Keeping bubbles out of brush on poly

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Forum topic by TheWoodenOyster posted 02-21-2014 05:16 PM 842 views 0 times favorited 23 replies Add to Favorites Watch
View TheWoodenOyster's profile


1053 posts in 683 days

02-21-2014 05:16 PM

Topic tags/keywords: finishing polyurethane

Hey guys,

Do y’all have any tips for keeping the bubbles out of brush-on poly finish. I expect to have to sand out some nibs and such, but it seems like the bubbles should be avoidable. Can I fix this by diluting the poly?


-- The Wood Is Your Oyster

23 replies so far

View nailbanger2's profile


968 posts in 1892 days

#1 posted 02-21-2014 05:23 PM

The only tip I can give you is never shake the can, always stir. I would imagine diluting the poly would help, as in making a wipe on poly (50/50) poly to mineral spirits.

-- Wish I were Norm's Nephew

View CharlesNeil's profile


1170 posts in 2619 days

#2 posted 02-21-2014 05:29 PM

is this a oil base or water base

View bandit571's profile


7488 posts in 1431 days

#3 posted 02-21-2014 05:31 PM

Most of the bubble will settle out. Keep brush strokes to as few as you can. The more you brush it, the more the bubbles appear.

Also helps to keep an old T-shirt around. Just when the poly is just tacky to a fingertip, start rubbing the surface HARD with the shirt. You are creating friction, so the harder you rub, the better. This will polish the poly up. It will also help get rid of what few bubbles remain…

-- A Planer? I'M the planer, this is what I use

View mrjinx007's profile


1828 posts in 516 days

#4 posted 02-21-2014 05:32 PM

If you are using foam brush (recommended), the bubbles normally appear as the result of the strokes being too fast. Try applying at a slower pace.


View Knothead62's profile


2364 posts in 1709 days

#5 posted 02-21-2014 07:17 PM

mrjinx007, I just finished a piece of wood to fill in a space over our new dishwasher with gel stain. Got bubbles with a foam brush and had to use 0000 steel wool to smooth it. Applied a poly over the gel stain. Looks great! Will keep your advice in mind in the future.

View bigblockyeti's profile (online now)


1799 posts in 469 days

#6 posted 02-21-2014 07:30 PM

Go over the wet finish with a torch flame or a powerful heat gun. Can’t remember where I read this a very long time ago, but it’s worked for me with both oil and waterborne poly.

View Richard's profile


1103 posts in 1438 days

#7 posted 02-21-2014 07:35 PM

The torch or heatgun trick is used alot when doing epoxy for bar tops and when embedding items like bottle caps or coins into the epoxy.

View Sandra's profile


4985 posts in 823 days

#8 posted 02-21-2014 07:40 PM

I just did a finish with oil based varnish and the foam brush worked great. I was getting too many bubbles with a bristle brush as well
-stir, don’t shake
-smooth passes without pressing too hard.

-- No, I don't want to buy the pink hammer.

View distrbd's profile


1305 posts in 1195 days

#9 posted 02-21-2014 07:44 PM

I haven’t try this my self but I have hears co2 will burst the air bubbles ,so if you breath on the surface slowly it should work.

-- Ken from Ontario

View TheWoodenOyster's profile


1053 posts in 683 days

#10 posted 02-21-2014 07:49 PM

Thanks for all the tips guys. I’ll be trying some of these out

-- The Wood Is Your Oyster

View Jim Finn's profile

Jim Finn

1745 posts in 1670 days

#11 posted 02-21-2014 08:58 PM

Thin it and wipe it on.

-- In God We Trust

View ferstler's profile


333 posts in 2268 days

#12 posted 02-21-2014 09:22 PM

I have brushed and the trick is to brush it right, quickly, and then quit brushing. Also, as has been noted, do not shake the can. Stir slowly. I have also used 0000 steel wool and I may just try that heat-gun trick. Use a good brush, too, needless to say. However, I still prefer spray.

Actually, I would prefer to use spray-on lacquer over either of those two. You do not have to sand between coats and the stuff dries fast and you can recoat in short order. Admittedly, the varnish poly is a bit tougher than lacquer. Pros like lacquer because of the speed, but I also like it because you do not need to sand between coats.

Howard Ferstler

View CharlesA's profile


1929 posts in 546 days

#13 posted 02-21-2014 09:25 PM

This is on the of the reasons I stopped using brush on poly. Wiping varnish is your friend.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View mrjinx007's profile


1828 posts in 516 days

#14 posted 02-21-2014 09:36 PM

Knothead62, They should re-name poly to poly-pain. I would not follow the instructions on the can. I have been doing most of my projects posted on LJ’s with poly and am comfortable with it now. But so many problems at first; watching CharlesNeil’s video helped me a lot in that I realized I was sanding the surface too soon instead of letting it cure for a week or so.


View Rick's profile


7312 posts in 1781 days

#15 posted 02-22-2014 12:44 AM

One of the Main Questions has yet to be answered. Is it WATER or OIL Based Poly You’re Using. I use water based Poly all the time and never have a problem with Bubbles

As mentioned above NEVER shake a can of Water Based Poly, Bubbles Galore and a Bad Finish will result.

As it tells You NOT to do on the can …”They should re-name poly to poly-pain. I would not follow the instructions on the can.” ..... Why do you think they put them there?? To NOT Follow? Then you say you are now using Poly? Obviously you were not doing it correctly before.

I use Flecto or Minwax Poly and Overnight is more than ample for drying time. In fact those types of Polys dry to Quickly, and as also mentioned above, put it on fairly Thickly, then a Quick Brush Out and Leave it alone!

I also use 000 Steel Wool between coats, with a good wipe down and I also vacuum to make sure I get all the little Steel Hairs/Pieces out of there.

I’ve tried the Foam Brushes without much success, they did seem to create Bubbles, so I went back to a Good Quality Natural hair brush. That gets a GOOD, Vigorous, Soapy, Wash and Dry after use. A couple of them I’ve been using for a Year or so now,

-- How long is a Minute? That depends on which side of the Bathroom Door You're On!

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