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| HISTORY OF SCREEN PRINTING |
Traditionally,
silk was used in the process. Currently, synthetic threads are commonly used in
the screen printing process. The most popular mesh in general use is made of
polyester. There are special-use mesh materials of nylon and stainless steel
available for the screen-printer. There are also different types of mesh sizes
which will determine the outcome and look of the finished design on the
material.
The technique is
used not only for garment printing but for printing on many other substances,
including decals, clock and watch faces, balloons, and many other products.
Advanced uses include laying down conductors and resistors in multi-layer
circuits using thin ceramic layers as the substrate.
HISTORY
The poster shop at Heart Mountain War Relocation Center was
operated by Japanese-American internees who used the silkscreen method to print
information for the entire center (January 1943)
ORIGINS
Screen printing
first appeared in a recognizable form in China during the Song
Dynasty (960 - 1279 AD). It was then adopted by other Asian countries
like Japan and was further created using newer methods.
ADOPTION IN THE
WEST
Screen printing
was largely introduced to Western Europe from Asia sometime in the late 18th
century, but did not gain large acceptance or use in Europe until silk mesh was
more available for trade from the East and a profitable outlet for the medium
discovered.
Early in the
1910s, several printers experimenting with photo-reactive chemicals used the
well-known actinic light-activated cross-linking or hardening traits of
potassium, sodium, or ammonium chromate and dichromate chemicals with
glues and gelatin compounds. Roy Beck, Charles Peter, and Edward Owens
studied and experimented with chromic acid salt-sensitized emulsions for
photo-reactive stencils. This trio of developers would prove to revolutionize
the commercial screen printing industry by introducing photo-imaged stencils to
the industry, though the acceptance of this method would take many years.
Commercial screen printing now uses sensitizers far safer and less toxic than
bichromates. Currently, there are large selections of pre-sensitized and
"user-mixed" sensitized emulsion chemicals for creating
photo-reactive stencils.
A group of
artists who later formed the National Serigraph Society, including WPA artists Max
Arthur Cohn, Anthony Velonis, and Hyman Warsager, coined the word
"serigraphy" in the 1930s to differentiate the artistic application
of screen printing from the industrial use of the process. "Serigraphy"
is a compound word formed from the Latin "sēricum" (silk) and Greek
"graphein" (to write or draw).
Historians of the
New York WPA poster shop give sole credit to Anthony Velonis for establishing
Silkscreen methods used there, a reputation bolstered by the publication of his
1937 booklet Technical Problems of the Artist: Technique of the
Silkscreen Process. Guido Lengweiler has corrected this
misunderstanding in his book, A History of Screen Printing,
published in English in 2016. Outgrowths of these WPA poster shops, at least
two New York City studios in wartime started decorating ceramic tiles with fire-on
underglaze applied by silkscreen starting as early as 1939: Esteban Soriano
and Harold Ambellan's Designed Tiles.
The Printers'
National Environmental Assistance Center says, "Screen printing is
arguably the most versatile of all printing processes. Since rudimentary screen
printing materials are so affordable and readily available, it has been used
frequently in underground settings and subcultures, and the
non-professional look of such DIY culture screen prints has become a
significant cultural aesthetic seen on movie posters, record album covers,
flyers, shirts, commercial fonts in advertising, in artwork and elsewhere.
THE 1960S TO PERCENT
Credit is given
to the artist Andy Warhol for popularising screen printing as an
artistic technique. Warhol's silkscreens include his 1962 Marilyn Diptych,
which is a portrait of the actress Marilyn Monroe printed in bold
colors. Warhol was supported in his production by master screen printer Michel
Caza, a founding member of Fespa.
Sister Mary
Corita Kent gained international fame for her vibrant serigraphs during
the 1960s and 1970s. Her works were rainbow colored, contained words that were
both political and fostered peace and love, and caring.
American
entrepreneur, artist, and inventor Michael Vasilantone started to use, develop,
and sell a rotatable multicolor garment screen printing machine in 1960.
Vasilantone later filed for a patent on his invention in 1967 granted
number 3,427,964 on 18 February 1969. The original machine was
manufactured to print logos and team information on bowling garments but was soon directed to the new fad of printing on T-shirts. The Vasilantone
patent was licensed by multiple manufacturers and the resulting production and
boom in printed T-shirts made this garment screen printing
machine popular. Screen printing on garments currently accounts for over half
of the screen printing activity in the United States.
Graphic
screen-printing is widely used today to create mass- or large-batch-produced
graphics, such as posters or display stands. Full-colour prints can be created
by printing in CMYK (cyan, magenta, yellow and black).
Screen printing
lends itself well to printing on canvas. Andy Warhol, Arthur Okamura, Robert
Rauschenberg, Roy Lichtenstein, Harry Gottlieb, and many other
artists have used screen printing as an expression of creativity and artistic
vision.
Another
variation, digital hybrid screen printing, is a union between analog screen
printing and traditional digital direct-to-garment printing, two of the most
common textile embellishment technologies in use today. Essentially, digital hybrid
screen printing is an automatic screen-printing press with a CMYK digital
enhancement located on one of the screen print stations. Digital hybrid screen
printing is capable of variable data options, creating endless customizations,
with the added ability of screen print-specific techniques.
METHOD
Screen printers use a silkscreen, a squeegee, and hinge clamps to screen print their designs. The ink is forced through the mesh using the rubber squeegee, and the hinge clamps keep the screen in place for easy registration
A. Ink. B. Squeegee. C. Image. D. Photo-emulsion. E. Screen.
F. Printed image
Different samples of the printed image
A screen is made
of a piece of mesh stretched over a frame. The mesh could be made of a synthetic
polymer, such as nylon, and a finer and smaller aperture for the mesh
would be utilized for a design that requires a higher and more delicate degree
of detail. For the mesh to be effective, it must be mounted on a frame and it
must be under tension. The frame which holds the mesh could be made of diverse
materials, such as wood or aluminum, depending on the sophistication of the
machine or the artisan procedure. The tension of the mesh may be checked by
using a tensiometer; a common unit for the measurement of the tension of the
mesh is Newton per centimeter (N/cm).
How to screen print one image
How to screen print with multiple layers using CMYK
A stencil is
formed by blocking off parts of the screen in the negative image of the design
to be printed; that is, the open spaces are where the ink will appear on the
substrate.
Before printing
occurs, the frame and screen must undergo the pre-press process, in which an
emulsion is 'scooped' across the mesh. Once this emulsion has dried, it is
selectively exposed to ultra-violet light, through a film printed with the
required design. This hardens the emulsion in the exposed areas but leaves the
unexposed parts soft. They are then washed away using a water spray, leaving
behind a clean area in the mesh with the identical shape as the desired image,
which will allow the passage of ink. It is a positive process.
In fabric
printing, the surface supporting the fabric to be printed (commonly referred to
as a pallet) is coated with a wide 'pallet tape'. This serves to protect the
'pallet' from any unwanted ink leaking through the screen and potentially
staining the 'pallet' or transferring unwanted ink onto the next substrate.
Next, the screen
and frame are lined with tape to prevent ink from reaching the edge of the
screen and the frame. The type of tape used for this purpose often depends
upon the ink that is to be printed onto the substrate. More aggressive tapes
are generally used for UV and water-based inks due to the inks' lower
viscosities and a greater tendency to creep underneath the tape.
The last process
in the 'pre-press' is blocking out any unwanted 'pin-holes' in the emulsion. If
these holes are left in the emulsion, the ink will continue through and leave
unwanted marks. To block out these holes, materials such as tapes, specialty
emulsions, and 'block-out pens' may be used effectively.
The screen is
placed atop a substrate. Ink is placed on top of the screen, and a flood bar is
used to push the ink through the holes in the mesh. The operator begins with
the fill bar at the rear of the screen and behind a reservoir of ink. The
operator lifts the screen to prevent contact with the substrate and then using
a slight amount of downward force pulls the fill bar to the front of the
screen. This effectively fills the mesh openings with ink and moves the ink
reservoir to the front of the screen. The operator then uses a squeegee (rubber
blade) to move the mesh down to the substrate and pushes the squeegee to the
rear of the screen. The ink that is in the mesh opening is pumped or squeezed
by capillary action to the substrate in a controlled and prescribed amount,
i.e. the wet ink deposit is proportional to the thickness of the mesh and or
stencil. As the squeegee moves toward the rear of the screen the tension of the
mesh pulls the mesh up away from the substrate (called snap-off) leaving the
ink upon the substrate surface.
There are three
common types of screen printing presses: flatbed, cylinder, and rotary. A
development of screen printing with flat screens from 1963 was to wrap the
screen around to form a tube, with the ink supply and squeegee inside the tube.
The resulting roller rotates at the same speed as the web in a roll-to-roll
machine. The benefits are high output rates and long rolls of product. This is
the only way to make high-build fully patterned printing/coating as a
continuous process and has been widely used for manufacturing textured
wallpapers.
Textile items
printed with multi-colored designs often use a wet-on-wet technique, or
colors dried while on the press, while graphic items are allowed to dry
between colors that are then printed with another screen and often in a
different color after the product is re-aligned on the press.
Most screens are
ready for re-coating at this stage, but sometimes screens will have to undergo
a further step in the reclaiming process called dehazing. This additional step
removes haze or "ghost images" left behind on the screen once the
emulsion has been removed. Ghost images tend to faintly outline the open areas
of previous stencils, hence the name. They are the result of ink residue
trapped in the mesh, often in the knuckles of the mesh (the points where
threads cross).
STENCILS
A macro photo of a screen print with a photographically produced stencil. The ink will be printed where the stencil does not cover the substrate
A method of
stenciling that has increased in popularity over the past years is the photo
emulsion technique:
1. The
original image is created on a transparent overlay, and the image may be drawn
or painted directly on the overlay, photocopied, or printed with a
computer printer, but made so that the areas to be inked are not transparent.
Any material that blocks ultraviolet light can be used as the film, even card
stock. A black-and-white positive may also be used (projected onto the screen).
However, unlike traditional plate-making, these screens are normally exposed by
using film positives.
2. A
screen must then be selected. There are several different mesh counts that can
be used depending on the detail of the design being printed. Once a screen is
selected, the screen must be coated with a photosensitive emulsion and
dried. Once dry, it is then possible to burn/expose the print.
3. The
overlay is placed over the screen and then exposed to a light source
containing ultraviolet light in the 350–420 nanometer spectrum.
4. The
screen is washed off thoroughly. The areas of emulsion that were not exposed to
light dissolve and wash away, leaving a negative stencil of the image on the
mesh.
NON-GARMENT USES
Screen with exposed image ready to be printed
See
also: printed electronics, roll-to-roll, and textile printing
Screen printing
is more versatile than traditional printing techniques. The surface does not
have to be printed under pressure, unlike etching or lithography,
and it does not have to be planar. Different inks can be used to work with a
variety of materials, such as textiles, ceramics, wood, paper, glass,
metal, and plastic. As a result, screen printing is used in many different
industries, including:
- Balloons
- Clothing
- Decals
- Medical devices
- Printed electronics, including circuit board printing
- Product labels
- Signs and displays
- Snowboard graphics
- Textile fabric
- Thick film technology
- Pinball machines
In screen
printing on wafer-based solar photovoltaic (PV) cells, the mesh and buses of
silver are printed on the front; furthermore, the buses of silver are printed
on the back. Subsequently, the aluminum paste is dispensed over the whole surface
of the back for passivation and surface reflection. One of the
parameters that can vary and can be controlled in screen printing is the
thickness of the print. This makes it useful for some of the techniques of
printing solar cells, electronics, etc.
Solar wafers are
becoming thinner and larger, so careful printing is required to maintain a
lower breakage rate, though high throughput at the printing stage improves the
throughput of the whole cell production line.
AUTOMATION
To print multiple
copies of the screen design on garments in an efficient manner, amateur and
professional printers usually use a screen printing press, which is a
colloquial term as most screen printing machines are vastly different from
Offset Printing Presses. Many companies offer simple to sophisticated
printing presses. These presses come in one of three types, Manual (also
referred to as Handbench), Semi-Automatic, and Fully Automatic. Most printing
companies will use one or more semi-automatic or fully automatic machines with
manual machines for small runs and sampling.
Whilst Manual
Screen Printing can be done with Carousels, Handbenches (both of which are
often referred to colloquially as presses), or even onto tables. Semi and
Fully-Automatic machines are broken into two main categories; Flatbed Printers (Poster,
Art Printing, or other flat substrates) and Carousels and Oval Machines
(Garments and other apparel, amongst other textiles). Both are
fundamentally similar in terms of automation but differ in areas such as
physical footprint and upgrade paths.
These machines
are much faster and use either pneumatic pressure generated by air compressors
or use electric motors to draw the squeegees, rotate, and raise or lower pallets
removing much of the manual labor from the task - resulting in significant
reductions in operator fatigue as well as more consistent results.
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