Modern printing methods such as laser and ink-
jet printing are known as digital printing. Digital
printing consists of an image being sent directly
to the printer using digital files such as PDFs and
those from graphics software such as Illustrator
and InDesign. This eliminates the need for printing
plates, commonly used in offset printing, which
can save money and time. Prepress Plating Decisions Other Plate Types
A print job that prints only in black ink requires only
one plate. A print job that prints in red and black ink
requires two plates. In general, the more plates that
are needed to print a job, the higher the price. In screen printing, the screen is the equivalent of
the printing plate. It can be created manually or
photochemically and is usually a porous fabric or
stainless steel mesh stretched over a frame.
Offset Printing Process In some cases, there may be more than four plates
— if a logo must appear in a certain Pantone color,
for example, or if a metallic ink is used in addition to
full-color images.
Things become more complicated when color
photos are involved. Offset printing requires the
While offset printing still often results in slightly
separation of colored images into four ink colors
better quality prints, digital methods are being
— cyan, magenta, yellow and black. The CMYK
worked on at a fast rate to improve quality and lower files eventually become four plates that run on the
costs.
printing press at the same time on four cylinders.
CMYK is different from the RGB (red, green, blue)
Although state-of-the-art commercial printing
color model you see on your computer screen. The
companies are moving to digital printing, many
digital files for every print job are examined and
printers still use the tried-and-true offset printing
method that has been the standard in commercial adjusted to minimize the number of plates needed
to print the project and to convert color images or
printing for more than a century.
complicated files to only CYMK.
Offset lithography — one of the most common
way to print ink on paper — uses printing plates to
transfer an image to paper or other substrates. The
plates are usually made of a thin sheet of metal, but
in some instances, plates may be plastic, rubber
or paper. Metal plates are more expensive than
paper or other plates, but they last longer, produce
high-quality images on paper and have greater
accuracy than plates made of other materials.
Paper plates are usually suitable only for short print
runs without close or touching colors that require
trapping. Plan your design so that paper plates can
be used effectively if you want to save money. Not all
commercial printers offer this option.
Depending on the size of the finished printed
product, several copies of the file may be printed
on a large sheet of paper and then trimmed to
size afterward. When a job prints on both sides of
the sheet of paper, the prepress department may
impose the image to print all fronts on one plate
and all backs on another, an imposition known
as sheetwise, or with both the front and back on
An image is put on the printing plates using a
photomechanical or photochemical process during a single plate in a work-and-turn or work-and-
tumble layout. Of these, sheetwise is usually the
a stage of production known as prepress — one
most expensive because it takes double the number
plate for each color ink to be printed.
of plates. Depending on the size of the project, the
Printing plates are attached to the plate cylinders
number of inks and the size of the sheet of paper,
on the printing press. Ink and water are applied
the prepress department chooses the most efficient
to rollers and then transferred to an intermediary
way to impose the project on the plates.
cylinder (blanket) and then to the plate, where the
ink clings only to the imaged areas of the plate.
Then the ink transfers to the paper.
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Lucid Motif Graphic Industry