What Options are there for Coating a Job?
The two most common reasons for adding
a coating over your printed piece are for protection: to
avoid scuffing the ink, if you have included areas of heavy
ink coverage; and for aesthetic reasons: to draw the reader's
eye to particular items, to add depth and interest to your
printed piece. First consider why you are coating your job.
When making this decision, keep in
mind the following:
- Dried inks show fingerprints
and scuffing, especially in dark solids.
- Press coatings (like varnish)
cost less than bindery (off-press) coatings (like UV coating
and laminates) since bindery coatings are applied over
dry ink at slow speeds. Because the chemicals used in
aqueous coating damage press rollers, this coating is
more expensive for the printer/binder to apply than varnish;
therefore, the extra cost is passed on to the client.
- Varnish is the least effective
way to prevent scuffing, particularly when publications
are multiply shrink-wrapped (as opposed to singly shrink-wrapped)
prior to shipping. Bindery coatings like UV coating and
laminates are far better for protecting loose books in
transit. Even aqueous coating is much stronger than varnish
and can therefore withstand books shifting around in transit
without scuffing.
- All printers can apply varnish,
but not all printers can apply laminates, UV coating,
or aqueous coating.
- You cannot print (ink-jet
or by hand), glue, or foil stamp over coatings, so you
need to leave an uncoated window if you want to do any
of these (coatings should be the final finishing step
on a printed piece).
- You should only varnish coated
stock, or the coating will seep into the paper and be
lost.
- Some coatings deepen the ink color
they cover, yellow with age, and/or discolor white paper.
VARNISH
Varnish is essentially ink without pigment. It requires
its own printing unit on press. It can be wet-trapped (printed
in-line at the same time other inks are laid down), or dry-trapped
(run as an additional pass through the press after the initial
ink coating has dried). The latter often provides a glossier
finish. Varnish comes in gloss, dull, and satin (in-between
dull and gloss), and can be tinted by adding pigment to
the varnish.
From an artistic standpoint, you can
play a dull-varnished portion of the sheet against a portion
without varnish or with a gloss varnish. This contrast can
give emphasis to certain areas and/or give the impression
of depth.
UV COATING
UV Coating is a clear liquid spread over the paper like
ink and then cured instantly with ultraviolet light. It
can be a gloss or dull coating, and can be used as a spot
covering to accent a particular image on the sheet or as
an overall (flood) coating. UV coating gives more protection
and sheen than either varnish or aqueous coating. Since
it is cured with light and not heat, no solvents enter the
atmosphere. However, it is more difficult to recycle than
the other coatings.
UV coating is applied as a separate
finishing operation as a flood coating or (applied by screen
printing) as a spot coating. Keep in mind that this thick
coating may crack when scored or folded.
AQUEOUS COATING
Aqueous coating is more environmentally friendly than UV
coating because it is water based. It has better hold-out
than varnish (it does not seep into the press sheet) and
does not crack or scuff easily. Aqueous does, however, cost
twice as much as varnish.
Since it is applied by an aqueous coating
tower at the delivery end of the press, one can only lay
down a flood aqueous coating, not a localized "spot"
aqueous coating. Aqueous comes in gloss, dull, and satin.
LAMINATE
Laminates come in two types: film and liquid, and can have
a gloss or matte finish. As their name suggests, in one
case a clear plastic film is laid down over the sheet of
paper, and in the other case a clear liquid is spread over
the sheet and dries (or cures) like a varnish. Laminates
protect the sheet from water (including perspiration from
the hands) and are therefore good for coating items like
menus and book covers. For more money, one can even specify
a porous, lay-flat laminate (the interior of which is covered
with numerous "V"-shaped cuts in the plastic that
minimize the "curl" one often sees on paperback
book covers due to moisture seeping into the uncoated side
and causing it to expand). Laminates are slow to apply and
costly but provide a strong, washable surface. They are
the superior choice for protecting loose books in transit.
[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.]