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I've recently built a standing desk out of sandply with a mahogany veneer.

I have stained it, and two weeks ago added a polyurethane clear coat to protect the stain. However, after doing this, the desk is slightly tacky, and things don't slide very well on it.

What can I do to reduce this "stickiness"?

Niall C.
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Malfist
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  • How old was the poly? As they age, finishes can get into a state where they will be reluctant to harden completely. If you're using an old can, it's good practice to apply some to a scrap and confirm that it dries as expected before using it on a real project. – keshlam Feb 09 '23 at 23:41

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The poly simply needs to cure for a while. Even after it "dries" and is safe to work on, the solvents that keep the polymers in suspension aren't all gone; they'll continue to evaporate, and the clear coat will fully harden in time. Check the can for your particular product; it should have a full cure time. It could take up to a month if you laid on a really thick coat and it's humid in your area.

Contrary to intuition, you can wax furniture that has a poly coat, much like you can wax a car that has a clearcoat. Just pick up a can of Minwax, apply and buff, then let dry overnight. This additional protective coating will be temporary, but hard, water-repellent and slick.

KeithS
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  • I finished the desk about two weeks ago. – Malfist Aug 05 '11 at 15:42
  • If it's been humid or you put on a thick coat or the poly wasn't well mixed, that still might not be enough time. – Alex Feinman Aug 05 '11 at 15:45
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    Then I would try the wax. You may also try sanding the poly with an ultra-fine-grit paper (320 or finer), then painting on a second coat. Tack-rag the surface after sanding before putting on the second coat. – KeithS Aug 05 '11 at 15:46
  • I did put on a thick coat. How often would I have to wax it? – Malfist Aug 05 '11 at 15:48
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    Depends on how often you used it and how much contact and friction the surfaces see. The top surface will need waxing more often, and special attention paid to the front of the desk. If you had only waxed it, I'd say about once a year, but since you have a poly undercoat you should be able to let it go longer. – KeithS Aug 05 '11 at 15:57
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    Just to update this question/answer. I wound up doing nothing at all, and the desk is perfectly fine. I guess the finish was still curing. – Malfist Oct 29 '12 at 19:27
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    Update nearly 4 years later. This desk has been through hell and back, with no marring of the poly coat. Looks as good as the day I built it. – Malfist Jun 25 '15 at 18:06
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Poly has a naturally rubbery texture especially if you have a thick coat. You might try sanding with high grit sandpaper to break it up.

Alternately you can put another layer of finish on--something that dries to a hard coat, like shellac.

Alex Feinman
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  • Yea agree - your top coat need to be hard. You might have to apply a 3-5 layers - don't overdo it all at once or you get uneven finish. Patience is a virtue. Layer- wait 30 minutes, next layer.. the more layers the nicer the finish at the end of the day. – Piotr Kula Aug 05 '11 at 15:57
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Oil based polyurethane "dries" in two stages. First the solvents evaporate leaving the resin behind. This normally takes on the order of hours, but as others have mentioned it depends on the temperature, humidity, and thickness of the finish. When the solvent has evaporated the finish will still be sticky. The second stage of drying is cross-linking, where the molecules react in the presence of oxygen to bond with one another. Cross-linking is what makes polyurethane finishes more durable than other finishes. It takes a little longer, but it should not take weeks if the finish was good and properly mixed.

I don't think you have much to lose by trying to seal it with shellac, or even wax, but if that doesn't work then you are left with stripping or sanding back to the wood and refinishing - or put a sheet of glass over it.

Checklist for the refinishing:

  • Is the polyurethane compatible with earlier stain?
  • Are the temperature and humidity within the recommendations?
  • Is it a new can of finish? (check the expiration date before you buy)
  • Stir the can of finish well.
  • Use multiple thin coats instead of one heavy coat.
JayL
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Try to wipe over with water in which a little liquid soap has been added. Subsequently keep wiping with clean water till the coat has no more soap. There is a slight loss of gloss but no more tackiness. Coat with a thin layer of wax after that.

Ashutosh Nath
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Use a little mineral oil and let it stay for a short while. Wipe off with clean cloth till most of the oil has been removed and your work doesn't feel oily to the touch.

Ashutosh Nath
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You applied an oil base finish on top of a water base finish. It won't dry. A fix trick is apply another coat of water base finish on top of it.

Wes
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