Paper coatings may be incorporated during the papermaking or may be
coated as part of the printing process. Clay coatings applied to the
paper during manufacture can add gloss and strength to the paper. Color
coatings can be applied, such as whitewashing kraft paper. There are
also coatings to improve grease or water resistance.
Coatings applied during the printing process can either be applied
after the ink is dry or over wet ink. Dry application can give a more
stark effect; wet application provides more subtle effects. Three common
print-process coatings are overprint varnish, aqueous coating, and
ultraviolet (UV) coating.
Overprint varnish is solvent-based like some inks. Like any varnish,
it can be made as gloss, satin, or flat. The overprint varnish can
be coated all over the page or used to highlight select areas. By using
different varnish finishes on the same page, such as gloss on the subject
and flat on the background, a three-dimension effect can be created.
A varnish coating on a print product protects it from wear. A disadvantage
is the volatile organic compounds (VOCs) contained in the solvents,
which require special safety measures during the print run.
Aqueous coatings (water-based) are applied during the press
run and can be used
in the same ways as overprint varnish. There are few or no VOC problems
with aqueous coatings.
Ultra-violet (UV) coatings are cured (hardened) with UV light. The
curing is almost instant, so other processes, such as die-cutting,
can be done in the same press run.
Contact Wood Printing Service for help and detailed information about
paper coatings. Learn ways to use them to make
your next print project better.
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