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September 25 - October 2, 2015

What causes blistering/crater formation in freshly applied polyurethane topcoats, and how can this be avoided?

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From Sarah Geary of RockTred on September 28, 2015:
A number of things can cause the craters. Blisters are entirely different. Figuring out which it is would help solve your issue, however, it has been my experience that craters in 2K polyurethanes are sometimes caused by air or carbon dioxide bubbles. When you are mixing your 2K together, be sure to not mix too vigorously as you can trap air in the mix. Once the coating is applied, the air will attempt to make its way to the surface of the coating. If the air doesn't move quickly enough through the coating, the surface of the coating will not be wet enough to refill the hole the air bubble has left behind, causing a crater. You will experience a similar phenomenon when applying the coating too thickly. The chemical reaction can create outgassing which creates bubbles of gas similar to the air I mentioned before. It will create similar issues with the surface of the coating. "Blisters" could be a conglomeration of air bubbles beneath the coating, but generally, we figure out how these are formed by gathering information about relative humidity and other application conditions in order to prevent these in the future.

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