Glossary

Question: What is the "Grain" of paper?

Answer: Paper is made up of many different types of fibers: wood, rag, plant, cloth, pulp. As the paper is made, a combination of fibers, pulp, chemicals, and water, flow through the paper making machine. The fibers align themselves with this flow. This direction or predominant orientation of the paper fibers, parallel to the flow on the paper making machine, is what makes up the grain direction of paper.

 

Question: What is the "Caliper" of paper?

Answer: Caliper is the thickness of a single sheet of paper measured with a tool called a micrometer. The measurement is expressed in thousandths (1/1000) of an inch.

 

Question: What is the "M-Weight" of paper?

Answer: M-weight (the M standing for the Roman numeral 1000) is the weight of 1000 sheets of a particular grade of paper, cut to a particular size.

 

Question: What is the "Basis Weight" of paper?

Answer: The paper industry has categorized paper into basically seven categories. These seven categories, with their seven basic established sizes, represent the foundation upon which all paper is related, one grade to the next. The seven categories are as follows: Book, Bond & Writing, Cover, Postcard & Bristol, Printing Bristol, Index, and Tag. The basis weight is the weight of 500 sheets (a ream) of paper in the basic size for that grade. An example would be 500 sheets of sub. 80 cover paper in its basis size of 20 x 26, would weigh 80 lbs.

 

Question: What is the "Opacity" of paper?

Answer: Opacity is the ability of paper to prevent print from showing through on the unprinted side. Usually the lower the basis weight, the lower the opacity, the more print shows through.

 

Question: What influences the smoothness of paper, and how is the smoothness measured?

Answer: The smoothness of paper is partially determined by the type of fibers used in making the paper. Generally, the shorter the fibers are, the more level or smoother the paper is. Other considerations for making paper smooth include the way the paper is made on the machine, the amount of other products in the paper such as fillers, and the degree to which the sheet is pressed between steel rolls at the end of the paper making process, also known as calendering. The types of coatings and additional calendering, or supercalendering, also add significantly to the smoothness of the paper. The most common method by which to measure smoothness is through an air-leak tester. The smoothness tester machines measure the rate of air flow between a gauge or test plate and the paper surface.