Lest you think that I am suffering from severe flatulence I should explain that out gassing is a phenomenon whereby trapped air within a structure forces its way out through a surface coating and mars the finish. So it was when I made a repair to this oak deadwood recently. Before the wood could be painted I wanted to coat it with epoxy to seal the surface. I applied the epoxy fairly early in the morning but we were all set for a hot day and as the wood heated up the trapped air within it expanded and caused the bubbles to appear on the surface (click the picture to make it larger). Normally this is not a problem here in New England as it does often get that hot but we have been having some very high daytime temperatures lately and as the mercury rose to 94 degrees the bubbles appeared.
It was not too much of a problem and wet sanding the epoxy after it had cured got rid of the bubbles but I'll know next time to do this sort of thing later in the day; with the temperature falling slowly instead of rising the bubbles would not have the chance to form as air is tending to be sucked into the wood instead of driven from it. Finally I should add that coating any substrate that contains air such as foam can also produce this effect so be on the look out for it and check the forecast especially if working outdoors.
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