How to Take a Bow Out of a Piece Of 3/8 Plywood

Plywood warps, or bows when the grain on one side shrinks due to heat or a lack of humidity. Elongating the grain on that side is the key to straightening the plywood, no matter the thickness. You can press it flat and force it to straighten temporarily with enough weight, but this is unlikely to provide a permanent fix. Altering the humidity of the side the sheet is curling toward will straighten your plywood and keep it that way. Applying heat on the opposite face will speed up the process.

Towels
Hose
Black plastic
Cinder block
Sander

Instructions

- 1
  Wet towels and wring them out so that they are just barely damp. Lay enough of these damp towels out on a sunny driveway, or other flat surface to cover the sheet of plywood you are trying to straighten. Allow the towels to heat in the sun for a half hour. Dampen them with a light sprinkle from a hose if needed. Leave them until they are warm to the touch.
- 2
  Lay the plywood directly on top of the towels, with the curve in the middle going up, in full sun. Center it on the towels. Placed dry black plastic on top of the plywood and place a cinder block in the center of the plywood to press it down. Leave the plastic in place to allow the plywood to heat until the plywood levels out. Remove the cinder block. If the plywood bows up, leave it under the plastic, if not the bow has been cured.
- 3
  Remove the black plastic once the plywood is no longer bowed. Move the plywood indoors to dry in room temperature, so that the heat from the sun doesn't cause it to bow in the opposite direction from drying too fast. Allow the plywood to dry thoroughly. Sand the plywood with 150 grit sandpaper to smooth any grain that was raised by the moisture. Cut the pieces you need from the plywood. Use the technique again if any curvature returns.

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