printing is a printing technique that uses a woven mesh to support
an ink blocking stencil. The attached stencil forms open areas
of mesh that transfer ink as a sharp-edged image onto a substrate.
A squeegee is moved across the screen stencil forcing or pumping
ink past the threads of the woven mesh in the open areas.
is made of a piece of porous, finely woven fabric called mesh
stretched over a frame of aluminum or wood. Originally human
hair then silk was woven into screen mesh, currently most mesh
is made of man made materials such as steel, nylon, and polyester.
Areas of the screen are blocked off with a non-permeable material
to form a stencil, which is a negative of the image to be printed;
that is, the open spaces are where the ink will appear.
is placed atop a substrate such as polystyrene, paper or fabric.
Ink is placed on top of the screen, and a floodbar (also known
as a fill bar) is used to fill the mesh openings with ink. The
operator begins with the floodbar 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 floodbar 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 equal to
the thickness of the mesh and or stencil. As the squeegee moves
toward the rear of the screen the tension of the mesh pull the
mesh up away from the substrate (called snap-off) leaving the
ink upon the substrate surface.
Screen Printing Process
three types of screenprinting presses. The 'flat-bed' (probably
the most widely used), 'cylinder', and 'rotary'.
items are printed in multi-color designs using a wet on wet
technique, while graphic items are allowed to dry between colors
that are then printed with another screen and often in a different
Reclaiming A Screen
can be re-used after cleaning. However if the design is no longer
needed, then the screen can be "reclaimed", that is
cleared of all emulsion and used again. The reclaiming process
involves removing the ink from the screen then spraying on stencil
remover to remove all emulsion. Stencil removers come in the
form of liquids, gels, or powders. The powdered types have to
be mixed with water before use, and so can be considered to
belong to the liquid category. After applying the stencil remover
the emulsion must be washed out using a pressure washer.
are ready for recoating 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 in 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, those points where threads overlap.
public thinks of garments in conjunction with screenprinting,
the technique is used on tens of thousands of items, decals,
clock and watch faces, and many more products. The technique
has even been adapted for more advanced uses, such as laying
down conductors and resistors in multi-layer circuits using
thin ceramic layers as the substrate.
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. Screenprinting
inks can be used to work with a variety of materials, such as
textiles, ceramics, wood, paper, glass, metal, and plastic.
As a result, screenprinting is used in many different industries,
from clothing to product labels to circuit board printing.