Has any one out there done any experiments using steam to straighten the cane and flatten the nodes?
Have tried a little steam flattening on the nodes (Basically me squashing a few nodes with a steam iron) and the results were worth this post. (Luke Bannister)
Like you, I used an iron, to straighten my splines before final planing. However, I put the splines in the groove of the forms first. They came out remarkably straight. I should do that more i guess. (Geert Poorteman)
Tim Abbott has done quite a bit of steaming and straightening nodes. He did a super nice demo on his procedure at the Corbett Lake Gathering in 2004. The same information may have been in a past issue of The Planing Form, but I don't remember for sure. (Harry Boyd)
At Corbett Lake a couple of years ago, Tim Abbot demonstrated a steam box powered by an electric teapot from Lee Valley. The box is designed to hold 6 strips in individual slots so it will steam the node and a couple of inches on each side of the node. The problem with steam is the time that it takes to heat up a node. With a heat gun you can heat one node in a minute or so while the previous node is cooling in the vice or press. With steam it takes 5 minutes or more to heat up a node sufficiently for straightening. Tim's steam box solves this problem by allowing you to cycle through the nodes of an entire set of strips with five nodes heating up while one is cooling. (Robert Kope)
Soaking, then using a heat gun does the same thing as steaming, but much faster, more concentrated, and thus more efficiently.
Straightening nodes doesn't mean squashing or pressing them; it means heating and straightening the bends, then allowing them to cool while being held against a flat surface. (Ron Grantham)
I'm working on the idea that steam under pressure can be hotter than just steam rising off boiling water (think pressure cooker).
The next step is to stick the digital thermometer probe from my cane oven, under the iron and see what temp I get, hopefully without destroying the the probe
I'm not a fan of soaking although I can give no good reason against it Just personal taste I guess
SO far I've found that after about 1 minute of steam and pressing, I could press/squash the node by about 10 thousandths (pith to outer skin) and it hasn't sprung out .......yet
About 30/45 seconds was enough to allow the cane to be bent straight (?). (Luke Bannister)
I've done a lot of steam bending of wood and I'd think bamboo would be a whole lot easier.
With wood you don't want pressure. It's dangerous and isn't what's needed anyhow. What you do want is wet steam, the wetter the better and lots of it. I don't think steam under pressure is all that wet but it is unsafe to use. (Tony Young)
Steam under the iron is not under pressure. The whole reason for using steam is that it transfers heat more efficiently than dry air. When water boils at 1 atmosphere of pressure, it stays at 212 degrees F regardless of how much heat you apply. The energy supplied as heat is used to convert water to steam by vaporization. If you continue to heat the steam, it will get hotter whether or not it is under pressure. In a pressure cooker, the water is heated above 212 degrees because the vapor pressure of the steam is increased. When the steam condenses on bamboo, it gives up this heat of vaporization, but it gives up this heat at 212 degrees. Dry air is much less efficient at transferring heat, but we can more than compensate by simply making the air hotter. I typically use at least 800 degrees for soaked strips.
The reason that your steam iron heats up the strips faster is that you are directly conducting heat to the bamboo through contact with the metal of the iron, not because the steam is under pressure. (Robert Kope)
My thinking was;
The steam from the iron condenses very quickly dampening the cane, the heat of the iron should boil off the moisture, which is trapped between cane and iron creating a very small increase in pressure. The boiling point of water increasing with pressure (put a few drops of water on a flat surface and put a hot iron on top, definitely does something!).
I'm not thinking 5’ pressure cookers ...........yet. (Luke Bannister)
About 3 or 4 years ago, I did some experimenting with steam. I made an aluminum box about 4 inches long by about 1 1/2 inches square. I made a 1/2 inch hole in each end and the inside of the box was bored out to make a chamber. a copper tube connected the box to a pressure cooker; made an adapter to replace the pressure control that included a pressure gauge. The pressure cooker was placed on the kitchen stove and the temperature adjusted to keep the pressure about 20 PSI. The cane strip was inserted through the holes and the desired node centered in the chamber. a couple of minutes and the node was steamed; temperature around 200F and saturated with water from the steam. It worked but not as well as I liked. I haven't tried it since but I have been thinking about it lately and will try again when I have time. This time I plan to make a flat coil of 1/8" copper tubing and sit the pressure vessel on this and the whole mess on a hot plate. The added heat to the copper tubing will then superheat the steam. Next best thing to a pipe bomb but if I monitor the pressure and keep it low, it should be safe enough. Not sure what the needed temperature for treating the cane is but I believe it is a good bit above 212F to compete with a heat gun. (Onis Cogburn)
I would be interested in seeing more on your experiences with the steam iron. I have read posts in the past regarding the use of an iron to straighten strips but not to press nodes. I would be interested in the your results. Are you soaking your strips prior to straightening, etc. (Wayne Kifer)
After about 30 seconds of steam (and the iron did produce a lot of steam). The strip could be easily be bent straight.
Same on the nodes.
It took bit longer to compress / flatten the node, to get it soft enough to compress it by 15 thousandths took about 45 seconds of steaming.
The process seems OK and I will probably try it on my next rod, which may be a while, got four on the go at the minute which is enough for me.
I liked the fact the with the iron length ways on the strip you could quickly soften a reasonably length of strip and take out those long curves that make planing awkward. (Luke Bannister)