4th Coat and fish eye bubbles

Q: I sanded my floors, then put 2-3 coats of poly on them. I decided I wanted another coat-that was done about a month ago.. fish eye bubbles all over the place now!

I don’t want to have to rent another sander (it’s a huge fuss in an apartment building). This is a very small floor space. A pro tried to get rid of them by putting another coat of poly on-a colleague of his told him this might or might not work-it didn’t! I would love to get rid of the fish eyes for once and all.

A: I would let this coat dry for a month. Rent a polisher and use 180-220 grit screens to “grind” the finish and bubbles down. When applying top coats, it is best to make sure the environment is very clean, no air movement for several hours after application, and try to avoid direct sunlight hitting the finish….all this to prevent it from setting up too quickly.

A polisher doesn’t really make any more noise than a whooshing sound. It shouldn’t disturb anyone.

Follow-up Q: Since I might be doing this work myself, as opposed to hiring someone to do it for me, would you be able to tell me how heavy a polisher is to push on the floor, and what is a grit screen? The floor was very clean and the only air movement that took place was the air coming out of 2 windows-no fan was on or A/C. Could this have had anything to do with the amount of humidity of the air outside and/or the temperature outside? I would like to remedy this problem without spending a lot of money on doing so. Do you think letting this sit/dry for a month might do? The layer that got me the fish eyes was done about 2 weeks or so ago and then another layer of poly was put on that to hopefully remedy that one, about a week and a half ago. So, you think I just sit with it for another month?

A: Screen mesh abrasives are discs that are rated similar to sandpaper. the higher the number, the finer the abrasive. You don’t want to be buffing or scratching a fresh coat of polyurethane with a rough abrasive.

The factor humidity has with a typical omu is that the higher the humidity, the slower drying. However, air blowing across a fresh coat of finish can cause it to set too fast, and hence, not flow and level properly. Even the applicator used can be a factor. For example, a roller can tend to inject bubbles into the finish.

The reason I say to wait? You have how many coats of finish on the floor? 5? A typical finish cures by solvent evaporation. If you pile on too many coats, how can the solvent escape? You may end up with a very tender finish that stays soft for months because the solvents have been locked beneath the surface due to multiple coats. Let the coats you have fully harden, then try again.

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