Steam Bending, Part I

I prepared a very long description (6,500 words) about steam bending chair parts. It starts with log selection and ends with drying bent parts. Obviously, it is a subject I know a lot about. Thus, I have a lot to say.

I would very much prefer to run the installments consecutively, but that would take five weeks. It seems I always have a lot of timely subjects to write about. So, I decided to excerpt it as I have space. I apologize, as I know anyone starting to follow this blog after I have begun excerpting, will have to rummage around in the archives to find the earlier posts. However, the information is just too valuable to chairmakers to not post because of the problems it creates. So, I start below.

A large number of readers have asked about my shoulder surgery. It went fine, and I am two weeks into the healing. I will wear a very cumbersome and awkward padded sling that immobilizes my left arm for two more weeks. Full recovery is about five months. The injury turned out to not be my rotator cuff. Instead, it was something called a SLAP lesion. I think it is torn tendon at the top of the bicep muscle. There was also some arthritis and a couple of other minor issues.

* * * *

About once a month I receive an email or telephone call very similar to the one below.

“Help! I made the parts for five chairs and steamed them for 45 minutes. I know that’s longer than necessary, but I wanted to be safe.

“The first two pieces broke. So, I steamed the remaining ones for another 45 minutes — an hour and a half! All of those pieces broke as well.

“Only one of the 34 pieces we bent in class at The Institute broke. What am I doing wrong? I am really discouraged.”

When I get one of these messages I feel as helpless as the person who sent it. There is nothing I can do to help from a distance. It is similar to calling the doctor and saying “I have a head ache. What is wrong?” Unless you go to the doctor’s office, he is not able to diagnose your problem either. Unless I am right there with the person having trouble bending; unless I know the history of the wood, I cannot possibly tell what the problem is.

Since I cannot go to the people having these problem, whenever possible, I urge them to bring their parts here and bend them. That way, I can observe their bending technique and be more helpful.

Because so few people can take advantage of that offer, I have decided to write down what we know about steam bending here at The Institute. This information is backed up by 37 years of experience bending many thousands of chair parts, made from hundreds of logs, of about a dozen different species of wood. I am confident you will not be able to find a lot of this information in this level of detail, any where else.

Most Windsor chairs require bent wood parts. It is safe to say that if you want to make these chairs, you have to master this skill. However, steam bending is an art, not a science. No matter how much experience you have, some bendings are going to break. Like a military planner, the chairmaker’s goal is to keep the casualties as low as possible. That means you need to have every contingency leaning in your favor, and you cannot take short cuts. If you do, you may accomplish some successful bends, but your failure rate will be unacceptably high.

Begin with wood selection and use the woods most suitable for bending. About 10 years ago, it was popular for woodworkers to make everything out of walnut. Right now, the “in” wood is cherry. I regularly get calls (as I did then) from people who are suffering very high failure rates. When I ask what they are bending, I am told they are trying to make an all-cherry chair (just as it used to be an all-walnut chair.) This is folly, as these woods do not bend well.

Windsor chairmakers traditionally used locally available oak, ash, or hickory for bendings. These are all ring porous woods with long tough fibers. Today, as in the past, these remain the best woods for this job.

You need to obtain your wood directly from the log. Wood that has been sawn into boards or planks usually does not have straight enough grain to result in a high success rate. Do not buy wood at Home Depot and try to bend it. Do not try to bend wood that has been kiln dried, as wood that has been heated does not bend well. I have had bad luck bending wood that has been heated whenit was left leaning against a wall too near a stove.

You have to be finicky and down right fussy when selecting your logs. When trying to describe to people what to look for I say, “Think telephone poles.” That is just what you want, trees that look like telephone poles, perfectly straight. The wood inside such a tree will generally look like the tree did on the outside. For that reason, the trunk must be straight, with no curve or twist. If there is, the wood will be bowed or twisted.

There must be no obvious blemishes on the log’s surface. A blemish in the log will cause the layers of annual growth to deflect around it, and the stock you obtain will not be straight. Reject out of hand logs with freshly trimmed limbs. It does not matter whether these limbs were live or dead.

Refuse any logs with bumps or burls. Next to the shape of the log, the bark is the best indicator to what is inside. Oaks, ashes, and hickories have coarse bark with striations in it. These should all be straight and parallel.

A knot or defect inside the log is said to be “encased.” Encased defects will usually disturb the pattern of the striations in the bark and often create “cats faces.” These telltale swirls are a sure give away that the log contains a defect, and should be rejected.

Be on the look out for folds in the bark. These appear as long (often dark) lines, like a scar on human skin. These folds cover an injury the tree has sustained. Look out also for dark stains in the bark. This can indicate an injury that is still open to water, which can cause rot in the log.

No matter how choosey you are, there is no guarantee that even the best looking logs will not have flaws. You cannot be sure what the wood looks like until you split it open. If you are buying the log at a mill, you obviously incur all the risk. The saw mill owner is not going to let you return a log that you split open.

Avoid logs that are too big or too small. We do not like them to be less than 14 inches in diameter, nor greater than about 24 inches. Small logs have a greater percentage of juvenile wood – the wood that was once the sapling. This wood usually has too many small encased knots to be good for bending. Logs that are too big cannot be easily handled. Splitting them requires more wedges and back breaking work. In a big log, the splits made by the wedges frequently miss each other rather than running together, and a lot of wood will be wasted.

Here at The Institute, we use forest grown trees. We are a big enough business to be able to buy our logs wholesale from a concentration yard that sells veneer logs to buyers from China and Germany. The logs are delivered here by a big logging truck and a cherry picker. If you want just one log, try a local sawmill or a logger. They also have forest grown trees.

I have successfully used oaks that grew on someone’s lawn. However, landscapers and tree services usually have urban grown trees and I would recommend avoiding these. We tried to use an urban tree in a class I taught in Atlanta many years ago. The log was beautiful, but we had almost 100% failures. I do not know whether the problem was environmental, but I never wanted to take that chance again.

Finally, determine when the tree was felled. If it has been down too long, it may have begun to decay. Decayed or decaying wood will not bend. If you are buying from a saw mill, the operator may not know this information, but if your are buying from the logger who cut it, he should.

Otherwise, your best bet is to examine the sapwood. This is the band of annual rings about an inch thick and closest to the bark. On oaks, the sapwood is usually a lighter color. The sapwood contains nutrients that attract fungi. These will usually appear as bluish or blackish spots about the size of a pencil point.

In red oak, you can cut away the speckled sapwood and still use the reddish heart wood. I suspect the tannic acid in red oak protects it. However, after enough time even heart wood will be affected by decay.

If you would like to receive periodic updates, tips, tool reviews, and new sources, that are outside the scope of this blog, join our mailing list by emailing me at mike@thewindsorinstitute.com