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Step 1 - Making The Screen
The first step in the screen printing process involves
making the screen. The screen consists
of a wooden or aluminum frame with a fine nylon mesh stretched over it. The mesh is pulled tight over the screen and is
either glued or screwed to the frame.
Each screen is made custom to each new design. If the design calls for a high resolution
print (i.e. half tones), a higher mesh count will be used. The mesh count is measured in TPI, which is the
number of threads per inch in the screen.
Most screen printers will vary between three basic meshes they use for
screens depending on what ink is being used and how much detail is in the art
work.
Step 2 - Coating The Screen
Next the screen is de-greased and
dried to make it print ready. After
drying, the screen is coated with a light sensitive emulsion and left to
dry. Now that the screen is ready, each
color in the custom art work must be separated.
A positive of each color is printed on film with registration marks so
that each color can be lined up properly while printing.
Step 3 - Making The Stencils
Each film is then overlaid onto its own
screen where it will be exposed to an ultraviolet light on an exposure
unit. After being exposed to the light,
the emulsion under the area where the image laid will be washed away with a
high pressure washer and the emulsion on the screen that was exposed to the light
will harden. This leaves you with an
open stencil to the exact size that was on the film. This process is repeated for each color in
the design and then the screens are taped off along the edges to prevent any
ink from possibly permeating through the screen where it should not.
Step 4 - Printing The Shirts
The screens are then fitted to a manual or
automatic printing press depending on the quantity of pieces ordered and the
substrate (i.e. T-shirt) is place below it. The ink color to be used is placed
on top of each corresponding screen and then the screen is lowered on top of
the substrate. A rubber blade, called a
squeegee, is then pulled across the screen pushing the ink through the mesh
where the stencil is and onto the surface of the substrate. The area of the screen where the emulsion has
hardened will prevent ink from penetrating the mesh. This process is repeated with each color in
the custom design until there is a finished image on the substrate.
Step 5 - Drying The Ink
After each ink color is added and the custom
design is completed the substrate must be placed in a dryer so that the ink can
reach 330°F to dry. In the case that the
substrate that is being printed on is a dark color, flashing is incorporated
into the process. Flashing entails
making a screen of the whole design that will be printed with white ink, called
an under base. The substrate then goes
to a flashing station where it is exposed to heat so that the ink dries before
the next color is printed. The substrate
is flashed between colors which results in a bright professional quality
print. Each screen is cleaned with an
emulsion remover after each custom design is finished printing so that they can
be re-used at a later date.
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