Learn How To Screen Print With Catspit Productions, LLC
Proper Mesh Tension: Getting Better Stencil Performance
Mesh tension is a very important factor in stencil performance and thus print results. This is one of those technical aspects of screen printing that many beginners and even experienced screen printers often overlook or misunderstand. In order to learn how to screen print, it is best to learn and understand the basic technical aspects of screen printing. This will help you to achieve you goals with reasonable effort. Understanding how mesh tension affects your printing is important.
The tension of your mesh will directly affect many aspects of the actual printing. Definition and detail are related to mesh tension. Stencil wear, ink flow and performance, as well as registration can be affected in a negative way with poor mesh tension. The tension of the mesh also has an impact on the physical characteristics too.
Factory mesh specifications are given with the assumption of unmentioned mesh. But in the print shop we use the mesh under high tension situations. As the screen printing fabric expands with increased tension the mesh geometry is modified. Mesh count decreases with increased tension while mesh opening increases with higher mesh tensions.
As you may already know from reading other Catspit articles, this will directly affect ink flow and performance. That is why we choose different mesh specifications in the first place. It is also important to remember tension should be equal in both warp, (long ways), and weft, (crossways), directions otherwise mesh openings may not be uniform in their physical shape, this becomes more important when you get into printing fine lines, 1 color halftones, duo tones, and four-color process work.
Mesh manufactures do provide specifications on ideal mesh tensions but they tend to be very limited in range. A tool called a "tension meter" is used to measure the tension of stretched mesh in units of Newtons. This is a measurement of resistance and the meter readings show how much the mesh deflects under a specific weight, usually being the weight of the meter itself.
- Using under tensioned screens usually requires higher off contact distances which will cause the manual printer to have to push harder to print. This can cause premature fatigue over longer print runs.
- A poorly tensioned screen also poses coating problems for emulsion. Proper mesh tension during coating will give better results.
- Flexing of the stencil on under tensioned screens during printing will also cause premature stencil wear. Cracks and pinholes through which ink may pass can form easily with low mesh tension.
A tight screen will also produce better print quality. Combined with proper off contact, tension will also improve the flow characteristics of the ink and provide for a smoother surface on the printed ink. Good tight screens will also result in better print consistency and even reduces ink consumption.Poor tension in your mesh will give you registration problems in addition to the above mentioned difficulties. This is a good reason alone to use a nicely made screen. With lower tensions stencil drag is exaggerated due to the higher pressures needed to print.
Often the stencil will move excessively in the direction of the stroke. This can cause severe blurring and the increased off contact needed for low tension stencils will also produce significant registration problems.
Needless to say a square and rigid frame is required to achieve and maintain reasonable tension. But the efforts taken to ensure proper mesh tension and frame quality will result in the ability to produce consistent results with relative ease. The importance of this cannot be understated especially in the long run. Check with your screen printing fabric vendor for recommendations on proper mesh tension.
Many beginners think that they can save money by making and/or stretching their own screens. This is a very common mistake to make for printers starting out. Screen stretching is a completely different aspect of screen printing requiring a different set of tools and skills. Stretching screens also requires a certain technical understanding of the process in order not to waste expensive mesh and achieve the desired results.
The cost of pre-stretched screens today also makes it very economically practical to purchase new aluminum screens with mesh tensioned between 20 to 25 Newtons. They are available in various mesh counts and are light weight to ship. The screen will easily last long enough to pay for itself. A few very simple precautions can be taken to ensure the maximum life of a screen.