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Despite the vital part the squeegee plays in the screenprinting process, nothing could be simpler than the squeegee itself. It's merely a thin blade of flexible, rubbery material fitted into a rigid support. But this simple tool has several jobs to do during the printing process. First, it has to force the mesh down into contact with the surface of the substrate. This means it must be firm enough to overcome the tension in the mesh, at least for the off-contact distance between screen and substrate. Second, it has to fill the open channels of the stencil with ink, and then carry the excess ink away from the surface of the substrate at the conclusion of the print stroke. To accomplish this, the blade has to be sufficiently firm to transfer the force of the printer's effort to the screen, yet flexible enough to bend slightly under the pressure to generate downward force on the ink.

The Parts of a squeegee
A squeegee has only two parts: the blade and the holder. In manual printing the holder is usually called the handle. The top supplies a grip for the hands of the printer, the bottom a solid channel to support the upper part of the blade. The exposed, or free area of the blade, amounts to only about 75% of its total width. The actual amount varies depending on the type of handle used. The blade does most of the work of moving ink across the screen, but without the firm backing provided by the handle it would be quite useless for printing. The handle not only holds the blade straight, it keeps the upper part of the blade rigid while allowing the lower part to flex with the print stroke.

Squeegee handles for manual printing
Those who have never logged long hours with their hands wrapped around a squeegee handle might be forgiven if they undervalue the part it plays in the printing process. Few experienced printers would make that mistake. After all, the handle allows the printer to exert direct physical control over the printing process. Many printers develop strong preferences and tend to stick with a favorite type.

When it comes to selecting a handle for your squeegee there are three variables to consider: materials, shape, and size. Handles can be made of wood, plastic, or aluminum. The first squeegee handles were made of wood and wooden handles remain popular among printers to this day. Many still prefer the feel of wood to that of aluminum or plastic. Others are equally devoted to the newer materials and praise them for being easy to clean. Ink can't penetrate into aluminum or plastic as it can with wood, and clean up is as simple as a quick wipe or two with a cloth or paper towel.

One clear advantage of at least some of the aluminum handles is that changing blades can be a snap. All you do is unscrew a couple of clamps. In a wooden handle the blade is usually held in place by a series of Chicago screws. A Chicago screw, which also goes under a variety of other names, is a special two-part combination consisting of a screw that fits into a threaded post. To assemble a wooden-handled squeegee you have to drill through both sides of the u-shaped channel plus the upper part of the blade and insert one of these screws every few inches. Changing blades means having to remove and reinstall quite a few screws.

A good handle will fit the hands of the printer, in size as well as shape. The most common widths are 4 " and 5". If you have small hands, the 4" width would probably be a better fit. In recent years, a host of new ergonomic squeegee handles have appeared on the market to combat the carpal tunnel syndrome and other stress-related injuries common among screenprinters. You can find quite a few different shapes out there, and you would be well advised to try as many as you can. If you prefer to stick to your old standard shape and you find yourself experiencing pain in your lower arms, try padding it with a layer of compressible material like neoprene.

The one-arm squeegee
Screenprinting can be categorized as either manual or automatic, depending on whether the squeegee has a human or mechanical operator. The term manual printing makes one think of a printer pulling his squeegee with the traditional two-hand grip. But it can also mean printing done with a one-arm or one-man squeegee, so named because the printer needs only one hand to operate it. A counterweight supplies pressure to the opposite end of the squeegee. During a print stroke the counterweighted end slides along a metal track so that it keeps perfect pace with the end pulled by the printer. Using a one-arm squeegee, a printer can pull quite large prints with relatively little effort.

The one-arm squeegee usually comes with a print table, often equipped with a vacuum pump to secure substrate during the printing process. A one-arm press can be purchased for a fairly modest investment (a quick on-line search turned up several used one-arms for under $3000). A new one might cost nearly twice that amount, depending on size. But it's an investment worth considering because a one-arm is really an ideal piece of equipment for a small sign shop.

One-arms and a number of automatic presses still use some sort of blade holder to support the squeegee, but there's no choice involved. You simply have to buy the kind of holder designed to fit your press.

Squeegee blades
The squeegee blade is part of the squeegee that actually does the printing. Blades were once made of rubber or neoprene (synthetic rubber), but today most blades are made of polyurethane, a flexible, highly dense plastic. Polyurethane is easily formed yet resistant to most solvents, and it can be colored, which allows manufacturers to color-code their blades according to their durometer, or hardness. Durometer, a term used to describe the hardness of a rubbery-type material, is measured according to a standard known as the Shore A scale. Occasionally you may hear someone use the word Shore to describe the hardness of the blade rather than durometer. Both really mean the same thing.

There are many different types of squeegee blades on the market. They differ from one another in three important qualities:

1. Durometer
2. Shape or profile
3. Width

Virtually all squeegee blades used in screenprinting today fall somewhere between 50 and 90 durometers. The durometer of a blade can make a big difference in the prints it produces. Softer blades (50-60 durometers) will tend to lay down much more ink than harder blades. They also do a better job of printing on rough surfaces like fabrics. The mesh in your screen is another factor that can determine your choice of a squeegee blade. As a rule, the coarser the mesh the lower the durometer of the blade you'll want to use.

For printing most sign materials, which tend to be comparatively smooth-surfaced and not very absorbent, you would do well to select a squeegee blade in the middle range, somewhere around 70 to 80 durometers. The harder the squeegee the lower the ink deposit. The very hardest blades (90 or more durometers) are used for printing fine detail work and halftones. They are also used for UV printing where a light ink deposit is preferred.

Double- and triple-durometer squeegee blades
In recent years, squeegee blade manufacturers have come up with a way of blending materials of different durometers together in a single blade. The most basic approach is to place them back to back with a softer durometer printing edge backed up by polyurethane of a harder durometer. For example, the print side may be 60 durometers and the supporting side 90 durometers, a combination that's usually written 60/90. Blades of more than one durometer are often called composite blades.

The harder-durometer backing provides support for the lower-durometer side of the blade. This creates a firm squeegee with a printing edge that retains the flexibility to ride over rough-surfaced substrates and still lay down a good thick ink deposit.

The problem with such a dual-durometer combination is that only one side, the 60-durometer side, can be used for printing. Some squeegees have been designed with the harder layer stacked on top of the softer layer. This gives you the same kind of support for the softer printing edge as the back-to-back type, but you can now print with both sides of the blade.

Triple-durometer blades sandwich a higher durometer layer in the middle of two lower- durometer slices. Some typical triple durometer blades would be 60/90/60 or 70/90/70. Still another type of composite sandwiches a core of a different material, like fiberglass, within the polyurethane outer layers. This firm supporting layer begins well back from the printing edge, so there is never any danger of it coming into contact with the screen.

Other types of blade support are external. In some presses a metal backing plate attached to the squeegee holder supports the upper part of the squeegee blade. The metal plate runs along the entire length of the squeegee blade.

Despite the many different combinations available, a beginning screenprinter would do well to start out with a standard single-durometer blade. The best choice of durometer would probably fall somewhere in the middle of the range. After a new printer has pulled a few hundred prints, it's time to try out squeegee blades of different durometers, perhaps even a few of the double- and triple-durometer composites. Squeegee preferences are largely a matter of feel, and it takes time and experience to discover what feels good to you.

Shape (profile)
Squeegee blades are also offered in a variety of shapes:

1. Square-edge
2. Round-edge (also called "ball-nose")
3. Single-bevel
4. Double-bevel

There are others, but these are the basic profiles. Most of us are familiar with the square-edged profile. This is the profile used for printing most substrates, T-shirts and signs, for example. The round-edge blade is used when a printer wants to lay down an exceptionally thick layer of ink. Its most frequent application is in the printing of certain kinds of fabric. The single-beveled profile is widely used for printing on glass; the double-bevel is the shape of choice for use in automatic cylinder presses. The square-edge profile is the one you want for sign printing. But be aware that these other profiles exist, and remember to specify the profile when ordering blades from your supplier.

Blade dimensions
The standard square-edged squeegee blade is 3/8" thick and 2" wide. There are different sizes on the market, but this is the normal size used in sign printing. The next dimension to consider is length. The simple answer is that it should be long enough to overlap the artwork by a comfortable margin, usually an inch or more, depending on the size of the artwork you're printing. If your squeegee is too short, there's a chance it will drift off to one side or the other during the print stroke and leave part of the image unprinted.

A squeegee that's too long, on the other hand, will come too close to the inside of the frame. The mesh loses much of its elasticity close to the frame. If the ends of the squeegee stray into this area, the mesh can't flex properly during the print stroke, which causes a host of printing problems. Not only does the printer have to work harder to pull his print, but a lot of extra wear and tear takes place on both the screen and the squeegee. Keep several inches clearance between the frame and the squeegee.

So, now that we know what to look for when ordering a squeegee we need to know how to print with it. Next time we'll put that squeegee to work and take a look at the subtle art of pulling a print.