Understand Which Different Types of Paper
Learn What "Paper Weight Means"

Basis Paper: All you want to know about paper weight

Basis Paper: All you want to know about paper weight

• What does 20# copy bond paper mean? Find out
  
  
• What does 60# offset paper mean?
  
  
• If you closed your eyes and touched a 20# and a 60# paper, would you be able to tell the the difference between both?
  
  
• How is 50# offset paper any different in thickness than 20# copy bond paper? Learn the tricks!
  
  
• What is the meaning of the symbol "# "or the word "pounds" in the printing industry?. Click to read
  
  
• Coated (Glossy or Dull) Paper. Click to read
  
  
• Paper Manufacturers. Click to read
  
  
• Weight of Paper in USA. Very interesting!
  

International System to Determine the Weight of Paper:

• International Metric System: Countries adhering to the metric system or IS (US does not), use the grammage or paper density to determine the paper weight
  It usually reads something like xx grams/square meter (g/m2) somtimes refered to as "gsm" which is an easy way to know which paper is "heavier or lighter" than any other.
  
  Printing paper is generally considered so when it weights between 60 g/m2 and 120 g/m2. Anything heavier than 160 g/m2 is considered card.
  

How to determine Paper Weight in USA

• We use a system known as Basis Weight to describe the weight of paper, which is not a very direct method and it is not intuitive as the ISO system is. (the numbers mean less by themselves; they require additional information to indicate which paper is thicker, and so on)

Paper rolls are then extended flat, cut to size and piled in reams. As consumers, we are familiar with letter-size reams for our laser or color printing done at home or at our work office.

So far we know:

1. Paper is manufactured in rolls of different widths and qualities

2. The roll is extended flat and transformed into big reams of what's known as Parent Size Reams which as you could see on the image above, are really big.

3. Parent Size Reams will be later cut to final size (example: 81/2"x11", 81/2"x14",11"x17", etc).

If you take 500 parent-size sheets of the type of paper that you are working with and put them on a scale, you'll get a certain weight, measured in avoirdupois pounds (16 ounces per pound). A table bellow shows what the parent sizes are for different types of papers. (Go to table)

The weight of those 500 sheets turn out to be, for example:
- 20# bond paper (This means that 500 sheets of parent size sheets, (the table bellow shows that that particular size is 17"x22") will weight 20 lbs on a scale.

- 60# offset paper (this means that 500 sheets of the parent size sheets for offset paper made with this particular thickness weights 60#. Please notice that the parent size sheet for offset
paper is 25"x38" as opposed to 17"x22" for bond paper.

Conclusions:

1. You can only compare "the pounds" (or the weight) between the same type of paper.
   In that case, the higher the value in pounds, the heavier the paper. Weight comparisons without the paper type reference is meaningless (pretty much like comparing pears to apples)
   
   
2. Comparing the number of pounds of different types of paper is like comparing apples to oranges.
   You cannot should never compare 100# coated text (belonging to the book or text group) with 100# cover (that belongs to the cover group)
   

Coated Paper: Glossy, Dull or Matte Finishes

Description: Coated paper is paper that has been coated by a clay compound to impart certain qualities to the paper, including weight and surface gloss, smoothness or ink absorbency. Kaolinite and calcium carbonate are most often used for coating papers used in commercial printing.

During the manufacturing process, the wet pulp that makes the paper goes through superficial smoothing steps that include calendering rolls made of smooth iron to polish the paper and give it a very smooth finish, press rolls and blankets. If the rolls are mirror-finished, the paper becomes glossy. A different set of rolls will create a coated surface that is dull (slightly glossy) or matte (non-glossy, flat looking paper).

• The quality of paper used for coated papers is FREESHEET PAPER, which is free of groundwood pulp, whiter and used for most commercial purposes (known as 3 grade).

• The base paper is made first, then put through a "bath" of clay coating or coated while running on a machine, with a blade and calender rollers smoothing out the coating on the paper.

• The clay coating often accounts for as much as half the weight of the paper.

• The quality of the clay used determines the brightness of the paper, the printability and the mechanical properties (resistance to tear, shear, etc) as well.

Cost: Because of the complexity of the finishing and the proportion
of clay applied vs the amount of freesheet paper used:

• Glossy paper is less expensive (and lighter) than dull or matte versions.

Coated paper has the following two main characteristics:

• Visually appealing shades

• Excellent surface smoothness & printability

Uncoated Offset Paper

Uncoated Paper is designed to generally run in offset presses and is a non-coated sheet of #50 or 60#. Also- return card offset stock is usually run on a 75# uncoated stock to meet postal requirements.

Uncoated sheets used to be made predominantly in an "acid" process. But librarians and others began to realize several decades ago that the acidic quality of the paper limited its life span. Many papers are now made in an alkaline process, which results in an acid-free, archival quality paper.

Uncoated papers have a slightly fibrous surface rather than a clay coating

Finishes most frequently are smooth or vellum, but may also include slight patterning, as in laid or linen finishes

Opaque Paper

• A higher-quality offset with higher opacity (less show-through)

• More expensive than commodity offset

• "Satin," "Film Coat," and "Thin Coat" finishes refer to a very light clay coating, plus polishing to a very smooth, tight finish, also often used for printing such as manuals.

• Almost all opaque papers contain recycled paper in rates that go from 10% to 100% on totally recycled papers

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