"Steam Bending"

By Bob Reading

Steam or boiling water can be used to plasticize wood so that it can be bent.  The wood can be formed over a mold or form.  After drying, the bent piece should retain its shape.  What is hard to predict is the amount of springback you will get when the wood dries.  The advantage of bending the wood is that the grain will follow the curve and not give you the short grain problem you get with bandsawn curves.  You can also create curves by laminating several thin pieces of wood and gluing them together.   This method is a better way of creating a specific curve from point A to B. 

One of the short-comings of lamination is the time it take to create all the thin strips and all the wood that ends up as sawdust.  Half your wood can end up as waste.   When steam bending you want the grain to run parallel to the length, you do not want grain to have run-out along its length.  Knots and checks are also not good in the wood you are trying to bend.  Breakage may also be a problem; this will depend on the radius of the curve.  If you want to bend 10 pieces you may want to have 12 to 13 pieces ready.

Wood should be bathed in steam for about 1 hour per inch of thickness.  Wood is then taken immediately from the steam box to the mold.  You only have a very short period of time because the wood will start to cool down as soon as you take it out of the steam box.  The wood is forced around the mold and clamped in position until dry.

The steam box should be long enough to hold the length needed and the length needed should be longer than the curve.  Allow extra.  Do not seal the box, as no pressure is required.  Free flowing steam is what you want.  You need holes to let water and steam escape and a rack to keep the wood suspended in the steam.  You need a heater to produce a lot of steam and a container to hold enough water to produce continuous steam for the amount of time required.  A 5 gal. gas can will do but make it a new can and not one that has had gas in it in the past.  You can use a car water hose to move the steam from the can to the steam box.  Do not use garden hose, as it will collapse from the heat.  When selecting wood the best would be green riven wood. The next would be air-dried and the last kiln dried.

When making the bend the outer convex fibers want to stretch and the inner concave fibers will compress therefore a support strap will help in making bend.

Some of the best woods to bend are blackberry, white oak, red oak, magnolia, walnut, pecan, hickory, beech, elm, and birch.  Softwoods do not bend well.  Other hardwoods can be bent, but the success rate my be low.

Try it, you may find it to be fun and it may open up other wood working projects you can try.