To all wood benders,
We are attempting to steam bend in Denver, Colorado at 5820 feet above sea level. The boiling point of H2O here is 201.7 degrees and normally wood is recommended to be steamed at 212 (sea level) for 1 hour per inch. I constructed a steam box and was able to obtain a temp. of 208.5 max. Question of course is, if the water is at boiling point even though it is below the recommended temp. will the lignum still plastize? And if not, will longer exposure to steam help or hinder process? I know form my experience at sea level that long steaming times can have ill effects. Is there a chart or rule of thumb to follow for thickness, temp and time? I’ve talked to two experts I trust on this who have both told me either I can’t steam here or I can. Please help, I love steam bending and really want to do it here.
t.j.
Replies
Why can't you just make a test run. Take notes along the way and develop your own adjustment factors from that?
TJ,
Really, I don't think a 3.5 degree difference is going to make any difference. Each piece of wood will react differently accordinf to it's specie, size, moisture content, etc., but that small a difference in temperature shouldn't cause any problems. You're kinda high there, but some of my best work is done when I'm high. Give it a try and see. Let us know.
Steve
There are two secrets to keeping one's wife happy.
1. Let her think she's having her own way.
2. Let her have her own way. President Lyndon Baines Johnson
TJ
Don't know all the science variables involved with the boiling point having any bearing on steam bending but I can chime in on 2 points:
I had a friend fly in 8 foot logs of oak from Arkansas to Kirtland AFB, NM. Albuquerque was a little lower than Denver but it was quite a bit drier as I recall. Regardless, the message I have for you is-- if you steam straight grained oak in Colorado it will bend just fine. I never had a failure due to temperature variation. My problem out West was finding good quality straight grained wood that WAS NOT CUT -- IT WAS RIVEN. That is the secret to success not 207 vs 212F.
2 Tips:
1. Don't use dry wood
2 Don't use cut wood and you will be happy. Ignore these rules and you will learn the hard way.
Photo; only the chair seat is cut wood. All the rest is from a log and split with a maul and froe.
Good Luck
tj, I think you should be OK at 208º as long as you don't let it go any lower. I have had some success at that º in cold weather here in LR AR,
Here are some things I would suggest. If you have a good enough closed system chamber that you are sure will not explode by adding a little pressure, and by little, I am thinking 2~3 psi, which is close to the actual pressure drop at that altitude. Let me be the first to tell you that this gets dangerous, but it can be done.
If your chamber is not insulated, this would be a good thing to do. I use a plastic pipe for most things. I rolled it up in about 5 or 6 wraps of 1/8" packing foam. That helped bring my chamber up by about 5º more in cold weather.
As for your question about time. This is relative to a lot of things, but the goal is to get it to around 210 all of the way to the middle. I have been thinking about getting one of those thermometers that you insert into the middle of the hunk of meat, with a cable that runs out to the stove-top. If you drill a hole in the end of one of your blanks, to insert the tip into, this would tell you what you need to know. Although I still would want one measuring the atmosphere inside the chamber also.
Since we are getting into the cold season, working fast after we take the part out of the chamber is important, and having one mishap, can ruin a part. I have been giving some thought to trying something that could insulate the part from heat-loss until the bend is complete. The easiest thing which comes to mind is foil. If you have a length of foil laying out right as the part comes out, then quickly rolling it up in foil might give you a couple of minutes of working time before the lignin starts to set. Even a plastic cling wrap would probably help by eliminating evaporation.
Aside from this, be sure to use the end-compression straps.
tj,
I live up the road in Boulder, and have successfully steam bent walnut. So, I don't think the altitude or small temp differences are a problem. I agree with another poster that it is important to avoid dried wood and try to use straight grained wood with no grain runout. The obvious way to get this is to use riven wood, but I muddled through with cut wood by watching the grain direction carefully when cutting pieces to be bent. Another helpful is to use a bending strap. Lee Valley has them in their online catalog. They put the outside fibers in compression which helps avoid splitting.
Good luck, Tom.
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