Paper Weight & Size -- When is 80# NOT 80#?

Why doesn't 80# cover stock feel anything like 80# text stock? If you feel both sheets between your thumb and index finger, you'll find that the cover stock is stiffer and more resistant to bending. And why doesn't a ream (500 sheets) of 8.5" x 11" cover stock weigh the same as a ream of 8.5" x 11" text stock?

Or, to confuse matters further, if the Post Office requires business reply cards (postcards) to be at least 7pt. in thickness (0.007"), how does this measurement relate to the above-mentioned cover weight and text weight?

First of all, 500 sheets of 80# cover stock do actually weigh 80#, just as 500 sheets of 80# text stock weigh 80#. The trick is that the 8.5" x 11" cover stock noted above was cut down from a 20" x 26" "basic size" sheet of cover stock. The basis weight of 500 sheets of cover stock at the basic size is 80#. Text stock is cut from a larger sheet (25" x 38"). Therefore, 500 sheets of text stock at the basic size also weigh 80#.

What does this mean for all the different categories of paper, and what is M weight, then? To start with the simpler question, the M weight is the weight of 1,000 sheets of a particular stock. Paper merchants often quote the price of paper as a per-M cost rather than a per-ream cost.

See the glossary in the next section to better understand the more complex question of basic sizes for different grades of paper.

Are different sizes produced beyond these basic sizes? Yes. For example, a printer might order a ream of 28" x 40" text stock for a particular job (perhaps to allow for a greater number of brochures to fit on the flat sheet with room for color bars).

How do sizes of different grades relate to one another? This is complex and inexact. I was once told that 55# cover was comparable to 105# text, and that 67# Vellum Bristol was comparable to 7pt. postcard stock. And 20# bond, or 20# laser paper, is "about" the same as 50# text (while 24# bond, or 24# laser paper, is "about" the same as 60# text; and 28# bond, or 28# laser paper, is "about" the same as 70# text).

This is not a rule of thumb, since some papers (high-bulk stock for instance) are actually thicker, when checked with a micrometer, than the same weight of a stock that is not high bulk. But it is a starting point for discussion with a printer or paper merchant.

When in doubt, talk with your printer and measure the paper's thickness with a micrometer. Also, learn to use a paper swatch book, which will show you the size of the parent sheets and the paper grain direction. Even more useful than any of these metrics, it will show you what a particular sheet feels like.

If you're printing business reply cards, ask your paper merchant or printer if a sheet "mics" (as in micrometer) to 7pt. This is the legal thickness for a postcard as specified by the US Postal Service.

If you're printing a book, consider how the cover and text sheets will work together. Is the cover stock too heavy or too light? If you pick an 80# cover stock to pair with an 80# text stock -- for an annual report, for instance -- you should be fine. On the other hand, if you're printing a 300-page paperback book, you might want to match a 10pt. cover with 50# text. A lighter cover might feel flimsy, while 80# text would make the thickness of the book unwieldy, and the weight of the book might require excessive postage.

Choose a stock as you would a fine fabric, by its feel between your fingers. When in doubt, ask your printer or paper merchant to create a paper dummy using the weight and grade you plan to spec for the final printed product.

A BRIEF PAPER GLOSSARY

• Bond (17" x 22"): writing papers, including ledger, that accept ink readily and can be erased
• Coated (25" x 38"): book paper with a clay coating ensuring smoothness (dull, satin, gloss, matte)
• Text (25" x 38"): uncoated book paper (often of an interesting color) used for announcements and the like
• Offset (25" x 38"): uncoated book paper treated with sizing to resist moisture
• Opaque (25" x 38"): uncoated book paper treated to be less transparent
• Cover (20" x 26"): coated and uncoated; used for book covers, brochures, etc.
• Mill Bristol (22.5" x 28.5" and 22.5" x 35"): a board grade receptive to folding, embossing, and stamping
• Index Bristol (25.5" x 30.5"): an inexpensive, stiff board grade, with a harder surface than Mill Bristol
• Tag (24" x 36"): water resistant and foldable, used for tags
• Newsprint (24" x 36"): used for printing newspapers; highly acidic, degrades quickly
• Digital: for copiers and ink-jet and laser printers, as well as high-end digital presses like Xeikon and Indigo

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[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]