(Hot/humid summer) air bubbles in finish

Q: We had our floors sanded and poly’d. After 2 coats we had air bubbles in finish. The company came back, buffed and reapplied the poly. Now we have even more air bubbles than previously.

Why has this occurred? Should we have someone else come to fix it? Is this a sign of poor application by the guys doing the job?

A: I don’t know what finish they are using. Typical causes are dirty finish, air flow across the floor before the finish has set up and sunlight through windows. Before applying a coat of finish, it needs to be made sure the floor is clean. No air movement. No direct sunlight. The finish that is used must be clean. I strain my finishes after every job. If I did everything right and still had a problem, I’d probably try a different finish.

Follow-up Q: It has been very hot and humid and the guys opened the windows during application and then shut off the AC. Do you think it’s best to keep the AC on the keep the house cool?

A: I was telling the contractor today that I hate my job in summer. It is a coating nightmare. Air conditioning kills the humidity but can make parts of the house so cold the finish won’t dry. Ventilation is a very good idea. Once the finish has set up, turn the air back on, but ventilate the entire house. Air flow will aid the finish to cure.

Similar Q: We are having our pine and oak floors refinished professionally. After 2 coats were put on, there were numerous air bubbles. So, our guy came to rebuff and put a 3rd coat of poly on. Right away we see the same air bubbles. What should he be doing to remedy this? He blames humidity.

A: I don’t know what type of finish your guy is using, so it is difficult to make anything but general comments. I will say that coating in summer months can be a nightmare for the best of us. Humidity generally causes slow dry times. I would suggest if there are any windows that allow direct sunlight to hit the floor, they be covered. All sources of air movement be prevented until the finish has flowed and set. Then, the best thing you could do is ventilate the area. There is always the outside chance it is his finish. I have a lot of sympathy for people who have coating problems this time of year. The important thing is to find a solution and get the job done.