Screen Mesh Tension is Critical to Success
In screen printing, it’s really all about the screen. More specifically it’s using the right mesh count, and having that mesh stretched to the proper tension. Let’s assume you’re using the right mesh count. If you don’t know, the mesh count is probably too low. But in this article, let’s talk about proper tension, whether you use wood, static aluminum or retensionable frames.
Tension of your screen mesh is measured in “Newtons”, or more specifically, Newtons per centimeter. To measure tension, a weighted Tension Meter is rested on the fabric and the deflection (how much the fabric “gives”) is denoted by a number. For example, 25-35 Newtons will be a good tension range for garment printing.
A tension meter will cost in the neighborhood of $500.00, so it is not absolutely required when getting started. But, if you choose to use retensionable frames, a tension meter is necessary to achieve proper mesh tension during the stretching process. How it’s Done
To determine the tension of your screen, lay the screen on a flat surface with the print side (mesh side) up. Looking at the screen from the top (the narrow side where you stand when printing), place the meter in the center of the screen so that you can see the face of the meter. The needle will point to the number that will correspond to the tension of the mesh from side to side.
Now, move to the side of the screen (long side) and place the meter in the center so you can see the face. This will tell you the tension of the mesh from the top of the screen to the bottom.
The ideal tension will be in the 25-35 Newton range. There are special high tension mesh
products available, but for garment printing there is much debate about this product. My personal opinion...these higher tensions are a bit of overkill and unnecessary. Industry experts will argue the point but that’s my take on the subject. Most everyone will agree that high tension mesh is very difficult to use when printing off-contact on a manual press.
As a rule of thumb on my production floor:
25-35 – an excellent tension range, especially for process and simulated process work
15-20 – acceptable for most common jobs
10 Newtons and below – the screen should be discarded or restretched Low Tension
So what’s the big deal about having screens with proper tension? There are two issues that may arise when you have screens with too soft mesh. These are fabric wave and mesh release.
Fabric wave means, as you apply pressure and pull (or push) the squeegee across the screen
and shirt, a small wave of screen mesh may form in front of the squeegee blade. This wave of fabric can fill with ink as it passes over the image, and then smear ink onto the garment when the squeegee reaches the edge of the graphic. At best, your image will have a muddy edge throughout, rather than crisp lines.
The more common issue is mesh release. For best results, we print garments off-contact. This means the only place the screen physically comes into contact with the garment is along the sharp edge of the squeegee blade. If your screen mesh is too soft, the mesh will not release from the garment as you pull the squeegee across the image. When the mesh does release, often not until you lift the screen, the ink on the shirt will try to hold onto the screen mesh, causing a rough finish to your print.
On a multi-color job, soft mesh will stick to the previous colors on the shirt, and the ink picked up will begin to build up on the backs of your subsequent screens. In short order, your prints will start to appear muddy around the edges and where colors touch within your image.
When printing dark garments, poor screen tension can be doubly troublesome. The ink from the white underbase print is pulled up with the screen, and then flash cured into that position. My best analogy is seeing a thousand little snow covered mountain peaks standing up on the shirt. Under a microscope, the surface would look like the Alps. When colors are printed on top, the print feels very rough, or worse, hundreds of tiny white specks show throughout the print area where the white underbase peeks through the colors.
When a print feels rough, it is almost always caused by a screen with poor tension. A tight screen will give you a crisp, sharp image with a smooth surface. And on a manual press, a tight screen will cause far less printing fatigue during the process.
Screen printing… it’s all about the screen. Write that down!
Terry Combs is a 30+ year veteran of the screen printing industry. He is an industry teacher and consultant through the website TerryCombs.com, offering hands on and online classes. And, he is the owner of the screen printing supply company, GarmentDecoratingSupply.com.