Coating Terms

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Telegraphing is the revealing of surface of the coated part of the substrate through the coating. Sometimes, the showing through of fingerprints, water spots or sanding marks on the substrate is called telegraphing. But these defects are usually manifestations of dewetting. Telegraphing is normally caused by surface tension gradients on the part of the substrate due to the concentration or temperature changes. For instance, when baking a sheet metal surface, if there is a reinforcment element, it will cause that part to have a lower temperature and therefore a higher surface tension. In this case, due to movement towards the high surface tension region (Marangoni effect), paint film above the reinforcement element will be higher.