Maintaining wood's flatness, or restoring it when it becomes unflat, is a common woodworking challenge. While preventing wood from warping involves controlling moisture and stress, methods exist to correct wood that has lost its flat shape.
Wood can lose its flatness due to changes in humidity, internal stress, or improper storage. When wood becomes warped, cupped, or twisted, you can attempt to restore its flatness through specific techniques.
Methods for Flattening Unflat Wood
If you have wood that is no longer flat and you want to make it flat again, there are a couple of principal approaches you can take, as suggested by woodworking experience. These methods focus on either physically forcing the wood back into a flat shape or removing material to create a new flat surface.
Method 1: Steaming and Weighting
One technique to address unflat wood involves using moisture and pressure to reshape it. According to some approaches, if you want pieces of wood flat, you could try:
- Steaming them: Introduce moisture to the wood, which can help make the fibers more pliable.
- Placing them on something dead flat: Find a perfectly flat, stable surface to use as a reference plane. A surface like a band saw table is often mentioned as a suitable example of a dead flat base.
- Having something weighting them down that is also flat: Apply pressure evenly across the wood using a flat weight or clamps and cauls. This pressure helps to hold the wood against the flat reference surface.
- Leave it for a few days: Allow time for the wood to dry slowly while held under pressure on the flat surface. This gives the wood time to "learn" the new shape.
- See if that makes a difference: After a few days, remove the weights and check if the wood has retained the flat shape.
This method attempts to relieve stress within the wood by temporarily making it flexible with steam and then holding it flat while it dries and stabilizes.
Method 2: Planing or Sanding
If the steaming and weighting method doesn't achieve the desired flatness, or if the warp is too severe, then the only option you've really got is to level the wood by removing material. This can be done through:
- Planing: Using a hand plane or a power jointer and planer to shave off wood from the high spots until a flat surface is achieved. This is typically done in stages, establishing one flat face and one square edge first, then milling the opposite face parallel and the opposite edge parallel.
- Sanding: Using a wide belt sander or other sanding equipment to remove material and level the surface. This is generally less aggressive than planing but can also be used to achieve flatness, especially on wider panels or less severe warps.
Planing or sanding effectively creates a new, flat reference surface by removing the material that is causing the unevenness.
In summary, while preventing wood from becoming unflat is ideal, you can restore flatness through methods like steaming and weighting or by leveling the surface using planing or sanding techniques.
