What is Flexography?
When you pick up a frozen dinner in
the grocery store or wrap a birthday present, you are most
likely handling a product printed via the flexographic process.
In contrast to offset printing, which
is a planographic printing technique in which the image-
and non-image areas of a print job are on the same level
on a printing plate, flexography is a relief printing process.
That is, the image area is raised above
the non-image area. Cutting a relief image in a linoleum
block -- or even in a potato, as many of us did as children
-- and then pressing the block (or potato) into ink and
then onto paper approximates the flexographic process.
The inks can be either water-based
or solvent-based, and both sheetfed and web presses can
be built for flexographic printing.
Unlike offset printing, flexography
does not transfer the image from the printing plate to a
blanket and then to the paper. Instead, flexography, like
letterpress, transfers the ink directly from the plate to
the paper. But whereas letterpress plates are made of metal,
flexographic plates are made from a more flexible substance
such as rubber or photopolymer materials.
Flexography is most often used for
printed products such as envelopes, bags, tags, wrapping
paper, corrugated boxes, milk cartons, newspapers, packaging,
pressure-sensitive labels, and flexible films.
Why is this process so useful for printing
these specific items?
First of all, the ink used in flexography
dries very quickly. This makes it perfect for non-porous
materials such as plastics and foils. It is also ideal for
printing on packaging materials, since the soft rubber plates
don’t crush thick, compressible materials like corrugated
What is Screen Printing?
Like flexography, silkscreen (or serigraphy)
has wide-scale commercial printing applications. It is most
useful for apparel, signage, and such specialty products
as looseleaf binders. It is, however, better suited to short
runs than flexography, which is better suited to long runs
of single items. Screen printing can also print on substrates
of any thickness and size (a huge banner, for example),
whereas flexography is limited to certain sizes.
Screens today are made of nylon, Dacron,
and even stainless steel, and the stencils that allow certain
portions of the image to print and prevent other portions
from printing are produced either mechanically or photomechanically.
Once exclusively a manual process,
silkscreen has been mechanized through the use of rotary
screen presses. In the past, the drying time of the thick
layer of ink limited the usefulness of this technique, but
now drying times have been shortened through the use of
inks cured with ultraviolet radiation.
Screen printing can lay down very thick
ink deposits onto almost any surface, including fabric,
plastic, metal, paper, leather, wood, glass, ceramic, or
even printed circuit boards used in electronics manufacturing.
A screen-printed product can be recognized by its thick,
raised ink and, in some cases, even by an impression of
the mesh screen on the ink.
Screen printing can be used to print
on almost any size or shape of material. Using this process,
one can vary the thickness of the ink film and use a high
quantity of pigment in the ink, allowing for brilliant colors
and durable products that can tolerate everything from harsh
weather (signage) to laundering (silk-screened shirts).
Equipment costs are also comparatively modest.
[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.]