Waterless Offset, A.K.A.
Dryography
Conventional offset printing
is based on the chemical properties of oil and water. In
short, they don’t mix. Therefore, with a
little ingenuity, even on a flat surface like an offset
printing plate, you can designate image areas that accept
ink (and transfer the ink to a blanket and then to printing
paper) and non-image areas that repel ink. You do this by
carefully maintaining a precise ink/water balance on press.
This is all well and good, but it presents
some problems. For instance, the water can streak the ink,
and the water limits the line screen you can use to 175
to 200 lpi (image detail is limited).
An offshoot of conventional
offset, called waterless offset or dryography, eliminates
water from the chemical equation. Actually, it
turns the printing process from a chemical balancing act
(ink vs. water) to a mechanical process that can be more
precisely controlled.
Because of this, press operators can
offer the following benefits:
- Brighter colors that are more saturated
and vibrant.
- Halftone line screens upwards of
300 lpi, that allow for consummate detail in the photographs,
smooth blends, fine tints, and a dot pattern almost invisible
to the naked eye.
- Printing devoid of water spots.
- More environmentally-friendly printing,
since there’s no toxic fountain solution maintaining
the ink/water balance and less paper waste since make-readies
are quicker and more accurate.
- The ability to print thicker ink-films
with less dot gain (allowing for more saturated colors
and greater color control).
- Quicker drying times.
Basically, waterless printing
is a winning proposition. According to the Waterless
Printing Association, overall waterless printing costs are
comparable to those for traditional offset. Although waterless
plates and inks cost more than conventional supplies, make-readies
take less time, and there is less waste. Therefore, when
a printer dedicates a press exclusively to waterless offset,
the lowered materials and labor costs offset any other increased
costs.
However, this technology is
very new and most printers probably don’t have it
yet, so you wouldn’t use it for most print jobs.
You might want to use it for a coffee-table art book that
has to be perfect (that is, with images requiring superior
tonal range and detail). Choosing waterless offset would
require you to do a little searching for a vendor offering
this technology.
But what is waterless offset,
really, on a technical level?
Waterless offset uses plates
and ink, like traditional offset lithography, but it employs
no water, no fountain solution to keep ink on the
image areas and away from everything else. To do this, waterless
printers rely on special plates that are aluminum backed
and coated with a photosensitive material and silicone.
When these plates are exposed with a laser and then processed,
the silicone rubber falls away from the image areas, leaving
the aluminum base. Areas not exposed to the laser retain
the silicone coating. In addition, the image areas are slightly
recessed. (Therefore, waterless printing is really less
of a planographic process like conventional offset and more
of a mechanical process like the intaglio printing method
called gravure.) Ink avoids the silicone and collects in
the slightly recessed image areas and then is transferred
to the blanket and from the blanket to the paper (just like
conventional offset).
One variable that must be carefully
controlled in waterless printing is temperature.
On a conventional press, the fountain solution (usually
composed of water and alcohol) is usually chilled, and this
keeps the heat level on press under control. Without water,
the process heats up the ink too quickly. If the ink gets
too hot, it will become less viscous and may adhere to the
silicone. Therefore, temperature must be regulated, and
special inks must be used that are formulated to operate
optimally within the temperature range of the specific press.
In general, waterless
plates can be used for press runs between 10,000
and 600,000 images, depending on the plate manufacturer.
It’s worth mentioning also that conventional presses
can be retrofitted for this technique.
[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.]