This the third part of a very long explanation and description of steam bending. I cannot run the whole part at once, and too much goes on around here to run it over consecutive weeks. Therefore, I am posting it as I can. If you are only begun to read my blog, you may want to search for Parts I and II and start there. Mike Dunbar.
* * * *
Since Windsor chair parts are bent from the middle, it is necessary to locate and mark the center. You have about 45 seconds to bend a part. While, this is more than enough time, you do not want to be delayed by problems that could have been avoided.
We also mark the centers of our bendings with a Sharpie, as it leaves a dark, easy to find mark. Do not skimp on this important step by making a faint or incomplete mark. Make the center mark all the way around a round part and on all four sides of one that is rectangular. When you take the hot, wet part out of the steam box, you do not want to waste precious time looking for your mark.
Do not use a mechanical pencil or a ball point. Steaming gives the wood a slight gray cast, and the faint mark made by a mechanical pencil can be hard to find. Steaming will bleed ink out of the wood and the mark will disappear.
Remember steaming wood is an art, not a science. Some parts will break, even when you are doing everything right. The goal is to keep these failures at an acceptable level. This means you want to have as much in your favor as possible. The process we use at The Institute does just that. An average of two parts out of 34 will break in a sack back class. In some classes, there are no breaks at all. In others, there are more than two.
In our experience, bending goes better some days than on others. Over the years I had observed this and began to look for the cause. The following may seem like folk lore, but it is quite true and accurate. The best bending days are those that are bone dry and crystal clear. These are the days that make you feel like you have boundless energy. Wood taken from the steam box on these days feels dry and not very hot.
The least favorable bending days are wet, gloomy, and dreary. These are the days when there is not enough coffee in the world to wake you up. Wood out of the steam box feels wet, and is so hot we end up juggling it from hand to hand as we carry it to the bending form.
This observation runs counter to what one would assume. Since wood needs to be hot and wet to bend, it seems a wet day would be our favor. However, this is not.
We found an indicator that would tell us when bending conditions were good. We found it in a very unlikely place — a piece of wood called a weather stick. These are specially cut twigs from Maine that are sold by some of the country living type catalogs for about $8. Please, Google “weather stick” rather than calling me for a phone number.
When the weather is dry and providing a good bending day, the stick points upward. When the weather turns dreary and overcast, the stick turns down. Obviously, the wood in the twig is responding to the relative humidity of the surrounding air, and the particular way it was cut makes it go up and down.
The weather stick further underscores how much successful steam bending is art and skill. I would never recommend becoming a slave to the weather stick. However, if you are not in a hurry and have the flexibility to wait for a better day, I would. At home, you have an advantage in that you can wait for a good bending day. We have to bend on the first day of each class so our parts are dry and ready to use later in the week. Regardless of the weather, we fire up the boxes and go to work.
To successfully bend wood it has to be both hot and wet. The temperature should be at least 185 degrees F. with 25% moisture content. With both these properties the wood is said to be plasticized, which means capable of being bent.
The steam box we use is the one we developed and perfected here at The Institute. We call it The Ultimate Steam Box, because it is so efficient and because it solves the problems associated with other ways of making these devices.
To make the box we use Schedule 80 PVC pipe. (Schedule 40 will not take the heat and will crinkle up like a pretzel.) Wood steam boxes require a lot of steaming time just to become saturated and tight. Unless insulated, metal boxes radiate off a lot of the heat that should be plasticizing the wood. If you touch an exposed part of a metal tube you can get a good burn. PVC is both impervious and a good insulator. I demonstrate this to a class by holding my hand on the PVC tube. Only 1/4 inch away from my skin is live steam.
We boil water on a 160,000 BTU burner originally designed for cooking lobsters and crawdads. This burner creates a rolling boil and lots of steam. Electric hot plates and the camp stoves that I used early in my career, make the water simmer and do not provide the volume of steam created by these new burners.
We boil our water in 5 gallon steel utility cans. Needless to say, we buy these brand new and never put gasoline in them. Five gallon capacity is more water than most chairmakers will need. However, in a sack back class we bend 34 arms and bows in about 2 1/2 hours, and having to continually fill the boilers is a nuisance. For most chairmakers a two gallon can is sufficient.
The steam box and boiler are connected by tight fittings. This ensures that all the steam that is generated in the boiler is conveyed to the steam box. Because the PVC is impervious and a good insulator, the steam goes right to work doing its intended job of plasticizing the chair parts.
* * * *
We heard recently from Sir Chris Otto. Sir Chris wrote to tell us he was working on an order for six sack backs. Also, that order will include his 100th chair. When he is done, he will have 104 chairs under his belt.
* * * *
After my posting about my thoughts of a new approach to selling chairs, I heard from Sir Joel Jackson. Sir Joel said he would try my ideas and keep me posted. I head from him recently. He had just exhibited at a show. He writes, “I posted a nicely printed sign at the entrance to my booth that began “INVEST YOUR INCENTIVE CHECK IN A SET OF HAND-MADE WINDSOR CHAIRS”. I then preceeded to list some of the benefits that you eluded to in your blog.
I had several positive comments, none that were negative. Traffic was extremely slow compared to previous spring shows. However; I did sell a stool, settee, comb back and youth chair. All of those customers had stopped to read the sign. I was reluctant to discuss it with them for fear of interupting the selling process; but, I think it helped. Those that did comment especially liked the concept of the chairs outlasting the length of time to replace the wood with which they were made.
I don’t have another show until Memorial weekend, but will post the sign there and continue to test the waters.
* * * *
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 firstname.lastname@example.org