Tempered bamboo

[wood carver 2]

When I temper the bamboo for my belly lams, I scorch it black with the torch. I was thinking of using such a piece for a back lam as well. Do any of you see a problem in this? Do you think it might break under tension?
Dave.

[LittleBen]

I would speculate that it will be weaker. If it will break is debatable, but it's going to be weaker.

Bamboo already has an extremely high tensile modulus so I doubt you'd gain anything but looks.

Might consider trying to simulate the look instead, maybe charcoal in suspension in solvent of some kind applied before the finish.

[Roy from Pa]

Go for it and let us know how it works.... Scorching it shouldn't hurt the integrity of the boo in my opinion..

[Bowjunkie]

I'm leaning the other way. I wouldn't scorch anything on the bow's back.

[wood carver 2]

Thanks guys. I'm still thinking about it. I only really want the look. I haven't been able to get the back to look the same as the belly and I want an all dark bow without resorting to paint.
I like the way it goes from black through shades of brown until you get to the untouched boo underneath the scorching when it's sanded.
Maybe, if I only toast it a bit, it might take stain better.
Dave.

[Pat B]

I think that scorching would make the boo less strong in tension.

[Bowjunkie]

Aniline dye will make it as dark as you want it.

[J.F. Miller]

heat/flame tempered bamboo becomes to brittle to be reliable for tension work. is ill advised to temper bamboo for backing. I use aniline dye, too.

[KenH]

Don't "scorch" the boo black!  Use a gentler heat to "toast' it golden brown.  If you burn through the skin of the outside of the culm, or otherwise blacken and char things it will weaken the bamboo, for some value of 'weaken'.

[milehi101]

I built bamboo fly rods for years and it does strengthen the bamboo to heat treat it.  Back in the 1930 they would heat the bamboo at around 325 degrees for a couple of hours.  You can tell those rods because they are almost chocolate brown.  In later years they learned that a lower heat of about 125-150 degrees for 10-12 hours would do the same thing to the bamboo except it would keep it's natural color.  In bamboo their is power fibers that are straight when harvested and dried.  at the above temperatures the fibers tend to curl and lots of them around each other making the bamboo stiffer
and the rod would cast further and faster and even need heavier lines to get them to flex.  When I started making bows Bingham used to sell a natural bamboo of a heat treated bamboo.  I used both and the heat treated had been heated with the higher temperature as they were a darker brown.  I still have a long bow I built from it and it is my favorite bow.

[M60gunner]

X2 what milehi101 says. Heat tempering is what gives the rod its ability to spring back. Flaming as stated does not need to be "black". Also, when flaming boo for a Rod I was taught to flame the whole clum not strips. Proper heat tempering should be done in an "oven" according to some experts.
You could ruin those thin lams using a tourch. If the bow is glassed the glass will do all the work anyway so use a dye.

[wood carver 2]

Thanks for those numbers. It helps to know how much heat to use and for how long. I heat it with a propane torch moving the flame quickly, but I do like the bamboo dark. I'm careful to not burn past the waxy outer coating.
I used to use a butane torch that had a wider and cooler flame, but it leaks now so I'm stuck with the propane. If I overdo the heating, I know right away when I bend the lams up the belly ramps of the riser. They will break.
I discovered a side benefit to flame heating the lams. The bamboo will cup backwards towards the outside edge. This allows me to plane it even flatter and thinner than I could otherwise.
Coming back to those numbers for tempering the boo, this gives me an idea. I could build a solar oven, long and narrow which could bake bamboo lams gently. Heat would be easy to control and it's free to operate.
Dave.

[milehi101]

I do not think a torch is the way to do anything except put a burn design on the Bamboo.  We used 2 6 inch stove pipes with a heater in one and a T fitting to the 2nd pipe.  Their was a heater in the 1 st pipe and a exhaust fan in each end of the 2nd pipe to draw the heat through the 2nd pipe.  I used Dryer thermostats to cycle the temperature in the
2nd pipe this kept the temperature the same and never burned or discolored the bamboo.  Flaming the bamboo woes not give the properties of the bamboo time to do what they do.

[Onehair]

I tried it ONCE.

[Pat B]

I've watched James Parker(huntworthyproductions) temper boo. He uses a rosebud propane torch and really chars the boo. Quite scary to watch. He only used the scorched stuff for bellies.

[wcdurand]

I Agree with milehi. As I build bamboo rods as well, the concept of heat treating bamboo with torch is something that I use often. It is also a well accepted procedure in the cane rod building fraternity. If you want to know more about the principles, google the cane rod sites. It is believed to (and tested) to add stiffness and add to the tension and action of the bamboo. Of course it adds to the aesthetics of the rods as well. The heat treating of the bamboo is a science on its's own. The strenght of bamboo rods is well known and remember that they flex all the time for days at end!