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Fire hardening vs heat gun tempering
Pat B:
I think the results would be probably pretty much the same so it would depend on what's the most convenient and effective for you. For me, it's using a heat gun and a caul in my shop. I don't build many fires outside and especially over the fall and winter when our wildfire danger is at the highest levels.
I've use heat treating not only on whitewoods where it's most effective but I have also used it for osage and locust. I usually do this as I'm making corrections and adding reflex. I think it is very effective for locust, at least it is for me. With osage it may or may not be but I do it anyway as I make corrections. I haven't made many yew bows so I don't think I've used heat treating for yew.
Selfbowman:
I haven’t tried the coals only the heat gun . What distance from the coals is the bow . But yes about 300 degrees is what I get with heat gun about 2-3” away from the bow.
superdav95:
--- Quote from: Muskyman on November 21, 2022, 09:22:14 am ---Great topic for me and guys like me. I could ask many questions as follow ups about this. Going to start with one and try not to hijack Kidders thread. Seen lots of people using this on white wood bows. How about Osage and yew wood bows over coals?
--- End quote ---
I have heat corrected and heat treated yew and Osage but not to the same depth or duration as I would for white wood. Heat treatment of wood is a very big topic and this could result in many related tangents. For example… I have also heat treated bamboo bows. Bamboo could be a discussion topic all on its own! I have done some pretty extensive testing and failure limits on bamboo. What I’ve discovered is that there is a sweet spot for bamboo. 170 degrees for about 2-3 hours. 90 mins minimum for a typical limb thickness. More if thicker of course. I’ve gotten away with little higher but it’s risky. Higher then 170 degrees the tension strength falls off. Compression strength also increases also with bamboo but not to the same levels as white woods. I use radiant heat initially to get moisture out slowly to avoid cracking and get a light brown cook on the belly. Then I use convection oven to get the rest of the way for remaining hour or two. I never use heat gun on bamboo. It likes radiant heat better in my experience. I’ve found good results with heat gun on white woods if moisture content is below 10%. Once heat treated right it resists moisture Re absorption compared to before heat treatment. As few yew I have used heat Gun to induce reflex into a bow but not a full blown heat treatment. Hope this helps.
Muskyman:
I have watched a video about cooking white wood bows over charcoal. I tried it once on a bow I had already ruined by trying to tiller it when it was not dry enough. It seemed to help but it was really to late for that stave. I’m going to try again and have built a pit with concrete block and lined the bottom with fire brick. There is a video by Keith Shannon and Thad Beckum about fire hardening white wood bows you can buy online. I don’t have it but might get it. I don’t think I have the patience to do it with a heat gun.
superdav95:
Yes that’s a good bit of info by those guys. There’s a lot of info that is not included in there that you will have to tweak and learn by trial and error. That’s how I did it anyway. I did my first few with charcol brickets like they did. I’ve since moved to hardwood coals which last a little longer and more even heat I find. I used large stones for my pit walls and dug down a bit. I start my large fire in another round pit and use a shovel to transport my hot coals to my long pit. The reading I get on my infrared heat sensor gun is anywhere between 250-350 degrees there abouts. I concentrate my coals more on the working areas of the limbs to get a good cook. I watch for penetration of light brown through the thickness of the limb creeping towards the back. I’m one of the videos that I saw they use their hand as a heat guage to determine how high to set your bow above the coals to cook. The majority of the brown happens in the last hour. The first couple hours is drying slowly and getting the wood ready to deep cook. If you have it too close too soon it will scorch the surface and not penetrate well and likley split of check on ya. As they say, “low and slow”. I get my bow blank to just past floor tiller usually but have done them at brace. I have done a fully shot in bow but don’t get as favourable results. I find it puts strain on the bow trying to harden up stresses and compressed belly by fully shot in bow. The fibers of the belly are stronger k find if not stressed too much prior to heat treatment. Hickory is pretty tough and will still shoot fine but speed is better if you wait. Hope this helps and don’t hesitate to ask questions.
Cheers
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