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Screen_Press_Printing_Looking_at_the_process
| Screen Press Printing: Looking at the process
Screen printing also called silk screen print also called
serigraph was invented in the Far East around 2000 years ago. No
supplemented data on when or where exactly it originates, but
originally used to make the screen printer's screen. A paper
stencil was stiched onto the screen to control the print area.
Around a hundred years ago screen printing was reinvented in the
west and it has become a common method of printing on textiles.
Most common, the custom t-shirts. The screens used for screen
printing custom t shirts, are made with a mono filament mesh.
Photopolymer emulsion is used to make the stencil. Thus, silk
screen is coated with the liquid emulsion, and allowed to dry
and harden. The emulsion is light sensitive. The stencil is made
in the "silk screen" by placing a positive of the print over the
coated silk screen then exposing the screen to light. The areas
of the screen shielded from the light remain water soluble and
can be washed out of the screen. The light affects the emulsion
in that once the dried emulsion has been exposed to light, water
will not dissolve it. Take a look at the photograph to the left.
In this case the positive for the screen print is hand drawn.
The availability of the screen printing products can be
purchased locally from screen printing process supply stores. An
"emulsion cup" is used to coat the silk screens with emulsion.
The emulsion cup is a trough like cup that holds the liquid
emulsion and allows it to be spread evenly across the screen.
The screen is held vertically and the emulsion is spread from
bottom to top with one smooth motion. After the silkscreen has
been coated with emulsion it will be left to dry. Ambient or
soft light can expose the screen but it would take hours or
days. Even so care should be taken that the silk screen is kept
in a dark place.
To "burn" a screen, the positive must make tight contact with
the screen. A four inch thick foam rubber pad is placed under
the screen with the glass placed on top. Sunlight can now expose
the silk screen. It can take anywhere from around two to fifteen
minutes. After the screen has been exposed it is taken to a wash
out area usually a metal bathtub like trough or large sink. The
screen is set in the trough and sprayed with a garden hose.
Rinsed with water, after a second the design will be visibly
lighter in the emulsion. After a minute or so of rinsing the
design area should be free of emulsion. Rinsing is continued for
another minute or so to wash away emulsion scum that if allowed
staying in the screen and dry will clog printing areas. The
washed out screen is then allowed to dry.
After it has dried the screen must be taped off. This is usually
done with masking tape. The areas around the edges not coated
with emulsion are taped front and back. The screen printer
applies tape liberally over the frame and screen areas. The
screen is then "pin holed". Sometimes imperfections in the
screen printing process cause tiny "pin holes" in the emulsion
that’s why these must be taped over or blocked with emulsion or
block out fluid. This is done on the bottom of the screen.
The emulsion can be removed from the screens so that the screens
can be reused. This is called "reclaiming" the screen. After the
print run the ink is scraped out of the screen and mineral
spirits or ink wash is used to clean the ink from the screen.
All the masking tape is pulled off the screen and the screen is
sprayed with “emulsion remover.” This chemical is left on the
screen for 2 or 3 minutes and a high pressure sprayer or even a
garden hose can be used to wash away the emulsion. After the
emulsion has been removed the screen must be degreased. There
are degreasing liquids available also ivory soap works well. The
screen is scrubbed thoroughly on both sides and then rinsed. It
can now be dried and if kept clean reused. The screens must
always be clean and degreased and dry before they can be coated
with emulsion.
These procedures may sound very difficult but the application is
totally easy. See and try the screen printing yourself!
For additional information and comments about the article you
may log on to http://www.aprintingpress.com
About the author:
Actually I’m not fond of writing, I don’t even write at all. I
am not expecting to be in this field. But nevertheless, I love
to read books...almost everything interest me. Reading is my
passion! And now that I am in an article writer team, writing
gives me an additional thrill in myself...Before I love to read
books but now I’m also in a writing stuff. I can say that I am
not a good writer but I am always trying to be one.
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