Tempering bamboo cores?

[Kopper1013]

What's the purpose of tempering boo? I see on HHA web site they say all their lams on certain bows are individually tempered. Curious what the purpose is? What are they really gaining? And how it's done?

[KenH]

Bamboo is best tempered with a heat gun, toasting the surface to a nice even red-brown and avoiding burning the surface.  

The process helps stiffen the bamboo and give it more strength.  I've built several bamboo selfbows, tempering the flat-sanded inside of the culm, which becomes the back of the bow; there's no purpose served by heat treating the rounded exterior of a culm with its natural skin on.  

Bamboo lams for composite bow building are sanded on both surfaces and, I would think, tempered on the side to be used in compression (towards the belly of the bow)

[Pat B]

I have seen and used caramelized bamboo. It gives it a nice golden brows color for one thing and I believe it also increases compression strength.
Tempered boo is also used in boo back/belly bows for the belly because it increased the compression strength.
I've seen James Parker(huntworthyproductions) scorch bamboo belly strips until they caught fire with a rosebud propane torch. This was on the rind side and it burnt the rind off. He used it instead of horn on the belly of a highly stressed sinew backed Asiatic style horse bow with the tempered boo belly instead of horn. James also makes beautiful boo back and belly longbows, R/D style bows and recurves with heavily tempered boo bellies.

[Mad Max]

cool info, Ken and Pat

[Stagmitis]

Kopper, tempering bamboo completely changes its original character.

Special ovens allow for individual pieces to reach specific internal and external temperatures at various rates of exposure. Too much and the boo becomes brittle, too little and it does not reach its maximum potential. All too often heat treating boo is misunderstood and has very little effect due to the tempering process.

If done correctly, the boo becomes lighter, stiffer, stronger and is not affected by extreme temperature changes. This results in a bow with the highest degree of cast, longevity and hunt ability in diverse conditions.  
The process of properly tempering boo is an art form and is as carefully guarded as building a world class Hill Style bow.  

Had to ask eh?  

[Kopper1013]

Lol thanks guys that answers all my questions and can tell through further search on my own its nothing I'm prepared to dabble in.

[M60gunner]

Tempering also provides for the boo to spring back. One reason boo fly rods use heat treated boo. In real old days the rods had two sets of snake guides. When the rod took a "set" from casting the fisherman switched the line to the other guides.
Not a bow maker but have made rods and could not understand why bowyers do not heat treat as a standard procedure. I know the glass does a lot of the work but wouldn't tempered boo just make it better?

[mikkekeswick]

All the above info is good BUT in a glass bow as a core it makes no difference whatsoever....the core simply keeps the glass the desired distance apart for the draw weight.

[KenH]

Yup -- what Mike said.