To get the best out of an ink jet photo print, you need to increase the number of layers and introduce specialist coatings to handle particular aspects of the printing process. A modern photo paper may well have seven or more different layers to provide, among other things: a gloss finish, protection from UV and ozone, absorption of the carrier, improved drying time and resistance to sticking, one sheet on another.
Within the general category of photo papers, there are two distinct types: swell able and porous. Swell able coatings do actually swell. The surface coating gets thicker as the carrier and the ink soaks into it. The idea is that the ink is sucked into the paper, which gives it extra protection from light and gas attack. As you might guess, if you took in the difference between dyes and pigments, swell able paper is best suited to dye-based inks, but even with dyes, you shouldn’t expect prints to be dry enough to handle safely until about an hour after printing. They can take over a day to dry completely.
Porous paper, on the other hand, works better with pigmented ink, as it’s designed to let the ink carrier soak into the paper and leave its payload of pigment on the surface. Because most of the liquid carrier soaks away fast into the porous sub-layers, images printed on porous paper are usually touch dry within a second or so and completely dry in a few hours. Some photo papers also have deliberately rough back-coatings. This is so that when you’re printing several photographs in a batch, each new print to leave the printer doesn’t stick to the one below in the output tray, which may not have finished drying.
As with most technologies, things are not cut and dried and by varying the constituents of the different layers in a photo paper you can make a sheet which is supremely good at working with dye-based inks or one which is ideal for pigments. In between, it’s possible to make a paper which is better than reasonable for both and this is why you’ll find papers which claim to be suitable for all the major brands of ink jet printer, even when some traditionally use dyes, while others rely on pigments. It doesn’t invalidate what the ink and paper makers tell you, but simply proves that compromise still has benefits.
May 20