Coated or Uncoated
Paper Stock?
Paper is either coated or uncoated.
Uncoated
paper, which you can find in most paperback
novels, soaks up ink like a sponge. Ink enters the paper
fibers and spreads, causing halftone dots to grow. This
is especially noticeable on newsprint (a kind of uncoated
paper). Halftone screens printed on newsprint are coarse,
and the halftone dots are visible. Photo quality suffers,
but for a throw-away piece like a newspaper or an inexpensive
paperback novel, this is acceptable.
Premium uncoated stock has a smoother
surface (and it may also have some chemical additives),
so the ink is better able to sit on top of the paper surface.
This is called ink holdout. Halftone dots spread less, finer
halftone screens can be used, and, in general, the effect
is much crisper than with low-quality uncoated stock or
newsprint. There is, nevertheless, more bleeding of the
ink into the paper fibers than with coated stock. Therefore,
the printer must compensate by adjusting the halftone screens
so less ink will print, particularly in the mid-tones and
shadows of halftones. For a subdued, ecologically-friendly
look and feel, premium uncoated stock is ideal. You may
see this kind of paper in soft-cover reprints of hard-cover
best sellers.
Coated stock has a
surface sealant (think of varnish on wood). This is made
up of various liquids and clay (and other substances). Coating
allows ink to sit up on top of the surface of the paper
without seeping into the paper fibers. Halftone dots and
type are therefore very crisp and controllable on press.
And, in most cases, coated stock costs more than uncoated
stock.
Within the realm of coated stock, you
have options: matte, dull, satin, and gloss. All give you
varying amounts of surface sheen. Gloss is super-smooth.
It reflects light rays right back at the light source. At
its most extreme level (cast-coated stock), this paper surface
resembles the gloss of patent leather. Its prime attribute
is that it showcases the range of tones from light to dark
in a photo. For instance, you might use a sheet like this
to accentuate the metallic sheen of automotive photos.
Matte is the opposite extreme. It is
still coated, but the texture is rough (on a microscopic
level). Light rays striking this surface are dispersed rather
than reflected directly back at the light source. Even though
it is rougher than gloss, it can give a subdued feel and
refined appearance to a printed sheet.
A good rule of thumb is:
Use a gloss-coated sheet when you’re printing photographs.
Gloss coating makes images pop off the page. Unfortunately,
reading large amounts of text on a gloss-coated sheet tires
your eyes.
Therefore, when you’re producing
a printed product with long passages of text and fewer photos,
choose a matte-coated printing sheet.
A variant on this advice is to choose
a matte-coated sheet for a product with lots of textual
matter and then coat the photos with a gloss varnish. (This
might be appropriate for a coffee-table book incorporating
both text and photos of fine art or architecture.) To add
a gloss varnish in-line (without a second pass on press),
your printer will need a press with an extra printing unit
containing the gloss varnish.
So what about dull and satin?
In my experience, satin is about halfway
between matte and gloss. It often has a little texture and
luster. Not all paper manufacturers include a satin sheet
in their paper lines, and for some paper companies satin
is just another way of saying “not matte/not gloss.”
An option between matte- and satin-coated
paper is a dull-coated sheet. You will see this term more
often than “satin.” I’ve noticed that
(and again, this is somewhat subjective, since the terms
have blurred from paper manufacturer to paper manufacturer,
and there is no single standard for matte, dull, satin,
and gloss), dull seems to be a somewhat more evenly coated
variant of matte. The dull coating seems to be more consistently
spread across the sheet, and the matte coating seems to
be a little more uneven or mottled. Usually, you need a
strong light source to see this. And, as can be expected,
the evenness of the dull coating comes at a price. A dull
sheet often costs a bit more than a comparable matte sheet.
One thing to keep in mind is that all
these terms are fluid from manufacturer to manufacturer.
I’m providing general guidance, a starting point,
if you will. While choosing paper, it is prudent to get
samples from your printer or paper merchant and not rely
solely on verbal descriptions.
Coatings Applied to a Printed Sheet
You start with a coated or uncoated
paper stock. To this you apply ink. After this step, you
have further options for coating the printed sheet, including
varnish, aqueous coating, laminates (liquid, film, and lay-flat),
and UV coating. An entire book could be written about these
options.
Suffice it to say that the same terms
used to describe paper surfaces (matte, dull, satin, and
gloss) describe additional coatings applied to press sheets
(on or off press).
Therefore, to be safe, specify matte,
dull, satin, or gloss paper found in the paper swatch books
provided by the paper mill, your paper merchant, or your
print provider. And when specifying coatings to apply to
these press sheets, either request samples or give your
printer samples showing the final printed effect you desire.
Pulling It All Together
Ink, paper surface coatings like varnish,
and paper surfaces themselves — coated or uncoated
— interact and may cause printing problems. For instance,
you can apply a dull or matte coating to an uncoated sheet
for protection, but a gloss coating would look mottled on
the same sheet. Or, you may find that a certain coating
changes the color of a particular ink it covers. In addition,
you may find that a particular coating will not adhere properly
to certain ink formulations and that address information
applied by ink-jet (a post-press operation) will not adhere
to certain coatings.
All of this can result in your
not getting the printed product you expect. How do you avoid
this? Make it a point to meet with your printer early in
the production process to discuss your choices of paper,
ink, and surface coatings (varnish, UV coating, laminates,
or aqueous coating) and make sure these choices are compatible.
This is one good reason to use an experienced, knowledgeable
print provider with whom you have developed a good working
relationship.
[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.]