The Squeegee Story

Answers to frequently-asked questions

Is there one item that symbolizes our industry? One totem that is recognized by both apprentice and master? Of course, it's the squeegee. Yet I have a question: How come this low-tech, inexpensive tool of the trade is so often mistreated and last in line for problem-solving in our industry? After all, by filling the mesh with ink and keeping the mesh in contact with the substrate, the squeegee plays a leading role in screen printing.

The answer to this question, I suspect, lies in our lack of knowledge about the characteristics and use of the squeegee. Hopefully, by the end of this article, you will have enough Information to choose the right squeegees for your work and enough expertise to troubleshoot squeegee-related production problems.

What's a Squeegee Made Of?

It's been almost a decade since black neoprene and brown buna-N squeegees were supplanted by color-coded, high-density polyurethane squeegees. High-density blades resist the corrosive effects of inks and solvents, while the color coding (indicating the blade hardness) is especially useful in shops that print with a variety of inks and substrates. For example, a blue bullnose for dark-garment printing is easy to distinguish from an orange square edge used for halftone printing.

Some squeegees are composed of more than one material. To prevent roll-over from excessive squeegee pressure, printers used to shim soft blades with strips of aluminum. Today, some squeegees are available with a stiff material (a fiberglass sheet or hard polyurethane) between two layers of softer polyurethane. This provides the more flexible printing edge of a softer blade, while reducing the blade deflection. Some composite squeegees also come with a rigid material in the top two-thirds of the blade, while the softer polyurethane is on the bottom to serve as the printing blade.

What is Squeegee Durometer?

The durometer of a squeegee is the measure of its hardness, and a guide to the blade's ability to resist bending during printing. Squeegee durometers are measured on the Shore A scale, an industrial standard of 1-100 used to indicate the hardness of rubbery materials. The higher the durometer, the greater the blade rigidity. The lower the durometer, the more the blade will flex during printing.

You need to know that the instrument used to measure durometers is itself called a durometer. This device has an indenter pin, which is pushed onto the surface of the squeegee. The resistance in A Shore units is read from an analog dial.

Choosing a squeegee durometer, available from 50-95 Shore A, depends on your substrate, mesh count, and screen tension.

Very soft squeegees (for example, a 55 durometer) are soft enough to conform to varying garment thicknesses or uneven platen surfaces. However, they tend to bend under high squeegee pressure.

Harder squeegees (for example, an 80 durometer) are much less forgiving and will not print an even layer of ink on an uneven surface, such as a textured weave. However, these higher durometers are required to stand up to the high pressure needed to print at high speed or with high-opacity, high-viscosity thick plastisol inks.

Squeegee manufacturers, in pursuit of a you-can-have-it-all squeegee, have captured part of the market with alternatives to the single-durometer squeegee.

A multidurometer squeegee offers two durometers on the same blade and is available in two styles. The first is the front-back dual-durometer squeegee (for example, a 60/90 combination). One disadvantage of this style is that it offers only one printing edge and must be rested after sustained use. Pulled in only one direction, it tends to bow out. The harder back of the blade is also less permeable to solvents and tends to swell less than the lower-durometer printing layer.

The triple-durometer blade (for example, a 70/90/70 combination) was a natural step in the evolution of the squeegee. In our example, by laminating softer polyurethane on both sides of the 90-durometer material, the printer has two working edges and can avoid the bowing and warping problems of the dual-durometer squeegee.

Another answer to the must-be-stiff-to-avoid-roll-over-but-soft-to-follow-the-substrate question is to modify the blade holder. For example, the Indexable Squeegee®, from Printer's Edge, Warren, OH, has a squeegee holder that reduces the unsupported blade height, and thus maintains the rigidity of the squeegee (which can be a soft 60, or even 50, durometer). The blade is then advanced from the holder as needed, somewhat similar to the action of a mechanical pencil.

Yet another answer is to back a soft squeegee blade with a metal support. For example, the Flex-Control adjustable blade brace mounts a dialable plate behind the squeegee. Also manufactured by Printer's Edge, the device allows consistent control of the support of the squeegee.

One caveat: Durometers change depending on time and usage. At the end of an 8-hr press run, the ink chemicals will have permeated and softened the polyurethane. At 9:00 am it's a 70-durometer squeegee and by 6:00 pm it's softened to 65--and you wonder why the ink is laying down thicker and thicker? No problem. Just change the squeegee during your noontime break. However, over the longer term, your squeegees will harden. Through the months, the constant absorption and release of ink chemicals will interfere with the elasticity of the squeegee.

Which Squeegee Profile Works Best?

Not only are there a whole range of durometers, but also a chocolate-box of profiles (the shapes of the actual printing edges). Textile printers tend to stick with the straight and bullnose blades, selecting profiles depending on the mesh count and the desired thickness of the ink deposit . (Fancier beveled configurations are usually used on smooth glass and ceramic substrates.)

Straight-edge squeegees are the most popular among textile screen printers. A true 90

Is there one item that symbolizes our industry? One totem that is recognized by both apprentice and master? Of course, it's the squeegee. Yet I have a question: How come this low-tech, inexpensive tool of the trade is so often mistreated and last in line for problem-solving in our industry? After all, by filling the mesh with ink and keeping the mesh in contact with the substrate, the squeegee plays a leading role in screen printing.

The answer to this question, I suspect, lies in our lack of knowledge about the characteristics and use of the squeegee. Hopefully, by the end of this article, you will have enough Information to choose the right squeegees for your work and enough expertise to troubleshoot squeegee-related production problems.

What's a Squeegee Made Of?

It's been almost a decade since black neoprene and brown buna-N squeegees were supplanted by color-coded, high-density polyurethane squeegees. High-density blades resist the corrosive effects of inks and solvents, while the color coding (indicating the blade hardness) is especially useful in shops that print with a variety of inks and substrates. For example, a blue bullnose for dark-garment printing is easy to distinguish from an orange square edge used for halftone printing.

Some squeegees are composed of more than one material. To prevent roll-over from excessive squeegee pressure, printers used to shim soft blades with strips of aluminum. Today, some squeegees are available with a stiff material (a fiberglass sheet or hard polyurethane) between two layers of softer polyurethane. This provides the more flexible printing edge of a softer blade, while reducing the blade deflection. Some composite squeegees also come with a rigid material in the top two-thirds of the blade, while the softer polyurethane is on the bottom to serve as the printing blade.

What is Squeegee Durometer?

The durometer of a squeegee is the measure of its hardness, and a guide to the blade's ability to resist bending during printing. Squeegee durometers are measured on the Shore A scale, an industrial standard of 1-100 used to indicate the hardness of rubbery materials. The higher the durometer, the greater the blade rigidity. The lower the durometer, the more the blade will flex during printing.

You need to know that the instrument used to measure durometers is itself called a durometer. This device has an indenter pin, which is pushed onto the surface of the squeegee. The resistance in A Shore units is read from an analog dial.

Choosing a squeegee durometer, available from 50-95 Shore A, depends on your substrate, mesh count, and screen tension.

Very soft squeegees (for example, a 55 durometer) are soft enough to conform to varying garment thicknesses or uneven platen surfaces. However, they tend to bend under high squeegee pressure.

Harder squeegees (for example, an 80 durometer) are much less forgiving and will not print an even layer of ink on an uneven surface, such as a textured weave. However, these higher durometers are required to stand up to the high pressure needed to print at high speed or with high-opacity, high-viscosity thick plastisol inks.

Squeegee manufacturers, in pursuit of a you-can-have-it-all squeegee, have captured part of the market with alternatives to the single-durometer squeegee.

A multidurometer squeegee offers two durometers on the same blade and is available in two styles. The first is the front-back dual-durometer squeegee (for example, a 60/90 combination). One disadvantage of this style is that it offers only one printing edge and must be rested after sustained use. Pulled in only one direction, it tends to bow out. The harder back of the blade is also less permeable to solvents and tends to swell less than the lower-durometer printing layer.

The triple-durometer blade (for example, a 70/90/70 combination) was a natural step in the evolution of the squeegee. In our example, by laminating softer polyurethane on both sides of the 90-durometer material, the printer has two working edges and can avoid the bowing and warping problems of the dual-durometer squeegee.

Another answer to the must-be-stiff-to-avoid-roll-over-but-soft-to-follow-the-substrate question is to modify the blade holder. For example, the Indexable Squeegee®, from Printer's Edge, Warren, OH, has a squeegee holder that reduces the unsupported blade height, and thus maintains the rigidity of the squeegee (which can be a soft 60, or even 50, durometer). The blade is then advanced from the holder as needed, somewhat similar to the action of a mechanical pencil.

Yet another answer is to back a soft squeegee blade with a metal support. For example, the Flex-Control adjustable blade brace mounts a dialable plate behind the squeegee. Also manufactured by Printer's Edge, the device allows consistent control of the support of the squeegee.

One caveat: Durometers change depending on time and usage. At the end of an 8-hr press run, the ink chemicals will have permeated and softened the polyurethane. At 9:00 am it's a 70-durometer squeegee and by 6:00 pm it's softened to 65--and you wonder why the ink is laying down thicker and thicker? No problem. Just change the squeegee during your noontime break. However, over the longer term, your squeegees will harden. Through the months, the constant absorption and release of ink chemicals will interfere with the elasticity of the squeegee.

Which Squeegee Profile Works Best?

Not only are there a whole range of durometers, but also a chocolate-box of profiles (the shapes of the actual printing edges). Textile printers tend to stick with the straight and bullnose blades, selecting profiles depending on the mesh count and the desired thickness of the ink deposit . (Fancier beveled configurations are usually used on smooth glass and ceramic substrates.)

Straight-edge squeegees are the most popular among textile screen printers. A true 90° angle, straight-edged squeegee is used with mesh counts of 230 threads/in. or higher. However, sometimes the knuckles of the mesh will cause excessive vibrations with a sharp edge as it rises and drops into each valley of the mesh. This undesirable washboarding can be eliminated by skewing the angle of the squeegee path slightly, so that the right side of the squeegee leads its left side slightly.

Another solution to the bouncing is to blunt the sharp edge of the squeegee. You can gently dull the edge with very fine sandpaper, using straight, even strokes across the entire length of the blade.

Your dull-edged squeegees-whether by sanding or natural mesh abrasion--are compatible with mesh counts of 100-200 threads/in.

For puff or glitter ink, or a white printer, mesh counts coarser than 96 threads/in. dictate the use of a bullnose profile. Such a rounded profile mashes the ink into the mesh and provides a thicker deposit on the substrate. Of course, low mesh counts, thick ink deposits, and rounded squeegees preclude fine-detailed designs.

What Kind of Squeegee Edge Do I Need?

For those fine details found in high-quality production runs, especially on automatic presses, not only must your squeegee edge be sharp, but also free of nicks, waves, and varying blade height. A tiny smidgen nicked out of a straight edge can translate into nasty streaks, especially noticeable in large areas of a single-color design printed with transparent inks.

Waves in the printing edge might be due to compression of the holder screws, swelling from chemical action, or incorrect squeegee storage. These waves will blight your printing with poor coverage (or even a color shift) due to uneven ink deposit where the squeegee is unable to "kiss" the mesh and clear the screen.

If the blade height is not uniform across the screen, you might find one side or corner of your print is out of registration. Maladjusting the platen level to compensate for the poor printing might even ruin a well-designed automatic press.

Instead of pitching the blade, why not resharpen it? Squeegee sharpeners (ranging from $400 wheel-type sharpening kits to 16-ft-long automatic belt-type mega-machines that will do everything, including help you apply for a second mortgage) can remove a thin layer from an 80- or 90-durometer squeegee blade and restore a perfect edge. Many printers use an abrader wheel for softer durometer squeegees. An automated machine with a special blade-holding device is also available.

One distortion that sharpeners cannot correct is lateral warping or meandering of the blade from left to right. Such twisting is probably due to improper care of the tool.

How Long Should the Squeegee Be?

Squeegee length should fit the image being printed. Choose a blade that extends about 1 in. beyond each side of the widest section of the design.

The squeegee also needs to fit within the screen. If the end of the blade is too close to the frame, the ends of the squeegee will exert excess pressure on the stencil and cause pinholes. There should be at least 2 in. of free space between the image and the screen frame. For example, if the width inside your frame is 22 in., your squeegee should not be longer than 18 in.

Most squeegee manufacturers recommend rounding the sharp ends of every squeegee blade. A rounded end is less likely to dig into and fatigue the stencil, resulting in a band of pinholes.

What is a Good Angle of Attack?  

If you hold your squeegee at 90° to the mesh, you will be unable to muster enough pressure to compress the ink into the screen. Conversely, if you reduce the blade angle so the blade is too close to the screen, you will push too much ink through the mesh.

Most printers find that pulling the squeegee at 15-20° off the vertical ensures an even deposit of ink. The setting of the exact angle depends in part on the squeegee's profile and durometer.

If you are printing puff, glitter, or a thick undercoat with a bullnose-profile squeegee, the angle will make little difference, since a round edge is, well, round on all sides.

How Important Is Squeegee Speed?

The speed of the squeegee affects the rate of ink flow into the mesh openings. With plastisol inks, the faster the blade is racing, the less the ink will penetrate the mesh. In such cases, the printed image will be poorly covered. You could say haste makes for a full reject box. But yet again, we must qualify our statements.

You will not be able to speed your squeegee if your ink is too thick. You can either reduce the ink (use a curable or finished reducer or soft-hand extender) or step up to a harder durometer squeegee to gain more shearing power.

Talking about shear, remember that plastisols change when they are stirred. As the ink is worked back and forth over the mesh, it thins slightly, due to the heat and agitation generated by the squeegee action. You may need to adjust the squeegee speed by the end of a long printing run.

On the other hand, water-based inks (including discharge inks), which are less viscous than plastisols, can be printed at higher speeds. In general, inks tend to print better with higher squeegee speeds.

How Much Pressure Can Your Print Take?

My first magic pull of a squeegee was a disaster. In my enthusiasm, I bent my back to the chore and gave it my all. Too much pressure resulted in misregistration. Where the design required knife-edge sharpness, I had printed a furry mess. The thick layer I had mashed through the screen never did cure properly, and I was wasting ink. I also learned that if I kept it up, the pressure would ruin the screens and even wear down the squeegees. I discovered that the best production runs are the result of a light touch--assuming all other factors are optimal.

Once correctly set, these factors--adequate screen tension, proper durometer for the mesh count, suitable ink viscosity, and minimal off contact--will allow you to make minor squeegee-pressure adjustments, resulting in the perfect print.

Think about it: The easiest component to change in a manual press run is the squeegee pressure. If part of the print is not covering well, use more muscle. If there are streaks, use more muscle. You sorta get an image of The Hulk, grunting as he flattens the squeegee and makes that *!ª#*?! ink do what it should.

This picture is all wrong. What you want is the least amount of pressure--think bantam weight, not World Wrestling Federation.

Can I Avoid Printing Pain?

Another reason to avoid heavy squeegee pressure is a disastrous spinoff of the age of specialization: carpal tunnel syndrome. This syndrome (characterized by tingling, numbness, fatigue, and/or pain in your arms and hands) can be prevented by rotating staff assignments in the shop, altering the squeegee grip and/or stroke direction, or padding the holder. SqueegeePlus! of Eugene, OR, manufactures an inexpensive, ergonomic neoprene pad that can be retrofitted to most squeegee holders. This pad changes the traditional pinch grip into an open-palm grip, thus reducing the chances of developing this debilitation.

What Care Do Squeegees Need?

In closing, a few basic tips on the care of your squeegees are worth listing:<P>If your squeegees arrive coiled, store them flat and away from heat. Blades should always be hung or laid straight.

Allow squeegees to rest between runs and before resharpening. Preferably, rotate them after 4-5 hr on the press. As Don Pierce of Washington, PA-based Pleiger Plastics recommends, "Develop a rotation program with at least three squeegees per station. It will keep your squeegees living 30-40% longer."

At the end of every press run, wipe and clean your squeegees with a mild solvent. Never soak a blade in ink or cleaning solvent.wisely choosing and caring for your squeegees, there should be fewer times you are faced with the oldest question in screen printing: Why won't it print right?!

Some manufacturers of squeegees and squeegee-related products

ACLA USA, PA 412-776-0099

A.W.T. World Trade, Inc., IL 312-777-7100

Apolan International, NJ 908-922-6570

Crown Art Products Co., Inc., NJ 201-777-6010

Fimor/Euroscreen, OH 800-531-5566

Encore Engineering, FL 800-922-5138

Majestech Corp., NY 800-431-2200

Miller Process Coating Co., PA 800-742-9170

One Stroke Inks &amp; Supplies, KY 800-942-4447

Pleiger Plastics, PA 800-753-4437

Printer's Edge, Ltd., OH 800-467-3343

SqueegeePlus!, OR 503-484-6449

Svecia USA, Inc., NJ 201-337-7786

Unipur USA, NJ 201-680-9858

Unitex Ltd., England 44-423-862-677

Zim International, GA 800-241-8181
 

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