Paper, a flat material, frequently with a coated surface, is made out of fibres. In heat-set offset printing a permanent out-of-plane distortion, the so-called washboard effect, occurs quite frequently, which is clearly visible in a lot of web printed products. In the last few decades manufacturers of heat-set dryers have tried to eliminate this washboard by different constructive measures without any real improvement. Views on this washboard have shown a dependency on various physical properties of the web. In printing practice it can be shown that the washboard is caused by the combination of tension, heating and cooling the paper. The washboard occurs when the paper is not flattened when cooled
