Heat and moisture tend to be the go-to's for effectively bending wood. Because of the finish, not much, if any moisture will be able to penetrate the wood. Can heat alone, or just a solid rig that provides enough pressure over a long period of time, effectively make a corrective bend to a board after the wood has been finished?

I'm fully aware that pretty much all strategies put the finish at risk, and am hoping for methods that, even if they do some damage can be remedied by some light refinishing without a full strip of the finish prior.

My particular use case is a bookshelf that's got a bit of a warp in it, but I can see other folks having similar issues with any number of projects.

  • In general it's considered that you can't partially refinish polyurethane (once it fails it has to all come off so you can begin afresh). There are no sure-fire ways to correct warping as it is, and the methods really do require unrestricted access to both sides of a board so....
    – Graphus
    Commented Feb 23, 2020 at 8:03
  • BTW no typical varnish application is so effective a moisture barrier that you can consider that not much or any moisture gets to the wood. After all this is how the bookshelf warped in the first place if you think about it. It is possible to effectively waterproof wood with a basic varnish, but it requires a much thicker coat than is usually seen these days (in excess of five full-strength coats, and as many as 9-10).
    – Graphus
    Commented Feb 23, 2020 at 8:05

1 Answer 1


"Effectively"? No.

Theoretically it is possible to bend a piece of wood that has finish on it. However I seriously doubt that the finish would come through the process in an acceptable state. Typically you bend wood by immersing it in a steam bath to both saturate the fibers with water and heat the wood. I don't think a typical poly finish would survive either the saturation or the heating without serious damage.

There are industrial processes that bend wood without either heat or steam, but they rely on immense pressure on all sides of the material. It would be totally impractical to recreate something like this in a hobbyist setting, and even if you could I suspect that the pressures involved would mar the finish. (Frankly, I think the pressure on the wood in a typical steam bending rig would likely mar the finish too.)

Even if you could bend finished pieces the processes used to bend wood are not consistent enough to ensure a totally flat board when you're done. When you release your wood from the bending rig it will not stay exactly where it was clamped. This is known as "spring back". Even if you do a test run to determine how much spring back to expect and account for it in your bending rig it can vary widely from one board to the next.

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