How properly tensioned screens save you money
Screens with proper tension can do more than simply eliminate puzzling printing problems; they can help make your entire screenprinting operation more efficient.

Some kind of mesh tension has to exist for the screenprinting process to work. There are two possible sources of that tension, either the screen or the squeegee. A printer working with an under-tensioned screen really has no choice except to increase the off-contact distance and push harder with his squeegee to supply that missing tension. When working with a properly tensioned screen, a printer doesn't have to push down as hard, and he can pull prints with less effort, so print jobs run faster and easier.

Tension, however, begins to have an effect on a print job long before the first print is pulled. When coating a properly tensioned screen with direct emulsion, screenprinters find it far easier to apply a smooth and even coat of emulsion. Coatings also tend to be thinner and more consistent across the screen. Because of this, screens will dry more quickly, a great time saver and an especially welcome one when you're trying to build up multiple layers of emulsion on a screen. Finally, when it comes time to expose those screens, that even coating of emulsion will expose more evenly and wash out with less effort.

Because a printer using properly tensioned screens doesn't have to use exaggerated pressure on the squeegee, the mesh takes less of a beating during every print stroke. Consequently, screens last longer. Because screens are subject to less wear during printing, they can deliver more prints per screen and a significant saving to your bottom line.

Some printers who have gotten used to working with under-tensioned screens often worry about higher-tensioned screens being more vulnerable to damage, but that simply is not true. Given reasonable care, they will last at least as long as an under-tensioned screen, and will wear considerably better. Reduced wear is a direct result of the much smaller off-contact distances, which means less wear and tear on the stencil, too. The stencil has to follow the movement of the mesh, but stencil material isn't nearly as flexible. In an under-tensioned screen, the stencil has to flex quite a bit more than it was meant to, causing it to break down earlier and develop tiny cracks. Yes, improper tension can even cause pinholes!

Improved print quality
Proper mesh tension also creates noticeable improvements in print quality, notably images with sharp, well-defined edges and smooth uniform color. This is how it works: As the squeegee passes over the mesh, tension quickly lifts it up off the substrate, getting it up out of the way of the ink. This also allows the ink to flow very slightly, eliminating mesh marks and leaving a smoother ink surface. Prints also tend to be more consistent because the reduced off-contact distance means a printer doesn't have to work as hard and he can exert more control during his print stroke. As a bonus, he may even find he uses slightly less ink to print a job.

How tension affects registration
With under-tensioned mesh, a printer will find his squeegee actually drags the fabric with it during the print stroke. In fact, it stretches the mesh slightly, because the mesh simply doesn't have the tension to resist the pull. This not only increases the likelihood of a blurred print, but the stencil also gets pulled right along with the mesh. The result is that the imprint moves a bit further down the substrate. When printing a two- or three-color job, this can become a real problem, especially if the job happens to be one that demands close registration. The images that should just meet, overlap and the imprints that should touch don't.

Furthermore, there will be inconsistencies from print to print depending on how much squeegee pressure was applied. Remember, the squeegee will actually pull the mesh down with it, so variations in squeegee pressure will show up in imprints that have shifted to varying degrees. But another registration problem results from the exaggerated off-contact distances required by under-tensioned mesh. When mesh has to travel a greater distance to reach the surface of the substrate, it becomes harder to control the position of the imprint.

Properly tensioned mesh not only insures greater print-to-print consistency but also makes it easier to match reprinted jobs to earlier runs. If you have to make a new stencil, and both old and new screens are close to recommended mesh tensions, there's a greater likelihood that the stencils will be identical. If you will be adding the screen to your library, the reduced screen wear will give you more prints before you eventually have to reshoot the screen.

With the importance of proper tension in mind, should a printer stretch his own screens? Virtually every newcomer to screen printing imagines he can save lots of money by making his own screens. This is probably one of the biggest time-wasters in the business. Without a professional tensioning system and the guidance of a tension meter there is no way to get screens close to specified tensions. For a beginner, an investment in professionally made screens is a very wise choice indeed, because it eliminates so many of the tension-related variables in the printing process. That leaves him free to concentrate on learning how to control all the other factors in screenprinting. Stretching screens in-house probably only makes sense in a very high-volume shop with an owner prepared to make a considerable investment in equipment and training. Mesh tension is one thing it doesn't pay to take lightly.