There are two main types of specialty papers used for inkjet printers,
having quite different technologies. There are others, but they are
mainly fine art type papers. I am speaking here of "photo" type papers.
One is Microporous papers, and the other is swellable polymer.
Microporous papers have a ceramic coating on them which is like a glaze,
which allows the ink to pass through the layer. That layer is
transparent and the ink is stored below it usually in a kaolin clay type
substrate. These are instant dry (to the touch) papers. It is true that
the ink takes longer to dry than it appears to when the print comes out
of the printer, but they do not remain wet indefinitely. They probably
dry fully within 24-48 hours at most if left in an unsealed condition.
It is not recommended that prints of this nature be framed or laminated,
or placed in a plastic unbreathable storage envelope prior to they
drying fully. Some people hasten the drying by placing them between
some highly adsorbent paper, like clean (unprinted) newsprint. The main
components that need to come off the ink are glycols which are slower
drying. The alcohol and water evaporate pretty quickly in most
environments unless it is very high relative humidity.
These papers do not hold the ink into the paper as well as others,
because the pores remain open. In some cases of certain dyes, the ink
was found to fade within 24-48 hours if left completely exposed to an
environment where there was a lot of air current. So, with this type of
paper it is best to keep them out of situations that accelerate
evaporation, or agitate the air. Again, placing them in a room with
20-40% relative humidity with a piece of paper laid over the top is a
good way to allow these to cure. These papers are often waterproof, or
nearly so, once dry. However, the surface may be vulnerable to coming
off if tape or something similar is applied taking off the microporous
coating, and changing the texture of the paper, and removing some of the
ink. These papers usually also work with pigmented inks.
Swellable polymer is another paper surface technology. In this case,
the fluid part of the ink liquefies the surface of the paper and causes
it to swell. The ink literally becomes incorporated into the surface of
the paper, and is in part protected by the polymer, which in part covers
the ink as it mixes. These papers usually are slow drying because the
amount of liquid necessary to wet the paper and temporarily dissolve the
surface has to be enough to soften the surface, and then it needs to dry
and reharden. Gelatin is a form of a swellable polymer. Today resins
are often used. These papers, although slow drying, give better
permanence to dye colorant inks. They tend to remain vulnerable to
water and fingerprints, but they usually don't have a surface that comes
off with an adhesive as easily as microporous papers do. These papers
often do not work well with pigment colorant inks, because those inks
have solid matter and resins incorporated, making them less likely to
integrate into the surface properly. Also, the extra solids tend to
make high ink areas look matte, even with a glossy paper.
In general, Epson and Canon use Micropore papers with their printers,
because it has a very shiny surface, and is "instant dry" to the touch.
Epson makes a swellable option called Colorlife which is swellable
polymer, and it is specially designed to improve color permanence of
their dye inks. I believe this paper is made for them by Ilford
Switzerland, and sold as the "non-classic" version.
HP seems to use principally swellable polymer papers, which might
explain why they get better fade resistance with dye inks. Epson offers
their Durabrite and Ultrachromes products as their long life inks.
Art
