Transcript Printing

Graphic Products
Printing
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Learning objectives
Learning objectives
To learn about:
the different printing methods available
four colour process printing
the printing effects that can be applied to printed
products
quality checks that are performed on printed
products.
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Printing methods
Graphic products can be printed in a variety of different ways.
The designer has to select the printing process that suits their
product best.
This will depend on the length of the print run, the quality
required, the paper or card needed, and the project’s budget.
The designer will choose from the following printing methods:
letterpress
lithography
flexography
gravure
screen printing.
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Printing methods
Letterpress
Letterpress is one of the oldest forms of industrial printing.
Letterpress is known as a relief printing method, because the
printing plate is not flat.
A printing plate is prepared with the image to be printed raised
above the surface of the plate, standing proud
of the non-printing area.
The raised surface is coated with ink
and is then pressed onto the paper.
It is an expensive process, as the
plate has to be specially made and
high quality paper is needed. It is used
for high quality books and stationary.
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Printing methods
Lithography
Lithography is the most
commonly used process in the
printing industry.
The image is transferred onto
the completely flat printing plate
photographically, using UV light.
The plate is washed in a chemical
that makes the image area attractive to the oil-based ink.
The non-image area is dampened with water to repel the ink.
Lithography is used for medium to large print runs because the
set-up costs are high.
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Printing methods
Flexography
Flexography is very similar to
letterpress as it uses a relief
plate. As the name suggests, the
relief plate is made from a flexible
material, like rubber.
It is used to print on
unconventional materials, like
polythene for packaging.
Flexography is ideal for these
surfaces, because the ink is mixed
with a solvent that evaporates,
causing the ink to dry quickly.
Flexography is used on carrier bags and some wallpapers.
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Printing methods
Gravure
Gravure is used to produce high quality photographic images.
It is very good for reproducing fine detail. However, gravure is
a very costly process due to the skill needed to manufacture
the printing plate.
It is the opposite to letterpress –
the printing areas are in fact
lower then the non-printing
areas. The image is engraved
onto a copper plate, creating
cells that are filled with a spirit
based ink. The paper is pressed
against these cells to produce
the image. The ink evaporates
quickly once printed.
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Printing methods
Screen printing
Screen printing is completely different to any other printing
method. It works by forcing ink through a stencil. The stencil
shape reflects the image to be printed. The stencil can be
made of paper or card and is supported by a fine mesh.
The ink is spread over the mesh using
a spreader, and then forced through
the mesh onto the surface to be
printed. Stencils can be made fairly
simply, but to create more complex
images, a photographic stencil is
required. These have to be made by
a professional or using a computer.
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Printing methods
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Die cutting and folding
Guillotines can be
used to cut straight
edges on batches of
card and paper. Die
cutting is used when
the shape is irregular.
A blade similar to that of a cookie cutter is made, and the
design is stamped out. This can be done by hand or using a
hydraulic press.
Folds are created in a similar way, except that the blade
does not cut all the way through – it creates a crease instead.
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Printing effects
You can add interest and impact to a graphic product by
adding a printing effect. There are lots of printing techniques to
choose from, but they can restrict your choice of materials and
add to the final cost.
The designer can choose from the following printing effects:
Spirit Varnishing
UV Varnishing
Embossing
Laminating
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Printing effects
Varnishing
Applying varnish to a product
has two main functions:
to protect the product
to make the product look better.
Varnishing is done after printing but before any cutting,
folding or trimming.
There are several different types of varnishing. Oil-based
and water-based varnishes are sometimes used, but the
most important types of varnishing are spirit varnishing
and ultraviolet varnishing.
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Printing effects
Spirit varnishing
Spirit varnishing involves applying a spirit-based
coating to the product to produce a high-shine finish.
It is relatively cheap, but the ink must be completely
dry before the varnish is added, making the
manufacturing time longer.
UV varnishing
Ultraviolet varnishing involves applying a thin coating of
liquid plastic, and then hardening it using UV radiation.
It gives a tougher, glossier finish than spirit-based
varnishing, but is more expensive. It cannot be added
until the printing ink is completely dry.
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Printing effects
Laminating
(or encapsulating)
produces a tough,
high gloss finish.
The image is sealed
between two layers of
plastic. It is twice as
expensive as varnishing,
but the end result is of a
lot better quality.
HOT
LAMINATE
COLD
LAMINATE
Lamination is used for products like menus
that need to be easily wiped clean.
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Printing effects
Embossing is when a portion of the surface is raised above
the surrounding area.
It is used for two reasons:
visual impact
add texture
The required
shape is pressed
into the work
using a steel die.
Embossing can give an
expensive, high quality feel.
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Printing effects
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Process colours
To reproduce a full colour image or document, commercial
printing companies use what is called ‘four colour process
printing’.
The four colours are called the ‘process colours’. They are
overlaid to produce the full range of colours. The process
colours are:
Cyan
Magenta
Yellow
Black
These colours are
known as CMYK.
Black is represented by
the letter K so it is not
confused with blue.
The image is separated into the four process colours, and a
separate printing plate is produced for each. This is known as
‘colour separation’.
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Process colours
This image shows the colour separation for the picture in
the top left hand corner.
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Quality checks
Quality is essential in all products – printed products are no
exception. When a document or item is printed, a series of
marks are created that allow manufacturers to check that the
printing has been done correctly:
Registration marks
These marks allow printers to
check alignment. If the colour
plates are aligned properly,
the mark will appear black.
Colour blocks
Allow you to check the
colour for correct tone
and equal density.
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Plenary
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Key points
Key points
There are many different printing methods
available, including letterpress, lithography,
flexography, gravure and screen printing.
Die cutters and creasing bars are used to cut
out shapes and create folds accurately.
You can add interest and texture to graphic
products by varnishing, laminating or
embossing them.
Commercial printers usually use four colour
process printing, which involves colour
separation.
Registration marks and colour blocks are used
to check print quality.
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