Wood molding does not always go along a straight wall or on a straight frame. At times it must follow a predetermined curve or radius. It might be the railing on a circular staircase or an ornamental mirror. In any of these situations, the wood must be permanently bent to allow for the wood to retain its shape.
Wood has had to be shaped for various architectural purposes throughout history. Originally it was not bent at all but merely cut into the desired angle. Unfortunately, when this is done, the integrity of the wood’s grain is compromised and the result is a total loss of the strength of the wooden member. On the other hand, when the wood is bent and the wood structure and grain is maintained, the strength of the wood is actually enhanced in most situations.
Steam Bending Wood Molding
One popular way to bend wood in general, and lends itself especially to bending wood molding is steam bending. Wood becomes more pliable when subjected to a higher degree of moisture. Hot moisture, or steam, intensifies this effect and makes the process quicker.
The idea is to steam the wood enough to make it pliable, take it out and clamp it into the desired shape or configuration, and then allow it to dry to ambient humidity conditions. This results in the desired molding shape.
Fortunately the process is not hard to tackle with modern materials. What is required is a length of PVC long enough to accommodate the length of stock plus about a foot extra. Also needed are two PVC end caps. Putting these all together will form a steam chamber. A small hole can be drilled in the center of each end cap.
The molding should be inserted into the steam chamber and a steam source attached to one cap. This can be as simple as a length of tubing from a tea kettle to the chamber. At first the opening on the opposite end of the chamber may be closed off until the chamber is saturated. At that point some of the steam may be released to allow fresh hot steam to take it’s place.
Soon the molding will be pliable enough to remove, bend, and clamp. Many times, rather than use clamps, this step may be omitted by simply securing the molding in place with screws or clamps if the moisture will not impact the rest of the project. This may be advantageous since the molding will custom fit itself to the project as it dries.
The Back-Cutting Method of Bending Molding
There are times when molding will be applied where the molding’s back is not visible. In these cases back cutting is a good solution. This method involves cutting small V-shapes out of the molding stock with a coping saw to allow for the stock to gently bend to the desired shape. The “notches” must be equally spaced and the tighter the curve, the closer the notches must be to each other.
When using this method, it is easy to cut, test, and then add additional cuts as needed to achieve desired results. Keep in mind to keep the cuts equidistant. This will ensure a smooth arch.
The main thing to remember when bending molding is to have patience and coax the wood, not force it.