This week I continued in my preparation of parts and pieces for the three John (Jennie) Alexander chars I am going to make for a demonstration with my woodworking club, the Brown County Woodworkers. I started a few weeks ago before we went on vacation to South Dakota. Saturday I removed the first pair of back legs from the steam bending form and prepared the second set of back legs.

Since I will be teaching a demonstration I will have all three chairs in various progressive stages of completion so I'm only worried about partially doing the first two chairs now. I will wait on the third chair until later.

The first set of back legs survived the bending process with no problems. I will set them aside until later when I mortise the holes for the back slats. It's easier to leave them in octagons for now until all the steam bending and mortises are cut. It's very hard to do either of those activities if you go all the way to round cross section too early.

After taking the 1st set of back legs out of the form I checked that the next set of back legs were nice and moist. I had left them in a tube of water (plus one cup of downy fabric softener) for the last 2 weeks top down so the top part I will be bending has been soaking up a lot of moisture. Then I fired up the steam bending chamber by hooking up the wallpaper steamer so that it could come up to temperature. It takes 30-45 minutes or so for the steam pressure to build sufficiently. You need it to get all the way up to steam temperature which is roughly 212 degrees.

As the steam generator built up temperature, I started working on the front legs for the first two chairs. These were cut to length and into 1 3/8 inch thick octagons several weeks ago. This Saturday I started by marking the start of the tapers and then drew a mark a little inside the edge of the octagons on the tapered end so that I would have a 1 inch thick octagon instead of 1 3/8 inch thick. The arrows help me remember which axis will face the center of the chair later.

By clamping the end to the bench and resting the end against a stop I have a firm platform to simply use a #4 or #5 smoothing or jack plane from the beginning of the taper to the mark for the 1 inch thick octagon. If you skip every facet you can start by tapering the octagon to a 1 inch square first which is really easy to see when you need to stop by eye. When the edges come together to form a square - stop. I usually count how many strokes it takes so I have an idea where to stop on each facet.

After you go square you then alternate on the other four facets until you re-establish an octagon 1 inch thick. This small taper from 1 3/8 down to 1 inch will create a nice visual taper at the foot of each leg. It's not much, but it really makes the chair look more elegant.

Once the water temperature starts to boil at roughly 212 degrees you start generating a steady flow of steam. It's important that you have plenty of water and that the temperature stays constant so you want the hose going into the steam box, but you also want it to "flow" so it doesn't build up pressure. You need your steam box to be closed tight enough (closed on both ends) so that you don't loose heat, but not so tight that the steam has nowhere to go. You actually want a few holes or a slightly loose door so that steam is constantly flowing through the box. Once you have the temperature constant at 212 degrees and the steam is spilling out of the edges you can put the back legs into the steam box for 1 hour for every 1 inch thick. In this case the part that we are trying to bend is 3/4 inch so anywhere from 45-60 minutes is a good rule of thumb.

You don't want to over-cook your wood or the heat from the steam will actually dry the wood so much it will become brittle and crack. I did that on my first try, and so far it hasn't happened again unless I have to much grain run-out (a weak joint). The steam also brings in moisture, but there is a tipping point so it's a timing issue by trial and error which is where the 1 hour per inch thick rule of thumb comes into play. You can modulate that a bit by species of wood and whether or not it was green (fresh) wood or not, but it's a good starting point.

You'll notice that I keep jumping back and forth between front and back legs as I let the steam generator come up to temperature and then as I wait my hour. That's why you need to think through the sequencing of your operations or you'll be standing around waiting a lot.

When I was able to put the second set of back legs in the steam box top end (moist end) down I started working on taking the cross section of the front legs down from octagonal to circular cross-section. The reason I can do that on teh front legs and not the back legs so early is because the front legs do not get steam bent nor do I need to use a router or chop teh mortises in the front leg. I have a special jig technique I will show later that helps me drill the circular mortises in the front legs and I can go straight to the round cross-section now.

This is actually a very enjoyable part of the process because I get to use the shave-horse and a few simple tools like the spoke shave and and small block plane to generally take off the octagonal corners until I have 16, then 32 sides and then I just round everything over. The only tricky part is to take shallow passes and keep paying attention to grain orientation to determine if you need to either use the tool on the pull or push stroke to avoid tear-out. It's very efficient, and with a bit of small tear-out you get a pretty good cylinder with a taper on one end.

When I was done getting the four front legs to the first two chairs to a generally circular cross-section I then took a sander with 60 then 100 grit to generally smooth them out and remove most of the small bits of minor tear-out. No reason to go any higher at this time. It's still rough joinery at this stage. Once complete I throw these legs into the water bath for a week or two to absorb a lot of moisture.

The magic of these chairs is that each mortise and tenon resists the urge to fail by five important principles of wood joinery. (1) the mortises and tenons are extremely tight as we precision drill the 5/8 inch holes for the circular 5/8 inch tenons. Each tenon is hand fit for a friction (tight) fit. (2) we glue each tenon into each mortise. (3) lots of surface contact. We have 24 individual mortice and tenon joints in the base and 4 in the slats. (4) we do a secret overlapping lock mortise that I will show later by offset drilling every other mortice at a small overlap from the previous mortise to lock the side rungs into the front rungs to prevent racking. And finally (5) we use the natural tendency of wood to absorb or shed moisture to our advantage. To do this we soak the legs that will take the mortices for a week or more before we drill the mortises do the legs are as moist as they can be. Meanwhile we super dry the rungs before final shaping by putting them into a small lightbulb powered kiln for at least a week to slowly dry them out to a much lower humidity than they will every encounter. When we finally shape them and join them together super wet to super dry the tendency of the wet mortise to shrink and the dry rung to expand as they both either lose or gain moisture approaching ambient humidity will literally "lock" the two pieces together for eternity........ But this is a story for later when I get to that part. I'm simply telling you now so you understand why I'm throwing the legs back in the water.....

Okay, by now the back legs for the second chair have been cooking in the steam chamber for an hour and they are nice and limber. It's a pretty quick process, and as a one man shop I didn't take enough photos because steam bending is a two, three or sometimes four hand effort but the general process is.....

  • Generate the steam with a wallpaper steamer directed by hose into an enclosed box with one door and wait until it gets up to 212 degrees.
  • Put the pieces you want to steam bend in for 1 hour for every inch of thickness.
  • When the time is complete, put on some thick leather gloves so you don't scald yourself
  • Open the door, grab one leg, close the door to not let the temperature drop
  • Strap the leg in the correct orientation to the backing metal strap and hold in place with some strategically placed duct tape.
    • I use metal strap to keep the outside face of the bend in compression to avoid the tendency to crack
    • I use duct tape simply as a quick way to adhere the leg to the strap
  • Wedge the end to hold the end snug against the strap
  • Put the top end of the back leg into the form and slowly but smoothly bend it across the form and then wedge it into place across the bend.
  • Repeat for the second leg
  • Clamp everything down
  • Turn off the steam generator
  • Let sit for at least a day - a week is even better.

That's all I was able to get done this weekend as we had other activities Saturday night and Sunday I needed to get at some yard work. But it is incredibly rewarding to get back into a project that I have enjoyed so many times previously. These chairs have some interesting challenges, but if you follow all the methods and lay them out correctly when you cut teh mortises they are forgiving, light and very strong.

What did you create this weekend?