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Cane Prep - Testing

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I just finished straightening and node pressing on 24 new bamboo strips and I think I may have a problem?  All of the strips after soaking exhibited a soft spot where if I bend the strip it will stay bent, no resiliency.  This is not at a node but in a 3 inch section between nodes.  This morning I took one strip and heat dried it for 3 hours and while less of a plastic noodle, the plastic/soft spot remains.  There is no apparent reason for this, the bamboo at this spot looks the same.  Has anyone else experienced this problem?  All 24 strips exhibit this same  problem at the same location.  (Bob McElvain)

Sounds like you got a bad culm -- better keep that one for a nodeless experiment.  (Larry Puckett)

Yes, indeed.  This happens a great deal more frequently than most guys suspect.  For some unknown reason, certain culms (though very few) will exhibit this "softness" between nodes, but when it exists, it is usually in only one such internodal area.  The rest of the culm, up and down its length, probably will be just fine.  Most annoying is that,  outwardly, there will be no telltale signs on the culm to raise your suspicions. Unfortunately, even some of your very best-looking cane may have this problem.

Most builders I know do not bother to check their strips to discover if there is a soft spot, though there is certainly an easy test.  Select any one of your split-out strips from a given culm and, before soaking, simply give EACH internodal area in the strip a good bend between your hands -- feeling for the desired resistance.  Then release to see if the cane snaps back (or nearly back) to its original shape, and move to the next internodal area.  You only need test one strip in this manner, because what pertains to one strip, pertains to the entire culm, and any internodal weakness found in one strip will be present in the same relative position in all the other strips as well.

The bend-test is a "relative" sort of thing (like the "heft" of a good culm), but you will very quickly gain a sense for the feel of really good cane.  A soft internodal area will be very soft in comparison to its neighbors.  Only if you build nodeless, will you be able to salvage the culm -- in which case, obviously, you would simply cut out the bad area along with the nodes.  (Bill Harms)

Yesterday while doing the bend test on strips, a weak spot was noticed about one third of the way from the butt on the butt strip.  Checking the rest of them, I found about 2/3 of them failed at that same point.  Upon releasing the tension, they stayed slightly bent and had no spring.  These strips had been flamed on the outside.  I've flamed some rods,  but never  had any trouble before.  I found enough to make a butt section. 

Seems like the culm may have been bent too much at a young age and ruined only one side that may have collapsed.  Anyone else found similar culms and what was the outcome?  (Tom Ball)

This is not a common problem, but it happens often enough that one should never begin to begin a rod without testing at least one strip taken from your culm.  Sometimes a localized weakness can be caused by careless straightening before shipment, but just as often the problem is a natural "soft spot."  I don't suppose anyone knows why this should occur in an otherwise strong culm, but sometimes it does.  Unfortunately, you cannot rely only upon a visual examination to detect such weak spots.

Flex a test strip by bending it carefully and firmly between each node.  If the strip is of uniform width, each bent section should show a smooth curve with no segment of the curve bending more than another.  When the  pressure is released, the strip should snap smartly back to nearly straight again. If there is a weak spot, you can both feel and see it immediately.

Cane is funny stuff, and sometimes quite unpredictable in its flexing characteristics.  (Bill Harms)

I split a culm that I had been keeping for a larger rod this bamboo had dense power fibers and was heavy with nice color after splitting I began the straightening process and noticed that the cane straightened very easily and with very little heat.  I then tried bending it in every direction without heat and it bent and stayed that way.   It did this in between nodes in several places.  This is my first experience with this (I have been making rods for 5 years) I can’t remember hearing or reading about this anywhere.  The bamboo had no marks or anything that would indicate that it was bad but I ended up throwing it out. I store my bamboo where it is dry and temperature is constant.  I am wondering what would be the cause or is this just a natural occurance has anyone else has had this happen and how common it might be.  (Rick Barbato)

I've only had that happen with one culm and then only for about 3' of it.  It was like a dishrag.  I've had other culms where for about 6", it could be bent anywhere. I'd wondered if the culm had been subjected to too much heat during the straightening process in China.  The 6" ones are usually slightly darker in color that the surrounding cane.  (Don Anderson)

Just a thought...before you actually throw the culm out, why not try to heat treat a few pieces to see if that changes anything.  It would be interesting to see if the heat treating changes the softness. (Mike Biondo)

You should have tried heat treating it first before tossing it.  Then, if it still bent and took a set easily, it's time to toss.  (Mark Wendt)

I had a rod tip would bend just casting it, I had only flamed the bamboo before building the rod so I took the tip section, wrapped guides and all and put it in my oven and cooked at 325 for 8 minutes and no more soft tip. I used epoxy to glue up my rod so it could take the heat. Other glues might not work as well.  (Ken Paterson)