Stopping the slump

Right at the start we need to kill off a common myth about ink slump. As far as screen printing goes, it has nothing to do with gravity. Our dots and lines are far too small to be affected by gravity and your prints will slump just as much upside down. So if ink slump has nothing to do with gravity, what is the cause? It is simply the tendency of your ink to wet the substrate. If you put a drop of water onto the substrate it might do a variety of things. At one end of the scale, if the substrate is Teflon then the drop will just sit there with no slump (A). However, if the substrate is a very clean glass, then the water spreads out, driven by surface tension, until the drop has become very thin (S). When printing a functional ink onto a typical polymer substrate the slump will be somewhere in between.

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