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I have a piece of pine I want to use for shelving. I added some finish and then added a thin layer Minwax Fast-drying Polyurethane (clear semi-gloss) with a foam brush. It looks great, but the wood now has a coarse texture to it.

I've never done this before so I'm guessing I screwed up somewhere or am using a bad brand of polyurethane... or maybe just need to apply more coats.

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    Sounds like the poly might have picked up some dust. Try "sanding" its surface with a piece of kraft paper (for example, a piece of a brown paper bag), which is just abrasive enough to polish the surface. If that doesn't do the job, you may need to consider a light going-over with a slightly more aggressive abrasive (still extremely fine, such as 000 steel wool). But yes, the more usual practice is to build up several thin layers of poly, sanding very lightly (and removing the resulting dust!) between layers... then do the final polishing. – keshlam Jul 20 '14 at 22:23
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First of all, I'm assuming you already sanded the surface smooth enough before you started. If you put polyurethane on a rough surface you will get a rough finish.

Second, as @keshlam says, make sure there is no dust at all on the surface before you apply the finish. A slightly damp cloth can help pick up anything remaining (but make sure the wood is dry before you apply). Also, don't bother trying to apply a finish in a dusty environment, that's just asking for frustration.

Another possibility is that you kept brushing over the finish as it dried, which is a common beginner mistake. Moving quickly, do a thin coat over the surface and then don't go back to touch it up. Small bubbles may form on the surface as air comes out but it will be OK. If you keep re-brushing over the finish as it gets tacky you will leave the surface rough.

Finally, your chosen brand (Minwax) is perfectly fine, so no particular concerns there. If the can has been sitting a while make sure you stir it before using, but don't shake. You don't want to introduce unnecessary air into the poly.

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    Related tip: In addition to not reworking the finish, one of the simplest ways to avoid introducing bubbles is to use neither a traditional brush, nor a foam brush, but an appropriately sized "painting pad". These fuzzy sponge squares work surprisingly well for applying varnish, though they have some tendency to drip at the edges of the board. With some practice, they seem to be almost as fast, and put down almost as pretty a coat, as HVLP sprayers -- for flat surfaces, anyway. (Woodworking magazine tip; I've learned a lot from 'em.) – keshlam Jul 21 '14 at 1:39
  • Good tips. I think what I did was brush over the finish as it dried. So I'm planning now to sand it down a little and try the painting pad on it you mentioned. – jhawes Jul 21 '14 at 2:47
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    I usually use a foam brush, with good results. The trick with foam brushes is to not squeeze them—just dip them in the can and then dangle to drip off a little, don't drag them across the can edge. That's a sure way to introduce air bubbles. – Hank Jul 21 '14 at 3:51
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The first coat of finish will raise the grain of the wood, so you need to sand it down with some sandpaper (220 grit or so) before you put on the next coat.

This is mentioned in the directions.

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In addition to the excellent advice above, for soft woods like pine it is often necessary to raise the grain before applying a finish for smoothest results.

  1. Sand smooth and using a tack cloth to remove the dust
  2. lightly spray the surface with a little water from a spray bottle, and/or wipe the surface with a damp cloth. Don't soak the surface, just damp.
  3. Let stand for a while (a few hours to overnight, depends on ambient humidity). When you come back to the wood, the surface may feel fuzzy as the individual wood fibers swell and stand proud of the surface.
  4. Now knock it back down to flat with a very fine sandpaper and tack it again. Let dry, and apply your finish.

On rare occasions you'll need to do this more than once.

protected by Community Oct 28 '17 at 17:28

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