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Understanding and Specifying Paper Thickness
Which paper is thicker: 28-pound (28#) bond/writing paper or 50# uncoated offset stock? It may seem counterintuitive, but the 28# bond is thicker!
Why? Paper is measured either in pounds per 500 sheets (one ream of paper) or in pounds per 1,000 sheets (see below) of a standard size of sheet based on the group or category of papers being graded. The different types of grades are Bond, Book, Text, Cover etc. Each group of the grade of paper is assigned a standard size that all weights are referred to. The basics of this standard are as follows:
Bond has a standard size of 17 x 22" and this is the size that is measured for 500 sheets. If 500 sheets of this size weigh 20lbs., then the paper is classified as a 20lb. bond. Heavier and lighter stocks will obviously be thicker or thinner than the 20lb. Therefore 16lb. Bond or 24lb. Bond will be the variations on this.
Now the confusion... the weight of 500 sheets of the standard sheet size (also known as the basis size) is commonly known as the paper's basis weight and is always noted as a weight in lbs.
This can be confusing! Here's why.
A sheet size different than the above is calculated as a fraction or multiple of the basis weight and is normally noted for 1,000 sheets rather than 500. The weight thus calculated of the acutal sheet size is always noted in weight per thousand (M in roman numerals) and therefore said to be 19 X 25" - 100M meaning that 1,000 sheets of 19 x 25" will weigh 100 lbs.
If 500 sheets of Bond paper (17 x 22 inches) weigh 20 lbs, then a ream of paper cut to Letter size will be labeled as 20 lb.
Writing is a grade similar to bond, but made with a shorter fiber, yielding a softer sheet which can be made with a variety of finishes and which accepts ink more readily. Writing is generally more expensive than bond and is used for higher end applications like company stationery. Some bond and writing papers have distinctive watermarks in the sheet.
Uncoated offset is made specifically for the rigors of commercial offset presses and is often used for the same applications as bond.
The basis size of bond/writing papers is 17 x 22", whereas offset papers is 25 x 38".
Equivalent bond/writing and offset weights:
The basis size of Book papers is 25 x 38"
The basis size of Text papers is 25 x 38"
The basis size of Cover papers is 20" x 26"
To determine equivalent thickness, use the chart below to convert between paper types.
|Weight and Thickness Equivalents for Paper Stocks|
|Coated Text Gloss|
|Coated Text Dull|
|Coated Cover Gloss|
|Coated Cover Dull|