Replies

1. 
   byhammerandhand | Apr 04, 2006 01:38am | #1

   Interesting question. I am currently reading Zachary Taylor's "Wood Bender's Handbook," http://www.amazon.com/gp/product/0806997028/sr=8-1/qid=1144103631/ref=sr_1_1/102-5162940-5550504?%5Fencoding=UTF8

   He does not discuss altitude in the chapter on steaming, but does say, "The purpose of steaming is not to saturate the wood material with steam, but to heat it and the moisture contain within to soften the fibers." (p.59). So you have to wonder if there's something magic about 212 degrees F, that you don't reach with 203 degree F?

   I bend shaker box sides in hot water bath below the boiling point, so I think not.

1. 
   John_D | Apr 04, 2006 10:10am | #2

   One magical thing that happens at 212 (at sea level) is that water begins to turn to steam.  I don't know the process by which the wood becomes bendable, but it does not amaze me to think that liquids turning to gas within the wood itself would have an effect on mechanical integrity.

   Too, I've read that steaming wood is one way to dry it.  The most likely explanation, to a layman such as me, is that when the water within the wood turns to steam, it expands and is forced from the wood.My goal is for my work to outlast me.  Expect my joinery to get simpler as time goes by.

2. 
   AndyE | Apr 05, 2006 01:31am | #3

   I am just guessing but the temperature could be the issue. BUT, since it is not the temperature of the boiling water but the temperature of the steam that will be heating the wood there may be a solution. Steam can be hotter than the boiling point of the water by increasing the pressure of the steam chamber. So I would try building a steambox to see if the temp you reach is hot enough. If not then you could experiment with sealing the seams of the box to increase the pressure and thereby increase the temp in the box.

   BEWARE: by increasing the pressure in the box you could create an explosive situation. Build the box with a pressure guage to keep it at a manageable level and include a check valve to keep the pressure below a preset psi. If using PVC, check the PSI rating stamped on the pipe and keep well away from that. I don't know how the addition of heat will affect that rating. That is an issue for an engineer or the pipe manufacturer.

   Either way, I am curious to see if those few degrees of difference will make it impossible to bend the wood. Good luck.

   Andy

   "It seemed like a good idea at the time"

1. 
   John_D | Apr 05, 2006 10:02am | #4

   The temperature of steam is, by definition, higher than the boiling point of water.  Pressurization is not necessary.  Also by definition, immersion in "boiling" water limits the attainable temperature to that boiling point.

   If the effect of the steam chamber is, as seems logical to me, to turn the water within the wood to steam, you're going to have a hard time attaining that by immersion in even boiling water.  A steam chamber is going to be far more effective.

   We all know, though, that some relatively stiff substances become much more pliable when simply wetted, even at relatively low temperatures.  For example, you may find you can bend a reed around a pencil without breaking, if you first soak it in simply warm (like 110°) water.  This effect may well be distinct from the plasticization that occurs in a steam chamber, I don't know.  So I have no disagreement with the previous poster who said that he gets good results in hot (not boiling) water.My goal is for my work to outlast me.  Expect my joinery to get simpler as time goes by.

1. 
   AndyE | Apr 05, 2006 04:02pm | #5

   John,I had to read through all the posts again, a few times, but finally came to the conclusion that we agree, I think. I was merely trying to give him an idea on how to increase the temerature in the steam chamber (through increased pressure). It read to me that his outside advice suggested that the lower boiling temp of water at his altitude would not get the steam hot enough to allow the wood to soften and bend well."We all know, though, that some relatively stiff substances become much more pliable when simply wetted, even at relatively low temperatures." -The first thing that came to mind was biscotti.Andy"It seemed like a good idea at the time"

1. 
   John_D | Apr 05, 2006 08:46pm | #6

   I see your point, too.  This is really an interesting topic -- I think I'm going to have to do some research and experimentation (though high altitude isn't in the cards!)My goal is for my work to outlast me.  Expect my joinery to get simpler as time goes by.

2. 
   woodsanga | Apr 06, 2006 09:56pm | #7

   Thank you for your response. This is an intriguing direction and will ask around as you suggested. Thanks for the great idea.

   TJ

1. 
   AndyE | Apr 07, 2006 02:08am | #8

   Just poking my nose in... Not that I would ever have the opportunity to do any high altitude bending, but I would like to know if you do run into any trouble. Keep us posted.
   Andy"It seemed like a good idea at the time"

3. 
   Patto | Apr 07, 2006 06:17am | #9

   The only steam box I have ever used was an old steel army trunk which had a rubber gasket around the lid to keep it waterproof, but it might solve this problem.

   All I did was put about an 1" on water in the bottom of the trunk which was resting over my BBQ. I lit a fire under the trunk until I had the water boiling and put in the timber propped up on bricks to keep them in the steam.

   The pressure guage was a brick resting on the lid (which was not locked).

   This setup worked great, only disadvantage is the length of timber that will fit in the trunk.