heat treating/ fire hardening and colour change

[bassman]

Over a  fire I use a leather glove, and heat treat one limb then the other as I go. I string the bow backwards. You can get heat to penetrate from the belly through the back with with very little color change to the belly. The back will feel very hot to the touch. Then I switch to the other limb,and go back ,and forth like that till I get a good heat treat.

[Tom Dulaney]

High temperatures weaken wood and particularly affect modulus of rupture. See kiln dried wood vs air dried.

It is impossible to change the color of wood fibers by heating them, without imparting damage.


The American Indian bowyer Ishi considered it bad and amateurish to discolor arrows when straightening them with heat.


I have never seen evidence of heat treating on any archaelogical bows or arrows from traditional cultures, English longbows, American Indian bows,  central Asian bows, etc.

[PatM]

You need to look harder.

 Ishi also  apparently couldn't reliably tie a knot to keep his bow strung.  That doesn't mean it's not a good idea to learn a new technique.

[Deerhunter21]

 

High temperatures weaken wood and particularly affect modulus of rupture. See kiln dried wood vs air dried.
It is impossible to change the color of wood fibers by heating them, without imparting damage.
The American Indian bowyer Ishi considered it bad and amateurish to discolor arrows when straightening them with heat.
I have never seen evidence of heat treating on any archaelogical bows or arrows from traditional cultures, English longbows, American Indian bows,  central Asian bows, etc.

 

[Selfbowman]

High temperatures weaken wood and particularly affect modulus of rupture. See kiln dried wood vs air dried.

It is impossible to change the color of wood fibers by heating them, without imparting damage.


The American Indian bowyer Ishi considered it bad and amateurish to discolor arrows when straightening them with heat.
I have never seen evidence of heat treating on any archaelogical bows or arrows from traditional cultures, English longbows, American Indian bows,  central Asian bows, etc.

You can build them that way for sure but it’s not the better shooting bow. Just  facts. That being said enjoy your builds. Arvin

[Tom Dulaney]

You need to look harder.

 Ishi also  apparently couldn't reliably tie a knot to keep his bow strung.  That doesn't mean it's not a good idea to learn a new technique.

Ok, but just because Ishi wasn't good at one thing, doesn't mean he was devoid of any knowledge at all.

It's a well documented fact that heat damages wood. Quoting Myer Kutz, Handbook of Environmental Degradation of Materials (2018):

Hemicelluloses are generally most susceptible to heat damage, followed by cellulose and, finally, lignin. Damage can begin to occur as temperatures reach 100⁰c, but the effects are very gradual at these temperatures (Zabel and Morrel, 1992).

The question is, how gradual is the damage imparted by heat treating as applied by people on this forum? If it results in as little as 5% loss of MOR, that is kind of a big deal for a bending object like a bow or an arrow.

[PatM]

That's why people experiment to get the  maximum gains with the minimum risks.

 Just like the guys making tempered bamboo flyrods.

[Tom Dulaney]

I agree Pat, but without documented tests and investigations, it's still hocus pocus.

[PatM]

  Did you look for tests or do any yourself?   What works is real.

[Deerhunter21]

well heres the thing. anything bad that happens during a good heat treat ISNT A BIG DEAL and heres my proof. go to any thread where someone is showing off a heat treated bow. guess what.... that piece of wood is still a bow. And there are some AWESOME heat treated wood bows!


thats the bottom line. heat treating is not going to cause failure if done right, and if done right it can make a bow better. and you can say whatever you want about how it doesnt and how it damages a bow but, facts dont care about what you say. if you say that a heat treated bow will be bad, it doesnt matter because what you say does not determine how good a bow is. what matters is how you make the bow.

maybe wood does get damaged, maybe were heating it to just before it gets damaged to make it harder, maybe we think we know why but we actually dont, maybe we just dont know how it works. but no matter how it works or what happens, heat treating works if done right and in the right scenarios.

[Selfbowman]

Young man I respect Your enthusiasm and ability to read articles in depth. I’ve been building bows as long as you have been drawing a breath of air. That does not make me a person of superior knowledge. I have not built thousands of bows but. Have hundreds. This knowledge you are challenging has been proven to be successful and has been shared by hundreds on this and other forums . It just works and that’s why it’s done. The old archers and bowyers of years gone by did what you and all of the rest us are trying to do. Build a better bow. Again happy bow making. Arvin

[Digital Caveman]

We all know that heat should not be applied the the back of a bow.  This doesn't mean it's not good for the belly.  There is more to it than simply good or bad. 

[meanewood]

I did an experiment with heat treating on two Elm longbows.
I used the best comparison you can get, a large sapling split in half (twins) and seasoned them the same. They were roughed out at the same time, to the same dimensions and were very close to the same mass all along the process.
They were also very straight, so the tillering was very similar.
So one got heat treated at about 20in and again at full draw all sanded up.
The other got no heat treat at all.
Result, both shoot well and have the same draw weight.
The heat treated one took a fraction less set and 'feels' more springy and also outshoots the other by about 4-5m on average.
I didn't heat treat to the extent of changing the colour too much because I don't like that look and I oil the bow during the process to prevent it.
My conclusion is that it does make a better bow performance wise but it may reduce the life span, but I won't know that until one of them fails.

[Marc St Louis]

There were actually documented tests done by an engineer in CA on heat-treating a few years ago, can't remember his name right now.  These tests were performed at a university where he taught/teaches by some of his students who performed these tests under controlled conditions.  He sent me the results of the tests, which I can't seem to find right now either, and there were indeed positive results to heat-treating bow wood.  The person in question is a well known figure in the bow building world, blast his name is on the tip of my tongue.

[Tom Dulaney]

There were actually documented tests done by an engineer in CA on heat-treating a few years ago, can't remember his name right now.  These tests were performed at a university where he taught/teaches by some of his students who performed these tests under controlled conditions.  He sent me the results of the tests, which I can't seem to find right now either, and there were indeed positive results to heat-treating bow wood.  The person in question is a well known figure in the bow building world, blast his name is on the tip of my tongue.

Can't tell you the number of times I've heard something similar to this, only to later find out that there was no such study.