I’m getting to the final coats of oil based polyurathane on my new mesquite kitchen floor. After each coat I sand lightly, shop vac it, let the dust from the vac settle and then use a tack cloth. I’m using a good quality brush and after I work it in I lightly go over that area to get any bubbles out. When it dries I notice little bumps (hundreds) all over. This is OK between coats but what can I do to avoid them for the last coat?
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Replies
Are you using Ploy from a new unopened can? It doesn't take but a couple of days for a can half full of air or more to let little lumps settle out in the can.
Don't ever shake poly in the can. Also don't go crazy brushing it out either, use long slow brush strokes. You might try thinning the final coat some too.
Sounds like bubbles to me too... I'd strain it just to be sure but gently stir (not shake) before your final coat. Also, make sure you wait the specified time before sanding, otherwise you will get little pills of uncured finish.
(Don't ask me how I know any of these things ;) )
PaulB
Beside what's already been said/suggested as the possible causes or cures for the problem, I couldn't help but notice you said you were "working it in". Not sure exactly what that means, but you could be going at this too vigorously which works air into the finish. This has already been mentioned.
Or.......if you're using a fast drying OB poly, it might be that you're taking too long to get back and lay down your final swipes with the brush. This can lead to problems similar to those you describe.
It's also posssible that if this floor was installed a while back and has shrunk during the interim..........you may be sending pieces of sanded finish down those cracks which are just sticky enough that your shop-vac doesn't/can't pull them up......but the fresh poly and the brush do.
You might be well served by waiting 5 days or more before your final sanding/screening to avoid the potential of these sticky buggers being left behind to foul the final coat.
Any chance these little lumps are bits of stuff floating around in the air and settling in your finish?
Edit: Are you cleaning out your brush throughly between coats or just leaving it sit in a can of thinner?
Edited 12/11/2005 7:37 pm ET by goldhiller
Most will go unnoticed, especially once it's scuffed a little with foot traffic. Poly on floors isn't glass smooth since there is always dust floating around. Just look real close at any new poly floor. You can always sand the bumps down with ultrafine wet&dry.
Cheers,
Don
Thanks for your help. I opened a new gallon can to start the project. I gently stirred then and I do for each coat, but I've not noticed much settling since the first stir. But, I stir gently before each coat.
By "working it in" I guess I really meant getting about a two by two ft. area covered then I very gently go over the area by pulling the brush over it at a very sharp angle to straighten brush lines and to remove any bubbles. I installed the flooring myself last month so, of course, there are very few gaps or spaces (although there are a couple butt joints that have "regressed" since I put it in).
I've been using a tack cloth about 30 min to a hr. after I use the shop vac so "stuff" will settle but there could be more "stuff" settling after that, but it is closed up.
I've been carefully cleaning the brush after each use. . . .cost to much not to.
Thinning the last coat and ultafine wet/dry sound interesting. I think I'll google that .
thanks a bunch, everyone.
Fredxpayroll
Sounds like you're following good practice. Only 2 suggestions I have are
1) 30min to 1 hr may be too short, if you can extend that. Depending on conditions, airborn particles can remain suspended for a long time.
2) I've had mixed results with tack cloths, depending on use they load up quick and don't pick up as well. Some finish manufacturers recommend against using tehm. I've switched to clean old rags, lint free, moistened with the solvent applicable to the finish. wipe, expose a clean side, wipe... repeat...
I had simular problem on the last wood floor I refinished. What I realized is the thinner I using on the tack cloth wasnt completely dry on the floor prior to applying the urethane. try giving it a longer drying time.
SB, that's probably a good point. We always have a good breeze. I think I'll open the window for just a minute or two then let things settle for an hour or more before I hit it with the cloth.
SB and Sancho, I thought that a tack cloth was both the store bought type and the homemade type. . . .clean cloth with solvent. My mistake, I've been using the clean cloth with thinner. But, I have not waited for it to completely dry.
So now I'll HAVE to take two more extended oppurtunities to sit on the porch with a good magazine.
Thanks again, I appreciate the help.xpayroll