# Polyurethane finish - help!



## Schechner (Oct 13, 2009)

I finally finished staining my desk and dresser (both made of cherry) and put the first coat of polyurethane on. It's the Minwax high build stuff. I read in one of my handyman magazines (can't remember which) that for a glass-smooth finish to put the poly on the large, flat areas with a roller, don't overwork it, and use the wipe-on poly for the small areas.

Well, I used one of the foam "ultra smooth finish" rollers, and I got air bubbles. Lots and lots of them. I can't say it ruined the finish, but it's sure as hell close to ruined. When I built a bookshelf a few months ago I used a regular paint brush to brush the poly on, and that gave a much smoother finish, but the brush strokes were slightly visible.

Help! I bought some foam brushes to try. I've used some 0000 steel wool after the first coat to try to smooth it down, but that leaves a ton of steel shavings all over. I wiped them down with some mineral spirits and am ready for coat #2.

Any tips? Has the boat left the harbor, or are these pieces salvageable?


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## AxlMyk (Jun 13, 2006)

Sand the air bubbles out and do it again. This time, thin it 2 parts poly to 1 part mineral spirits, (doesn't have to be an exact measurement) and use a camel or boars hair brush.


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## Bob N (Oct 12, 2004)

Good advice from Mike above. I have never found foam and poly to be good companions. I am also partial to wipe on poly over any other method, but that is just me


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## dutchman 46 (May 23, 2007)

I can't say for sure, but the foam brushes sometimes leaves bubbles. It may be the viscosity of the stuff, or what, but i think that using the bristle brush leaves a nicer finish. Also, DO NOT SHAKE the poly, or the bubbles are going on the surface of your project. If you are brushing, you will have better surface. For a great finish, use a wipe-on for the last two coats, and you can sand, and polish the surface if you just brush. If you sand it down, be carefully that you don't go through the poly, It is better to sand in a random pattern and make sure that the sanding is uniform and do it a second time if necessary.


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## TwoSkies57 (Feb 23, 2009)

Adam, I've got to swing with Howard on this one. you can't beat a good poly brush. I have had good luck with foam brushes but found that I have to be very carefull not to put too much pressure on the brush. I think this kinda acts like a sponge. Squeeze it and bubbles appear. Lightly dragging the foam brush across the surface seems to work fairly well. As for your probject, Definately not a biggie. More of an aggrivation at this point. A good sanding between coats, wipe em down and then 2, 3 or more coats of a good wipe on poly should give you a great finish. I personally really like the minwax wipe on polly, just takes quite a few applications to build it up...


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## AxlMyk (Jun 13, 2006)

As I understand it, wipe on poly is nothing more than regular poly thinned with mineral spirits.


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## jerrymayfield (Sep 25, 2004)

You are absolutely correct. From about 25-90 % depending on who does the thinning. The average is about 50%.

Regards
Jerry


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## jerrymayfield (Sep 25, 2004)

Schechner said:


> I finally finished staining my desk and dresser (both made of cherry) and put the first coat of polyurethane on. It's the Minwax high build stuff. I read in one of my handyman magazines (can't remember which) that for a glass-smooth finish to put the poly on the large, flat areas with a roller, don't overwork it, and use the wipe-on poly for the small areas.
> 
> Well, I used one of the foam "ultra smooth finish" rollers, and I got air bubbles. Lots and lots of them. I can't say it ruined the finish, but it's sure as hell close to ruined. When I built a bookshelf a few months ago I used a regular paint brush to brush the poly on, and that gave a much smoother finish, but the brush strokes were slightly visible.
> 
> ...


If using an oil based varnish the two most common methods of application are
a good natural bristle brush or a soft rag(or blue paper towels). Thin the first layer 10-50 %,follow with unthinned for the next coats. If it is poly-varnish sand between coats. I think it is a bad idea to ever use steel wool between layers of finish.

Jerry


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## Bob N (Oct 12, 2004)

Thanks Jerry.... your finishing advice is always sound


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## Schechner (Oct 13, 2009)

Thanks for all the advice. I can't remember where I read about using the 0000 steel wool between coats. I used that when I finished a bookcase last year, and it worked great (though the tiny steel shavings it produces are a pain to get rid of). It certainly wasn't my idea! I don't want to sand the entire first coat of poly off...I'd be afraid of ruining the piece completely. I'll try just sanding it smooth (I have some 500 and 1000 grit wet/dry sandpaper) and basically start over. *sigh*

My next question is how to clean the brushes after use - I can't seem to find a good source on this. For my bookcase I basically used a new brush for every coat, and that got expensive.


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## curiousgeorge (Nov 6, 2006)

Schechner said:


> Thanks for all the advice. I can't remember where I read about using the 0000 steel wool between coats. I used that when I finished a bookcase last year, and it worked great (though the tiny steel shavings it produces are a pain to get rid of). It certainly wasn't my idea! I don't want to sand the entire first coat of poly off...I'd be afraid of ruining the piece completely. I'll try just sanding it smooth (I have some 500 and 1000 grit wet/dry sandpaper) and basically start over. *sigh*
> 
> My next question is how to clean the brushes after use - I can't seem to find a good source on this. For my bookcase I basically used a new brush for every coat, and that got expensive.



 It would stand to reason that if you use Mineral Spirits to thin the medium, then that would be what you can use for cleaning your brushes. Don't you think?


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## ventura II (Nov 4, 2009)

Adam,
Mineral Spirits is used to thin varnish while paint thinner is used to clean it. Also your expensive car wet/dry sand paper is not clog up and you will not get anywhere. Instead try 3M's sandblaster or Norton's 3X sand paper 220-400 depending on how deep the bubbles are. Good Luck.


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## dutchman 46 (May 23, 2007)

I have used lacquer thinner on the hard to clean brushes, You must use caution to clean the brush with soap and water and make sure that it is totally dry., Don't get near the poly with lacquer thinner. It will take the finish off the brush as well, so only on bristles


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## jerrymayfield (Sep 25, 2004)

Bob said:


> Thanks Jerry.... your finishing advice is always sound


Thank You

Jerry


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## Schechner (Oct 13, 2009)

In response to George - I soaked the brushes immediately after using them in mineral spirits, and they seemed clean...until the spirits evaporated, leaving me two nice, hard, useless brushes. I bought some "paint brush cleaner" which is supposed to solve this problem, but I haven't tried it yet. I'll let y'all know if it works.

As for the finish, I used the 500 grit wet/dry sandpaper and got it _silky_ smooth. I didn't sand it all the way down, so there are a few air bubbles still visible if you look at it at an angle in bright sunlight (which I can do while it's currently in my garage, but I will never have that problem when the desk is in my office). After wiping down with mineral spirits, I applied a full-strength coat of poly with some disposable foam brushes (86 cents for a 10-pack at Harbor Freight!), and when it was dry this morning it was still almost glass-smooth with only a handful of tiny bubbles which should sand right off with some 1000-grit sandpaper. 

I know Howard and Bob advised against using the foam brush, but I found that it worked wonderfully. Sure the foam absorbed a little of the poly, but it didn't affect it. The finish is beautifully smooth and no brush strokes. And the greatest part is the price - about 8 cents each.

For my next project I will definitely thin the first coat. I hadn't tried that.


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## crquack (Oct 10, 2008)

My daughter left me a set of rather nice brushes when she left home. I use them from time to time on various projects. FWIW, this is what I found works keeping them like new:

1) After use soak in Varsol. Get as much paint out of them as possible.
2) Without allowing them to dry wash them in Zep Heavy-Duty Cleaner (Home depot) gradually diluting the bath down with hot water and eventually rinsing with the same.

So far it has worked every time. 

I too had problems with bubbles. Varathane recommend avoiding foam brushes, stirring rather than shaking and not wiping the excess of paint on the side of the can. It works for me - most of the time  But if you have had success with foam brushes, more power to you!


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## Schechner (Oct 13, 2009)

crquack said:


> Varathane recommend avoiding foam brushes, stirring rather than shaking and not wiping the excess of paint on the side of the can. It works for me - most of the time


I never shake the poly (does anyone do that?), and I pour it into a disposable paint tray liner rather than dipping into the can. I've found that if I get any dust or other particles on the brush, dipping back into the can can introduce these particles into the rest of the poly. This way the remainder stays nice and dust-free.

I'm more than pleased with the results with the foam brushes. I'm glad it's possible to clean the brushes, but if I can avoid all that, even better! :yes4:


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## xplorx4 (Dec 1, 2008)

I use wipe on Polly and have had good results. You can, and I do, use the steel wool, I blow the surface down to get rid of the "wool dust". Now that I know it is a thinned down poly, I will be looking into thinning it myself. BTW it says on the wipe on poly can to use the steel wool and to shake it thoroughly. 

Something my brother-in-law explained to me regarding satin vs. gloss finishes. To acquire the satin finish they put impurities in the gloss, such that each coat of satin builds up more and more impurities resulting in losing some of the deep beauty of the wood. He uses high gloss poly except for the last coat then he uses the satin finish.




Schechner said:


> Thanks for all the advice. I can't remember where I read about using the 0000 steel wool between coats. I used that when I finished a bookcase last year, and it worked great (though the tiny steel shavings it produces are a pain to get rid of). It certainly wasn't my idea! I don't want to sand the entire first coat of poly off...I'd be afraid of ruining the piece completely. I'll try just sanding it smooth (I have some 500 and 1000 grit wet/dry sandpaper) and basically start over. *sigh*
> 
> My next question is how to clean the brushes after use - I can't seem to find a good source on this. For my bookcase I basically used a new brush for every coat, and that got expensive.


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