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Polyurethane raising grain?

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Forum topic by jasonallen posted 01-08-2015 10:43 PM 1277 views 1 time favorited 8 replies Add to Favorites Watch
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jasonallen

175 posts in 1080 days


01-08-2015 10:43 PM

Topic tags/keywords: oak finishing

I have never used polyurethane before. The only finish I have ever used is Minwax brushable lacquer. However, for this project I am using polyurethane because of the high possibility that a glass of water will be left standing on it. I used the same procedure that I have always used with lacquer.

1. Sand to 220
2. Clean with mineral spirits
3. Stain with Minwax
4. Clean with mineral spirits
5. Apply first coat of finish

I used to use a coat of sanding sealer before my first coat of finish but I decided that wasn’t necessary and had good luck without it in the past. This time, with the polyurethane, after my first coat dried I found the grain was raised at least 1/16 inch. I sanded it smooth with 320 grit paper, being careful not to sand off all the finish and re coated. The second coat is doing the same thing. Am I doing something wrong? Do I need to use a sanding sealer in the future? Or is this just expected with polyurethane? It is being applied to red oak. I chose to used water based polyurethane after being told the oil based would have a yellow effect. Will the water based also prevent water rings from glasses?

-- Skill and confidence are an unconquered army.


8 replies so far

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Loren

8295 posts in 3107 days


#1 posted 01-08-2015 10:46 PM

Poly that cleans up with water certainly will. Oil based
poly is getting hard to find in my state. Aside from
the grain raising though I’m finding today’s water based
poly really easy to work with.

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Redoak49

1936 posts in 1448 days


#2 posted 01-08-2015 11:16 PM

I am not surprised that the you had raised grain with the water based poly as I experience the same issue but never 1/16” maybe a 1/64” but never really measured it. I always assume that it will be an issue and need to sand back done smooth after the first coat.

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dustyoldman

22 posts in 705 days


#3 posted 01-09-2015 12:52 AM

To me the problem of the grain being raised on finishes today is that they are water based . years ago I did not have a problem of the grain being raised . You could put a finish on even cheap plywood and the grain was not raised . I made a kids booster stool 50 years ago and used varnish and it still looks good (6 kids 14 grand kids )
you could try to wipe the piece with a damp cloth and let dry and then sand (wiping with the damp cloth raises the grain ) then sand off the raised grain .it has worked for me .

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MrUnix

4203 posts in 1658 days


#4 posted 01-09-2015 01:11 AM

I use the oil-based minxax poly, and do a lot of red oak.. never had a problem with raised grain. But anything with water is going to do so. Also, make sure you are using real mineral spirits, not the ‘green’ stuff that seems to be everywhere these days.. it will raise the grain as well.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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gfadvm

14940 posts in 2150 days


#5 posted 01-09-2015 02:07 AM

Yep, That’s the downside to water based poly for me. Oil based poly and Spar do not raise the grain like the WB does.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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runswithscissors

2176 posts in 1485 days


#6 posted 01-10-2015 12:52 AM

I’ve had good luck with water based acrylic (Deft). The first coat raises the grain, but after sanding that down the subsequent coats merely need a light sanding.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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Fred Hargis

3926 posts in 1953 days


#7 posted 01-10-2015 12:42 PM

I’m puzzled by the second coat raising the grain. Generally, after the first coat is on, the surface is sealed and shouldn’t raise anymore. For the record, that isn’t “polyurethane”. All waterborne finishes (one exception) are primarily an acrylic finish. It seems like the word “polyurethane” has some magic in the marketing of finishes, so the manufacture’s added a small amount of urethane resin to the can, and put giant letters on the label declaring it “poly”. Back to your issue: I would put on 2 more coats, cut the whiskers back and go from there (at least one more coat). Oh, yeah, the one exception to waterbornes: someone (in the pharmaceuticals industry) figured out how to make actual shellac resins aqueous. So we do have waterborne shellac, since shellac is a common drug coating I guess the aqueous formula has some benefits to them.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Logan Windram

303 posts in 1921 days


#8 posted 01-10-2015 01:21 PM

The first coat of a finish is essentially a sanding sealer. If you are going to stain or dye a piece then apply WB poly, I’d raise the grain first, then sand back of course. After that you shouldn’t have any issues, that is unless you cut the poly with a lot of water to make it thin for brushing…. But the grain should not act up every coat.

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