An early 20th century printer discovered offset printing by accident. When his printing press ran out of paper, the ink transferred to the rubber impression cylinder. When he added more paper without cleaning the cylinder, the back sides printed with higher quality than the front sides. This was because the flexible rubber reacted well to the paper surface, better transferring the ink. The printer's discovery led his printing house to create the first offset printer, which used an additional blanket cylinder to transfer ink indirectly from the plate to the paper. Offset printing then developed and is now the dominant printing system, though digital printing competition is increasing. Key differences between offset and digital include speed, customization ability, cost effectiveness based on quantity, and color accuracy.

1. In the early 20th century, one
American printer forgot to stop the
press after the paper feeder was
empty. The press continued to run
for several minutes without paper,
which caused the ink to transfer
into the impression cylinder. When
the printer added paper to restart
the press, he had also forgotten to
clean the surface of the impression
cylinder and the first few papers
emerged with print on both sides.
Although the back side was printed
incorrectly, the printer was amazed
by how the quality and sharpness
of the back side exceeded the
correctly-printed front side of each
sheet.
After much discussion with
colleagues, the printer discovered
that the main reason for the
improved print was that the rubber
on the surface of the impression
cylinder was very flexible. The
flexibility of rubber allows it to react
well with the topology of paper
surface, which helps to better
transfer the ink to the surface of the
paper and allowing for a higher
quality print.
The printing house decided to add a
third Blanket Cylinder that would take
the ink (off) of the plate cylinder and
transfer (set) it on to the paper surface,
thus creating the first Offset printer.
Offset printing is an indirect printing
system, where the plate never physically
touches the paper. Offset is often
mistaken for its cousin Litho printing,
although the two are in fact separate
techniques.
Lithography is an even older printing
system, which became immensely
popular almost immediately after its
invention in 1798 by Aloys Senefelder.
In this technique, the artist actually
draws on a specially prepared flat
piece of limestone. It is classified as a
planographic printing system, where
both the printing and non-printing
areas were at the same level, without
any relieved or recessed areas. The
technique relies on the differences
between surface tensions of the ink,
dampening solution, printing and non-
printing areas.
As the technology developed the
printing surface was changed to a
cylinder instead of a flat surface.
Eventually, stone, and later zinc plates
were replaced by aluminium plates,
which allowed print plates to become
easily rounded on the cylinder and are
still in wide use today.
One of the main differences between
Litho and Offset is the fact that Litho
printing is a direct printing method,
where the plate transfers the ink by
directly pressing the paper.
Although there are major differences
between Litho and Offset, the two
printing techniques are connected by
history and by the fact that many in the
printing industry incorrectly tag them
as the same thing. The so-called ‘Litho
Offset’ printing of today is in fact Offset
printing only.
Offset vs. Digital
As the naming controversy continues,
Offset is the dominant printing system
globally with about 55% of the market
share worldwide. Increasingly, Offset
is facing more competition from other
printing techniques, especially digital
printing.
Offset still has many advantages over
digital and other printing technologies,
including high image quality, good
reproduction details with fine resolution
and very sharp halftone dots. Now
that most Offset printers are using
a computer-to-plate system, it has
become easier to prepare Offset plates
and the quality of the final print has been
enhanced. The technique can print on
a wide range of printing materials and
can produce high-quality prints even on
rough paper.
Offset is particularly cost-effective,
because the final ink layer on the printed
material is very thin - only about 1 -2
microns – and the unit cost decreases as
the quantity increases.
While Offset is usually cheaper, digital
printing has many features that allows
a client to get exactly what they want
out of a print, regardless of how specific
their needs may be. On-demand
printing enables a client to indicate just
how, what, where and when their print
is needed before the job starts. A digital
print is uniform from country to country –
for example, an iGen 4 print in Egypt will
look exactly the same as one in England.
Printing with digital takes less time than
with Offset, creates less material waste
and is cheaper for low volume short run
printing.
Perhaps one of the most exciting features
of the digital technique is Variable Data
Printing (VDP). VDP is a form of customisable
personalized printing, where every print and
copy can have adjustable content rather
than the fixed, static printing of all other
conventional printing systems.
Digital Printing or Offset?
We can use the following points in order to help
us make our decision of which technique to
use:
• How quickly is the job needed?
If the job is needed fast or on demand, digital
printing offers much quicker delivery.
• Is there any need for personalization
or customisation?
If the job requires variable content or
personalized prints, digital printing offers the
simplest and most affordable way to customize
prints, with variable contents and data from
one page to the other.
• What is the quantity needed?
Offset printing has prepress costs, therefore
short run prints will have a high unit cost, but as
quantities increase, the unit cost will decrease.
On the other hand, short runs will be much
more cost effective with digital printing, while
larger quantities will be more cost effective
with offset printing.
• What are the materials are you
printing with?
Is there a need for a special paper, finish or
unusual printing surface, or size? The options
are increasing continually for digital printing,
but offset printing still offers the most flexibility.
• Is there a need for special colours?
If you are printing with Pantone colours, Offset
printing will give the best match - although digital
presses are becoming better and better and are
Pantone certified. Offset uses actual Pantone
inks, while digital printing simulates the colour
using a four-colour - sometimes five colour -
system. Because of this, some digital presses may
offer less accurate colour matching with Pantone
colours. With two-colour printing, most digital
presses will cost more to produce the job than
offset.
• Is there a need for proofing?
Since digital printing has a wider larger colour
gamut than Offset, it will offer a more accurate,
economic ISO proofs for offset printing.
One of the best tips for whether to use Offset or
digital is the formula published by Fenton and
Romano in their book, On-Demand Printing: The
revolution in digital customized printing:
(Offset Pre-Run costs – Digital Pre-Run costs)
/ (Digital Running cost – Offset Running costs)
= Breakeven Point
The writers explain that Offset duplicators cost
considerably more for the first copy, but each
additional copy has a lower unit cost than the
digital printer. The break-even point is directly
related to the prepress processes and costs of
the offset.
With all of these facts in hand, it is of your interest
to always evaluate weigh up your costs and your
needs to find the solution for your printing project.
Pól Ó Géibheannaigh
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