Most in our industry will pinpoint the screen as the most important tool in the printing process, but the squeegee will come along as a close second.
The squeegee, the durometer (hardness), the angle and the pressure will
have the next greatest impact on the appearance of your final printed
product.
In garment printing, the squeegee blade will most commonly be polyurethane. Blade material can be cut to your specified length,
either by your supplier or by yourself in your own shop. For manual
printing, the blade and squeegee holder are often cut to length in a
single process from a larger fully assembled squeegee.
Squeegee blade material is also readily available from suppliers for
you to cut and attach to the handle yourself. Finished squeegees and
separate blade materials are almost always purchased by the inch and to
your specification.
Squeegees have several functions:
1.) Pushing ink through the screen and onto your garment. The amount of ink forced through the screen is determined by the mesh size and the ink viscosity (thickness).
2.)
Causing the screen mesh to come into contact with the garment. This
contact will also be affected by screen tension and the off-contact
distance between the screen and the platen.
3.)
Sheering the excess ink from the print area on your screen. By sheering
away the ink from the print area, no ink is left in the screen that
might pull the ink on the garment back up into the screen. Lack of
proper sheering of the ink from the print area can cause an uneven lay
down of ink and a rough surface to your finished print.
Durometer
Durometer refers to the hardness of the squeegee. Durometer affects the amount of printing force you can apply to the screen and garment. Softer squeegees result in less force than harder ones. There are three most common categories of squeegee blade durometer.
- Soft (approximately 60 durometer and below) squeegees will be used when you want a heavier lay down of ink. A soft durometer squeegee can be used for inks such as puffs,
where a heavy deposit of ink is required to achieve the puff effect.
You might also select a soft squeegee for fabrics that require a heavier
deposit of ink such as fleece.
- Medium (approximately 70 durometer) squeegees are a middle of the road option, and will be used for general printing. This will be the tool of choice for most of your day to day production.
- Hard (approximately 80 durometer or higher) squeegees will lay down the least amount of ink and are most common for printing process and simulated process jobs
when fine lines and halftone dots are needed. You might also select a
hard squeegee based on the fabric substrate (such as nylon jacket
material), where the ink will set on top of the fabric, and therefore
require less ink for the job.
- Multi-durometer squeegee blades (70/90/70 for example)
are made of two or three layers of different durometer squeegee
material. A harder blade will generally be sandwiched in the center of
softer squeegee material to lessen the “give” of the blade. This layered blade is most common for process and simulated process work. The stiff center will help in the sheering of ink, while the softer outer edge will lay down slightly more ink. You’ll see these multi-durometer squeegees in many automatic shops, as well as manual shops for fine detail work.
Profile
Blade profile is the shape of the actual squeegee printing edge. A square profile is most common in garment printing,
and provides the maximum ability to sheer the ink from the print area
of the screen. Round squeegees provide a heavier lay down of ink. There
was a time in textile printing when rounded blades were used for
printing inks such as puffs, to maximize lay down of ink. Most printers
today will opt for a softer but square edged blade for heavy ink
deposits.
Pressure is the downward force you apply to the squeegee blade.
In automatic printing, this is a set adjustment. In manual printing, it
is a "feel" you will develop over time and with experience. There is a
balance that must be achieved. You must apply enough pressure to
sheer the ink from the screen, using only the sharp edge of the
squeegee blade. Too much pressure and the blade will "roll over", and
you will be printing with the flat side of the blade rather than the
edge. The result will be either too much ink lay down, or ink
being left in the print area of the screen instead of on the shirt. A
softer squeegee blade will tend to "roll over" more than a harder blade.
Squeegee Care
It is important to thoroughly clean your squeegees.
Most printers will clean the blade and handle with a solvent solution
right after printing. Take extra care in cleaning the area where the
blade meets the handle.
It's a good idea to reserve particular squeegees to be used with particular ink colors.
This will save you spoiled shirts and spoiled ink when red ink from
under the squeegee blade suddenly appears in the white ink in the
screen.
If you use a solvent tank
or tray, do not soak the blades for extended periods of time. This
soaking of the blade material can cause swelling or distortion of the
blade, ruining it for future use.
Store squeegees either on a hanging rack
or in a handle down/blade up position on a shelf. Never store squeegees
resting on the blade. The blade will eventually warp or distort and
become useless.
If you discover nicks in the squeegee blade, showing up in your print as a heavier deposit line, you have two choices.
You can sharpen the blade with either a professional sharpening device
or a homemade sharpener created from fine sandpaper attached to a board.
Or you can remove the blade from the handle and replace it with new
blade material. Replacing the blade is the most common option.
Today, there are ergonomically shaped squeegees,
blades created for pushing rather than pulling, and new approaches to
the process with each coming trade show. But for now, the most common approach will be the standard wood handled device, chosen simply by the proper durometer to match your chosen ink and substrate.