Specifying Paper for Printing
The more you know about the characteristics
of paper, the better able you will be to save money when
specifying paper for your printing jobs. In fact, if you
specify the qualities you require in your paper, rather
than a specific name brand, your printer may be able to
offer several acceptable options.
Each paper stock possesses the following
characteristics: surface texture, brightness, color, whiteness
(if you specify a white sheet), opacity, grain direction,
weight, bulk, caliper, and size.
Uncoated and coated paper have different
surface textures. In the papermaking process, uncoated stock
has been compressed between metal rollers (calendared) only
to a limited degree, yielding vellum, antique, wove, and
smooth surfaces (from rough to smooth, depending on the
amount of calendaring). Coated paper varies from roughest
(matte) to smoother (dull) to smoothest (gloss), also depending
on the amount of calendaring. Papermaking machines can even
impress such textures as "linen" and "canvas"
on paper. The smoother the paper, the better the "holdout"
(the better the ink sits up on the surface of the paper
rather than being absorbed into the fibers).
Brightness refers to the amount of
light a sheet reflects (0 to 100 percent, with a crisp white
sheet often exceeding 90 percent). Whiteness refers to the
color of the reflected light (either yellow-white or blue-white,
i.e., warm or cool). Brightness and whiteness affect readability
(too much light tires your eyes when reading long blocks
of text) and the crispness of photos (too little light reflected
back makes photos seem dark or muddy).
Paper color is tricky. It changes the
color of the ink, so always request printed samples. Colored
stock is also more expensive than white stock because of
the dyes used and because it is less in demand. Off-whites,
referred to as cream, ivory, etc., are a good option for
some jobs, but the names differ from paper mill to paper
mill, and the appearance will change among paper batches
produced at different times.
Opacity determines show-through. A
sheet with high opacity will prevent solids, screens, and
halftones from being visible through the opposite side of
the sheet, which could otherwise be quite distracting. Colored
sheets are usually more opaque than white sheets. This quality
is rated on a 1 to 100 scale. Most sheets fall in the 80
to high 90 range.
Weight is based on the size of 500
sheets (a ream) of paper. A ream of 80# cover, measured
at 20" x 26", weighs 80 pounds. The same paper
in text weight still weighs 80 pounds but the sheet size
is different: 25" x 38". It is therefore a thinner
sheet. Of course these sheets can be cut to a smaller size.
This is just a convention for precisely describing different
grades of paper, such as bond, offset, etc. Another scale
is in points (thousandths of an inch). You might, for instance,
specify a cover for a perfect-bound book as a 10 pt. sheet.
To be safe, always ask for samples.
Caliper is the thickness of paper when
measured with a micrometer. It is related to bulk, which
is a relative measure of the thickness as related to the
basis weight of a sheet. For instance, 75# Hi-Bulk is thick
enough to pass US Postal regulations for reply card thickness
(7 pt.). Another sheet of this weight might have been further
calendared and its fibers compressed more, yielding a thinner
sheet. Lower bulk reduces opacity. Higher bulk will increase
the overall thickness of a book. Therefore, it helps to
know a paper's measure in pages per inch (caliper).
Finally, grain direction refers to
the direction the fibers of a sheet have aligned during
the papermaking process. In grain long papers, the fibers
run parallel to the length of the sheet. In grain short
paper the opposite is true. Paper folds better parallel
to the grain direction, but is stronger against the grain.
Also, paper can expand against the grain when exposed to
a press' dampening solution or moisture in the air. Therefore,
to maintain tight register a job on this paper would be
run grain long.
All of these qualities affect the runnability
and printability of the paper, as well as its appearance,
so listen to your printer's advice. However, don't hesitate
to request samples, both printed and unprinted, of any sheet
suggested by your printer. Only by actually seeing a printed
sheet can you know whether a particular paper will work
for your own job.
[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.]