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Understanding Screen-Tension Loss

(December 2013) posted on Wed Jan 16, 2013

Learn how to identify problems in screenmaking that most often lead to reduced screen tension and how to anticipate and minimize tension loss.

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By Screen Printing's Solution Sourcebook

Gradual screen-tension loss is inevitable, even when you control your screenmaking and press-setup workflows carefully. A variety of factors contribute to screen-tension loss, and several can occur simultaneously, making the culprit hard to pinpoint.

Source vs. cause
Low screen tension is a leading contributor to poor image quality. Improper flooding, poor snap-off, smears, and loss of detail are some of the problems associated with low tension. In addition, inconsistency in screen tension in a multicolor job can lead to misregistered colors, moiré, mesh marks, and image defects.

You can trace screen-tension loss to two primary sources and several secondary causes. Every screen consists of only two principal physical elements: the mesh fabric and the frame. In every case, tension loss stems from one or both of these sources. External factors that lead to weakening or failure of either of the two elements are considered causes.

Wood frames
A properly designed and constructed wood frame will yield an entirely satisfactory print, but wood frames are more likely to cause tension loss than their metal counterparts. Here are some reasons why.

Reclaiming The way wood frames are processed for future use is one of the primary causes of screen-tension loss. Wood absorbs the water and cleaning chemicals used in reclaiming. As a result, the frame is less able to withstand the stress imposed by a tightly tensioned screen.

Beam deflection This condition refers to the tendency of the frame’s longer sides to bend inward. Beam deflection is worsened by the wood frame’s inability to hold its proper shape under stress. Beam deflection occurs to some degree in all frame types, including rigid and retensionable metal frames, but the fact that wood frames absorb moisture makes them most susceptible to the problem. If the wood bends while it’s wet, the frame won’t likely return to its original shape—even after the mesh fabric is removed.

Heat Screens are often dried in heated cabinets or in rooms that are equipped with dehumidifiers, which also create heat. The wood frame’s tendency to bend inward becomes even more pronounced when the frame is hot. Combining moisture and heat further compounds the problem.


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