This glued up panel couldn’t breathe on the bottom since it was flat on a table. The top dried out a touch after processing and the panel cupped.
This glued up panel couldn’t breathe on the bottom since it was flat on a table. The top dried out a touch after processing and the panel cupped.

Keep an eye on the panels and check them regularly. With a hair dryer you will probably end up propping it up in a position to blow on the panel and check it every thirty minutes. In the sun, check the progress every hour. If you just move them to a drier environment, check them once or twice a day. Even with regular checks it is not uncommon to go too far and overcorrect. If you let the wood bake too long on one side and it starts to cup the other way, just flip it and dry the other side. Eventually, you will get a feel for how long it takes and end up with a flat panel, and now a drier panel (both good things).

Follow these guidelines for flat wood:

  1. Build with quartersawn lumber. Quartersawn wood doesn’t cup.
  2. Store lumber in the rough. If the lumber goes wonky you will still have extra thickness to machine flat.
  3. Store lumber and build in an environment similar to where the piece will end up.
  4. Quickly build with lumber after it is machined. Don’t give it a chance to move on you.
  5. If you can’t build immediately, store wide boards and panel glue-ups properly. Give them air on all sides or no air at all.
  6. Make sure assembled furniture stays flat by finishing both sides of solid wood panels the same. This is especially important on wide glue-ups like tabletops.

Remember, wood moves and changes size all of the time. It is your job as a woodworker to understand how these changes happen, how to prepare for them and how to control them. And, luckily, in the case of wide wood, you may even have the chance to correct them.

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