How Humidity Affects Printers December 8, 2021 Edge OneCraig's Corner No Comments Moisture in Paper? Yes, paper is hygroscopic. This means it picks up moisture from its environment and it will release moisture into the environment to try to reach equilibrium with the moisture in the air. Moisture content is important in inkjet, laser, and offset printing. The first thing to understand is the importance of purchasing and using paper with the right moisture content. The second thing is to try and maintain stable moisture content with your paper handling to try to work within the recommended specifications. The moisture content is measured as relative humidity and it affects the amount of moisture in paper. Typical, paper is produced to an absolute moisture content between 4.0 and 6.0%, meaning 4 to 6% of the paper’s total weight is made up of water. But once unpacked, the paper can either absorb or dissipate moisture. Most papers are designed to be stable in a 45-55% relative humidity (RH) at 72°F environment. Different printing processes work best with certain amounts of moisture. In digital printing, the moisture content can affect the toner adhesion, paper jams and the fuser roller temperature. Inkjet is affected by many of the same issues, but is even more susceptible to dot gain or ink spreading, drying delays, and ink show through. Paper Handling Best Practices Store the paper in a room where the temperature and humidity are controlled. If that is not possible, leave the paper in the room that it will be printed in for 24 hours. Keep the paper shrink wrapped and away from outside walls. Before you remove the wrap, make sure that the paper is the same temperature as the surrounding air. Acclimate the paper after printing to allow moisture return (offset, laser) or “outgas” (inkjet) Paper’s propensity to absorb water can affect the function of printers in moist environments. If you want to explore how humidity affects printers, it’s important to note that the impact depends on the type of printer and paper. However, the following observations typically apply: HIGH HUMIDITY When a printer resides in a humid environment, the moisture content can distort the paper, making it warped, wavy, or curled. This can disrupt the function of the printer and cause paper jams. It can also cause streaks and smudging during the printing process, diminishing the print quality. Finally, pages may stick together, printed sections may become overly saturated, and toner may peel from the page (leaving blank spots). LOW HUMIDITY When humidity is removed from the air surrounding a printer, multiple sheets of paper may feed at the same time; this is especially frustrating when printing double-sided sheets. Dry paper is also more prone to static electricity, which can cause the paper to jam in the printer. In addition, dry air can cause ink clogs within the printer, very light or faded print and text/images appearing to spread out or repeat due to the paper shrinking.