Digital Prints

Brightness: Brightness is usually given, if at all, in terms of a rating scale of 1–100, with
100 being the brightest. Keep in mind that some papers achieve a higher brightness by
adding optical brighteners.
Optical Brighteners: Optical brightening agents (OBAs) are commonly used in the
paper, textile, and detergent industries. As the name implies, they’re also added to inkjet
printing papers and coatings to make them whiter and brighter. The way OBAs work
is by absorbing UV radiation and fluorescing (re-emitting as visible light). A common
OBA is titanium dioxide, which is added to the paper’s outer receptor coating. You can
tell if a paper has OBAs added by turning on a portable “black light” in a dark room
and running it over the paper. If OBAs are present, the paper will appear to glow while
a non-optical-brightened paper will appear dark or “optically dead” because no light is
reflected. (This gets more complicated with a 100%-cotton paper that has no OBAs
added to its coating but may have OBAs in the substrate if the original cotton trimmings
contained optical brighteners.)
It’s unclear what long-term effects OBAs have on print permanence. Some believe that
they can possibly contribute to print deterioration, but others disagree, saying first that
not all OBAs are the same, and then that the worst that can happen is a bright white
paper ending up being less white (yellower) as the brightener loses its ability to fluoresce
over time. According to Epson, all its standard papers have optical brighteners to
improve whiteness and to inhibit the yellowing of the paper. Some paper suppliers will
offer a brightened paper and a “natural” unbrightened one as an alternative. Moab’s
Entrada is an example.
Opacity: This becomes an issue with thinner papers, and you see this measurement on
many from Epson plus a few third-party suppliers. Opacity means how opaque the
paper is, or how much “show-through” (how much you can see the image underneath
when stacked) there is. It’s measured with a simple meter; the higher the opacity figure
up to 100, the more opaque the paper. The most common application where opacity
is important is in the making of specialty books and albums.
Dmax: Dmax, the maximum density reading possible at the highest black ink levels,
depends on the type of inks used so this parameter may not be readily available.
However, online discussion lists and other sources sometimes compare the Dmax of
different papers with different inks, so if you can find the numbers (the higher the better),
pay attention, especially if you like deep, rich blacks and shadows. In general, the
smoother the finish, the higher the Dmax reading, all others being equal. Glossy papers
typically have higher Dmax numbers than watercolor papers; dye inks higher than pigments.
Many sophisticated printmakers use devices such as densitometers and spectrophotometers
to calculate their own Dmax measurements with various inksets. See
Table 7.5 for one example.
Chapter 7 ■ Choosing Your Consumables 239