[lupo]

Urethane's need humidity and heat to dry. Most paint calculations are based on 70° and 50% humidity. If it was a low humidity day and you recoated too quickly or applied the paint to heavy bubbling will be the result. When the top dries before the bottom layers and bottom layers emit gas causing bubbling in the surface. So slow it down watch the humidity and heat and don't lay it on so heavy.I hope this helps