Whitish patches of polyurethane lifting

Q: I am just applying the second topcoat of an oil based clear polyurethane. The first coat had just over 12 hours drying time. There are slightly whitish patches of polyurethane lifting, appearing from where I’ve gone over the first coat.

They were not apparent prior to applying the second coat. It was well sanded and clean.

A: If you wiped down the first coat with a dampened towel before applying the second, did you make sure the floor was dry before coating?

Similar Q: My living room has hardwood parquet tiles that I sanded, re-stained in spots, and applied 3 coats of Minwax high build gloss poly. Starting 2 months later, areas of “lifting” started showing up. It looks like bubbles of non-adherence, even in areas that receive no wear and tear. I believe that each of the three coats were given more than ample time to dry. It was VERY humid when I did the work. Is this my problem? How can I fix it and how can I prevent it from happening to a second room that I plan to restore? Any help much appreciated.

A: Adhesion issues generally boil down to 2 main issues: contaminants on the floor in the case of buff and re-coats and insufficient abrading of the previous coat of finish before applying another. You may very likely have to totally sand this floor to bare wood again and start over, I’m afraid.