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Mesh Matters

(June 2009) posted on Wed Jun 03, 2009

The level of detail you can print, the quantity of ink you lay down during the print stroke, and the ability to reproduce an image accurately and consistently are but a few of the print characteristics that are influenced by your screen. Here you


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As the foundation of the screen-printing process, screen mesh deserves some careful study if you want to optimize the quality of your prints. Understanding the makeup of screens, their physical characteristics, and their performance attributes will help you make the right decisions about which mesh to select for specific applications and how to use the fabric to get the best results. The following discussion reviews key points to keep in mind when choosing screen mesh for your jobs.

 

Mesh basics



Screen fabrics are woven from monofilament or multifilament yarns, most commonly polyester, although nylon and steel-wire meshes also are available. Monofilament fabrics are woven from single-filament threads. This thread construction provides predictable and controllable performance and has made monofilament polyester the dominant fabric used in screen-printing applications.

Multifilament fabrics are woven from threads that are made of multiple filaments twisted tightly together. These fabrics account for only a small portion of today’s market because the structure of the yarn does not lend itself to precision thread diameters and edge definition. Although the rough thread surface promotes stencil adhesion, the multifilament yarns are more prone to severe ghosting and are more difficult to reclaim.

Screen mesh usually is offered in standard white or dyed yellow colors. Un-dyed polyester threads reflect and scatter light during the exposure process, thereby causing stencil exposure beyond the image edges defined by the positive image, a condition referred to as undercutting. The result can be dot gain or loss, poor image edge definition, and decreased image resolution, particularly in images with higher halftone line counts and finer details. Yellow dyed mesh, on the other hand, absorbs the UV wavelengths of light that expose the stencil and prevents light scattering, which preserves image resolution and edge definition. The drawback to yellow-dyed mesh is that it requires longer exposure times during stencil production.


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