A Method for Correcting Warps

A Method for Correcting Warps

correcting warps

A typical pine board with inadequate kiln drying, so it shrunk and cupped on the outside of the rings as it dried more.

In my last blog post I wrote about the real cause of warps (compression shrinkage) from the continuous wetting and drying out of one side of the wood, whether or not the wood is finished on both sides.

Thinking about this, it may have occurred to you, as it did to me, that it might be possible to correct warps by wetting and drying out the bowed side of the wood. You would cause this side to shrink so the panel would flatten out. So I started experimenting with some warped boards. I shared my experiences with a friend who restores furniture in New England where he sees lots of antique furniture with wide, single-board tabletops. He also began experimenting.

I’m going to describe some of the techniques we developed, but I want to caution that this is a work in progress. We are still learning. We have no hard and fast rules. Correcting warps seems to be more of an art than a science because there are too many variables and no way to have a “control” to compare to. But we have had some successes, and I would say that in all cases we were able to make the warp less than what it was at the beginning.

The first step is to turn the board over so it’s bowed on the topside.

Then thoroughly wet this side with soaking wet cloths to make it swell.

To encourage compression shrinkage of the bowed side, you can add clamps.

Keep the board clamped while it dries thoroughly, which takes many days.

When the wood has dried thoroughly, it should have flattened noticeably.

This is the board after more than a year. The warp doesn’t come back.

You may be able to encourage the flattening by adding weight to the bowed side.

My friend has also tried adding steam to the bowed side to deepen the moisture penetration.

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