printing problems, one can run into real frustration. Little do we know that an invisible pest in the form of moisture can be behind our difficulties. It can cause problems when printing due to its effect on two different physical elements: paper and ink or toner. In most cases, keeping it at the right level is enough.

Moisture control is critical to print quality

Most uninitiated business people don’t realize that paper absorbs moisture from the air, which can have a negative impact on print quality. The fibers in paper easily absorb ambient moisture, which can alter the physical structure of the paper and the overall print quality. In other words, paper is highly hygroscopic in nature. To better understand the importance of moisture in the printing industry, as well as possible solutions to this problem, we’ve created a brief guide on how paper properties are related to moisture.

While there are many reasons why proper moisture control is essential in the printing industry, there are a few main benefits that can always be referenced. For example, print quality improves with proper moisture levels because it helps get rid of paper distortion and prevents electrification.

Machine operation also becomes more efficient as proper moisture levels directly contribute to reduced downtime. This is due in part to ensuring fewer paper jams and less paper sticking together. Overall, printing in a well-balanced environment ensures a consistent level of quality, reduces waste and extends the life cycle of cylinders and plates.

Paper hygroscopicity

Paper tries to maintain a balance with the moisture in the environment. To do this, it will collect and release moisture from its environment. When paper is manufactured, typically 4-6% of its weight is composed of water. After packaging, the amount changes depending on the humidity in the room. The total relative humidity in the room plays an important role in printing because different printing processes work best with different paper humidity.

Digital printing

With digital printing, the amount of moisture in the paper can affect toner adhesion and cause problems with roller temperature, causing paper jams. With digital printing, you need paper with a relative humidity of about 50-55% for optimal printing. If the humidity level drops below 40% RH, the paper loses water and begins to change shape. It can even cause static electricity to appear between the sheets, sticking together and attracting dust. Combined with the equipment problems we wrote about earlier, this can even lead to damaged equipment and the production of defective print runs.

In offset printing, the moisture content can affect the interaction between ink and press, paper and press, and ink and paper. A higher humidity level is needed there, around 55%. If the relative humidity is lower, dry air will cause problems such as curling, creasing and dot doubling. With low humidity, static buildup is also common and can cause jams, as well as stacking, trimming and folding problems when the paper starts to stick together. And when the paper passes through the printer again, it can change shape again and cause cracking along the folds after printing.

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