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What happens if you forget to sand between polyurethane coats?

85K views 16 replies 7 participants last post by  wapakfred  
#1 · (Edited by Moderator)
Put on a second coat forgetting to sand it between.

What's likely to happen?

Is it fixable/sandable, or does it "soak" (for lack of better description) into the wood?

Fortunately it wasn't my good piece, just a small trinket box.

Thanks!
 
#3 ·
I think it's highly unlikely to cause any problems.
Respected finishing expert Bob Flexner suggests that sanding between coats isn't necessary for proper adhesion between coats. He (and pretty much everyone else) recommends doing it anyway, mostly in order to get rid of the dust nibs.
See http://www.popularwoodworking.com/article/the_7_myths_of_polyurethane
 
#7 ·
I don't think it would give you any problems, although as others mentioned it is always advised to improve adhesion.

I was finishing some oak slats for a table I welded a few years ago, using brush-on poly. Now, if you have ever finished oak with a brush, you surely won't forget to sand between coats…
 
#8 ·
Oh

So does this stuff run easily?

I laid a cabinet on its' back and gave it a coat, I propped the door open just a little so if it ran it wouldn't glue it shut. With the door sloped a bit is it likely to dry unevenly? I just didn't think it would hurt it because I've done completely verticle surfaces with no problem, they turned out great. It isn't caked on there or anything.
 
#11 · (Edited by Moderator)
Oh wow, so you ll do even more than 2 coats?

- Thomas Anderson

Typically 3-5 depending on the piece, the finish, and the look I am going for. 2 coats is rarely enough coverage.

- jmartel
So what are you using, clear satin, semi, gloss etc?

I'm asking because I was wondering if the clear satin is supposed to be glossy or if its' only purpose was to protect.

Plus a big concern of mine is I have a dehumidifier in the basement, so I know that will be drawing moisture out of the wood for a long time, eventually it'll be completely dry. I'll probably coat the insides too, of everything I make.
 
#12 ·
All of the above. Satin should have a satin sheen to it. That's really the only way to describe it. The photo you posted above looks satin to me.

If you want to knock down the shine a bit, take some #0000 steel wool with a bit of paste wax and rub the wax in. Use little circular strokes and go over the entire box. Then do it again. Buff off the wax with a clean T-shirt/rag and it will be extremely smooth and even.
 
#17 ·
You might get a better response if you start a new post versus dragging up a very old one. But when you "fix", what's the problem. Polycrylic has only a small amount of urethane resins in it (most of the resins are acrylic) and as far as I know it generally isn't recommended to sand between coats (I may be wrong about that, I don't use the stuff). The sanding between coats has one of 2 purposes. One would be to smooth out duct nibs and the like, the second would be to provide some tooth for the subsequent coats (the reason for sanding between coats of an oil base urethane varnish).