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Chapter 10

GCM 110 Chapter Notes - Chapter 10: Toner, Free Newspaper, Laser Printing


Department
Graphic Communications
Course Code
GCM 110
Professor
Diana Brown
Chapter
10

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GCM110- Pocket Pal Readings
Properties of Paper
Grain Direction (PP 190)
Grain: refers to the position of the fibers (important for printing and binding)
- During papermaking, most fibers are oriented with their length parallel of the paper
machine (machine direction) and their width running across the machine (cross
direction)
- Paper folds smoothly with the grain direction and cracks when folding cross-grain, Is
stiffer in the grain direction, expands/contracts more in cross direction when exposed to
changes in moisture
Basis Weight (PP 191-192)
Basis Weight: the weight in pounds of a ream (500 sheets) in the basic size for that grade of
paper. Or, it is the weight of 1 m2 of paper and is expressed in g/m2
Ex: Basis 70 means that 500 sheets 25x38 inches of book paper weigh 70 pounds = 104 g/m2
- Paper is commonly identified by ream weight: 20-pound bond, 70-pound coated, etc.
Metric system: In the U.S, basis weight is referred to as grammage, and is expressed as weight
per unit area, or grams per square meter (g/m2)
Thickness: also known as the caliper, and is measured in mils or thousandths of an inch. It is
different from bulk of the paper (which is the thickness of a book). Bulk is expressed as the
number of pages per inch (ppi) for a given basis weight
Strength: the strength of a paper is more dependent on the nature of its fibers than its
thickness. Tear resistance in the cross-machine direction is always higher than in the machine
direction because the greatest number of fibers lie across the path of the cross-machine tear
Stretch: is the amount of distortion paper undergoes under tensile (tension) strain. Stretch is
greater in the cross direction than in the machine direction
Paper Grades and Basic Sizes (PP 196-199)
-Web offset paper has its grain direction parallel to the direction of web travel
- Rolls must be properly wound, protected, and have good tension strength to minimize
tearing or web breaking
Paper Testing and Evaluation for Printability
- Letterpress testing for smoothness, coverage, and ink receptivity can be done on special
test proof presses
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