GCM 240 Chapter Notes - Chapter 5: Hygroscopy, Metric System, Cellulose
30 Sep 2016
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Weight of paper is described as either basis weight or grammage. Basis weight: the weight in pounds of a ream of paper cut to its basic size. Basic size: the sheet size in inches of a particular type of paper (standard) Nominal weight: the basis weight for ordering and specifying paper and the basis weight to which it is made. Grammage: the weight in grams of a single sheet of paper having an area of. 1m2 (1m x 1m: metric system, units are g/m2. Basis weight is affected by moisture content and will increase as paper gains moisture and decreases as it loses moisture. Moisture content of paper affects paper properties like dimensional stability. Cellulose fibers are hygroscopic: strong attraction for water. Fibers become larger upon absorbing moisture and become smaller upon giving up moisture. Change in moisture content of paper therefore causes register problems, curl, and paper distortion.
