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Can I put a coat of oil-based poly on top of a coat of water-based poly?

Started by Warbird, March 20, 2015, 05:14:51 PM

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Warbird

I just polyurethaned a bunch of boards with a water-based poly.  It's not looking like what I wanted so I want to lightly sand it, then put on a coat of oil-based poly.

Any harm in doing that?

21incher

I just had the same experience and am going to strip the water base off, sand, and refinish. I think it is the only way to make the finish look good. I don't know why there isn't a warning label on the water base stuff saying you are wasting your time using it. :)
Hudson HFE-21 on a custom trailer, Deere 4100, Kubota BX 2360, Echo CS590 & CS310, home built wood splitter, home built log arch, a logrite cant hook and a bread machine. And a Kubota Sidekick with a Defective Subaru motor.

Warbird

Yeah.  I did some googling and some flooring sites warn that if you're going to do this, to make sure you get ALL of the water-based stuff off, otherwise your finished oil-based poly will have spots that look different.  :(

The wife says I can try another coat of the water-based and just go with it.  Going to lightly sand the first coat with some 220 grit and hope the second coat isn't 'rough' like this first coat was.

Dan_Shade

if it's rough, you're possibly getting dust in it.  you may need to lightly, very lightly, sand the top coat.

you could try a coat of shellac, then topcoat with oil based.

disclaimer:  I haven't tried this, but I understand shellac to be good for this type of thing.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Bill Gaiche

First coat of water base poly will almost always raise the grain of the wood. You will have to light sand before next coat. When my floors were redone they asked if it was oil base or water base. Oil over water base seems to be a no no. You should be able to get a good finish with the water base even if you have to do 3 coats. bg

samandothers

I used some water based poly on a quilt stand.  It turned out ok.  I think I put 4 coats on it with sanding in between. 

Warbird

Thanks gents.  Didn't make it back to the project today.  Will let you know how it turns out.

Warbird

You guys weren't kidding.  It only required a VERY light sanding with 220 grit, by hand.  3 or 4 swipes and it was ready for the next coat.  The second coat of water-based poly went on much better.  Still a tiny bit of roughness so I'm probably going to use steel wool on it now, then do a third and final coat.

Appreciate the advise, gents.

Bill Gaiche


johnnyllama

DON'T use steel wool if it's water base. Particles of steel wool will be left in some of the wood pores and you will end up with discoloration with the next coat. A light 320 sanding will knock of any dust. What wood are you going over?
Turner Bandmill, NH35 tractor, Stihl & Husky misc. saws, Mini-excavator, 24" planer, 8" jointer, tilting shaper, lathe, sliding table saw, widebelt sander, Beautiful hardworking wife, 2 dogs, 2 cats, 23 llamas in training to pull logs!!!

Warbird

Well, too late on the steel wool.  LOL  Haven't put on the 3rd coat yet so will use a damp cloth to try and clean it well.

This is just pine for some trim around the windows.

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