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polyurethane AND stain both sides or just poly?

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Forum topic by skogie1 posted 09-02-2014 12:17 AM 1799 views 0 times favorited 5 replies Add to Favorites Watch
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skogie1

95 posts in 823 days


09-02-2014 12:17 AM

Newbie question: I’m finishing a douglas fir table top and I’m wondering if I need to use both stain on poly on both sides to prevent cupping or can I skip the stain on the underside and just poly? Thanks in advance!


5 replies so far

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skogie1

95 posts in 823 days


#1 posted 09-02-2014 12:20 AM

that should have read “stain and poly on both sides” not “stain on poly…”

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Logan Windram

303 posts in 1921 days


#2 posted 09-02-2014 12:55 AM

Oil based stain will not change the way, or rate the wood takes on or releases moisture… So oil based colorant on one side does not matter, I fact, why waste product!

As far as poly, oil based poly should not make your top cup. Oil will not be absorbed by the fibers in the wood, so theoretically you should get no expansion of one side over another. Now if you used a water based dye, or water based poly, you will most certainly see it cup, in fact, I am often shocked by how much it does… But, let that water completely dry on the side you applied, and that cup will resolve natural as the wood finds it’s equilibrium.

IMHO, you don’t need to finish both sides of a table top no matter what you use… However, there are some people who feel feel finishing both side with a finish that give you consistent water moisture absorption/ release will keep that top flat… If your worried, apply finish to both sides.

Good for you to tackle a project, the fun has just begun. Remember, no matter what you do to this project, it important you have fun and learn…

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skogie1

95 posts in 823 days


#3 posted 09-02-2014 01:31 AM

Thanks! Speaking of learning… I lightly sanded the first coat of poly with 220 and it left scratches. What did I do wrong? I sanded the next coat with 320 but I still can see some of the scratches left by the 220. Thoughts?

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Logan Windram

303 posts in 1921 days


#4 posted 09-02-2014 01:44 AM

Nothing, poly is a finish that melts into the last, scratches will be filled in by the next coat of wet poly. You should not be able to see the 220 scratches unless the are very deep…. Meaning the leave a depression in the next coat.

In fact, when rubbing out a table top I often start with 220 to hit the highest spots, the moving to 320 to completely flatten the top. Then, steel wool and lube to a satin sheen.

I would try 400 between poly coats, make sure it is really dry, remember, you are sanding only for a mechanical bond… In fact, I don’t sand in between if it is less than 24 hours before each coat. Most manufacturers say sand if the surface has cured longer that a day, or if you have a bunch of air bubbles… Dust nibs, I just use a brown paper bad on the surface.

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skogie1

95 posts in 823 days


#5 posted 09-02-2014 02:43 AM

Great advice. Thanks a lot.

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