Q: A job we sanded was first “popped” then stained. After the first coat of poly I noticed bubbles coming out of certain boards. And the bubbles only seemed to be coming out of the soft grain. I did a light sanding and put on another coat of oil-poly satin and had the same issue. This time these were different boards. There were about a total 4 boards with this issue. It seemed like the grain was rejecting the poly. They were BB sized bubbles.
I fixed these boards now everything is OK. I was wondering why this could have happened. Conditions were mid-60s with all windows closed. Applied with a roller.
A: Not sure. If you had left them, would the bubbling have settled down? If this was a re-sand it is possible there was some sort of contaminant in the soft grain that was dancing with the polyurethane. There are plenty of technically strange events in the flooring trade. We all get a turn now and then.