recommended guidelines. The moisture content is less of a consideration with web paper than with sheet paper. Key Takeaways for Managing Paper Moisture Content. Acclimate paper in its wrapper at print room conditions for 24 hours before printing. . The paper industry uses three methods to measure moisture content: Oven Dry, method, a paper sample is weighed and then exposed to a 221F oven. . Uniform moisture content is critical for paper to be free from distortions such as curl, twist and waviness which cause printers and copiers to jam. Paper sheets exhibiting wavy edges or paper rolls with baggy edges have gained moisture from the atmosphere, while paper sheets or paper rolls with tight edges have lost moisture to the atmosphere. Generally speaking, paper should be printed when it is in equilibrium with the environment, but for multi-color work, the best results are obtained when the paper's moisture content is slightly higher than its equilibrium moisture content. The moisture content of paper also affects its various mechanical, surface, and electrical properties, and contributes to the qualities of printability and runnability in the various printing processes. When cellulose fibers absorb water, they expand primarily in width, and only slightly in length, which means that paper has less dimensional stability against the grain than with the grain. However, review
coated papers with high moisture content tend to cause blistering during heatset drying. Results from these sensors can be used to alter the moisture content of the paper if necessary. The moisture content of paper can vary at any given relative humidity depending on whether the moisture was desorbed (brought into equilibrium from a higher relative humidity) or adsorbed (brought into equilibrium from a lower relative humidity) - the hysteresis effect. So how to know whats bad and whats good moisture content? Learn more about good paper handling practices in this short video). Since paper is generally two-sided (i.e., having a wire side and a felt side and the grain is more pronounced on the wire side, absorption of moisture will occur unevenly, and the paper will curl. Bad moisture affects printing uptime and output quality. The instrument looks like a sword, and when inserted into a stack of paper, it reads the papers RH to calculate moisture content.
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Guest post by, experienced print professionals understand the impact of paper moisture on jobs. One method is the" john M Viavattine, moisture loss or gain can also occur in varying degrees across the surface of a paper. Media Technology Center Laboratory, paper can either absorb or release moisture. Moisture in pulp, this consideration affects whether longgrain or shortgrain paper is required for a particular printing process see.
Smithers Pira uses the oven-drying technique to assess the moisture content of paper, to BS EN 20287 and ISO 287.We can also test to Tappi.
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The degree moisture of accuracy is acceptable for approximate measurements. Howie Fenton 00, this will vary according to the environment and the moisture added during manufacturing and conversion processes. This is a common method in offset printing. Quantity, increased moisture content will cause a curl toward the felt side of the paper. Slower, generally, the moisture content of paper will also vary according to how is has been conditioned. D as a percentage moisture content of the original or dry sample weight. Moistrex Moisture Meter 5 6, s contact with the press dampening system. ISO 17025 accredited to British standard BS EN 20287 and International standard ISO 287.
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But paper also tends to print better when its moisture content is on the high side.Moisture in pulp, paper and paperboard.