Bending wood transforms solid, straight wood into graceful curves. It’s often an adjunct to another project, such as building furniture, baskets, musical instruments, toys, or crafts. It’s also fun to play around with on its own.
Bending wood is a two-step process: first softening the wood, then forming it. Steam is a good agent for softening wood. Wood can also be softened by creating multiple cuts on the back of the wood. This method is called kerf-cutting.
Bending Wood With Steam
Wood can be soaked in water to soften it. Heating the water above 212 F (boiling) to create steam softens the wood faster. The softened wood is clamped into a frame and left to dry.
You’ll need to build a steam box to hold the wood during the steaming. A steam box can be made of nearly any heat-resistant, waterproof item of sufficient size.
A steam source, such as a steam cleaner, is attached by a hose to the steam box. The steam box must be vented at the top to allow the steam to escape, thus relieving pressure. It also must have a drainage hole (or weep hole) at the bottom to drain off condensation.
After steaming, the wood is placed in a frame that bends it to the correct size. After the wood dries, it can be removed.
Best Types of Wood For Steam Bending
The thinner and smaller the wood, the better it works for steam-bending. Sheet materials are difficult to steam-bend because of their size.
White oak, hackberry, and red oak bend well. Soft maple, yellow-poplar, and hard maple are poor wood species for steam-bending.
Wood is generally bent perpendicular to the direction of the wood grain. Bending the wood parallel to the grain can crack the wood.
Green; no chemicals
Softens all of the wood, not just one side
Bends are permanent
Potential for scalding
Steam box must be built
Must be formed in a frame
Significant waiting time
Bending Wood by Kerf-Cutting
Kerf-cutting requires no soaking or steaming, so no waiting time. Multiple incisions are created in the back of the wood with an electric saw. This makes the wood flexible enough to bend. Even thick wood and large sheet goods can be bent by kerf-cutting.
For kerf-cutting, nearly any type of wood can be used, even composites like particleboard or Masonite.
Try to bend kerf-cut wood perpendicular to the kerfs, if possible. But you can bend the wood parallel to the kerfs, too. Just be careful to bend the wood slowly and carefully to avoid cracking.
No soaking or steaming
No waiting time
Thicker materials can be bent
Requires a miter saw or radial saw
Only one side of the wood can be visible
Creating multiple cuts can be tedious
- Steam Bending: Steam can injure you. Be careful when opening the steam box. Handle only with heavy gloves and use safety glasses.
- Kerf-Cutting: Observe all of the safety requirements for working with electric saws.
Equipment / Tools
- Steam source
- Cordless drill
- Utility knife
- Spring clamps
- Heavy gloves
- Eye protection
- Miter saw, table saw, or radial saw
- Kerf saw blade
- Eye and hearing protection
- Scrap blocks of wood
- 4-inch PVC sewer pipe
- 4-inch PVC sewer pipe solid cap
- 4-inch rubber gasket
- 2-inch hose
- Wood glue
How to Bend Wood With Steam
Build the Steam Box
Attach the solid cap to the end of the sewer pipe. At the other end, attach the 4-inch rubber gasket. With the utility knife, cut a 1-7/8-inch hole. Force one end of the 2-inch hose in the hole. Attach the other end of the hose to the steam source. Drill several weep holes at the bottom and several more at the top to relieve pressure.
Prepare the Steam Box
Remove the rubber gasket. Place the steam box in an area such as a garage or outdoors, where the flooring will not be harmed by excess moisture. Put the boards to be bent in the steam box and elevate them on wood blocks. Replace the rubber gasket.
Build the Frame
Using plywood, lumber, or clamps on a workbench, create a frame for shaping the wood as it dries.
Activate the Steam Source
Turn on the steam source and bring it to boiling temperature. A general rule of thumb is to steam wood for about one hour per 1-inch of thickness.
Remove the Wood
When the wood has finished steaming, remove it immediately while wearing thick gloves.
Let the Wood Dry
Quickly place the wood in the frame. Overbend the wood by about 5 percent because there will be some bend-back after the wood is removed. Let the wood dry for about three days.
How to Bend Wood by Kerf-Cutting
Set the Saw Blade
Adjust the saw blade’s depth to about 1/8-inch less than the thickness of the wood.
Mark the Range of Cuts
Unless you will be bending the entire material, mark the span of the bend with a pencil or painter’s tape.
Make the First Cut
Turn on the saw and run the blade across the material, beginning at one end of the bend span.
Make Subsequent Cuts
Keep making additional cuts, maintaining a distance equaling the width of the saw blade. Continue until you reach the end of the bend span.
Bend the Wood
Kerf-cut wood can be bent by installing it in its eventual installation area. For example, to make a bend in a wall, the panel would be nailed into place. The nails hold the wood’s bend.
Alternatively, you can fill in the kerfs with wood glue, bend the wood into a frame, and leave the glue to dry. This works best for outward wood curves, not inward curves. For inward curves, you’ll need to build a supporting frame in back to hold the bend.
About Bending Wood With Chemicals
Treating wood with a gas created by a solution of 75-percent water and 25-percent ammonia can soften the wood fibers enough to bend them. This method is especially good when you need to bend the wood sharply or create curls.
This method is not recommended for do-it-yourselfers. A tight chamber must be built so that the wood can be subjected to an ammonia gas under high pressure. While it’s a highly effective process, set-up is difficult and the potential for injury is great.