Fire hardening vs heat gun tempering

[Kidder]

Is there any difference in effectiveness between the two methods - fire hardening vs heat gun heat treating? Pros and cons of each method?

[bassman211]

You are opening up a can of worms. Some will say heat is heat. Others who have used it may say that it is more effective  in some ways. What I will say in all of this is that since using it to make  bows I see a marked improvement especially with hickory. Next question would be in what ways?  You can go green to finished in a much shorter period of time. Holds reflex, and makes a very snappy bow on par with most of my Osage self bows. Some say it will make hickory more impervious to moisture. That I can't speak to yet . If you have never tried it you owe it to yourself to give it a shot. More complex to set up than taking a heat gun ,and heat treating on a form. JMO. You will get different opinions, so the best thing to do is to try it yourself.

[superdav95]

Kidder.  I personally prefer the hot coal fire pit method as I can do up to 4 bows at a time in a few hours.  I’ve done several also with a heat gun set up if just doing one bow or the wether is horrible.  I’ve found good results with both methods however it’s a little trickier to get a deep cook using a heat gun safely vs a fire pit.  With both make sure mc is below 10% before heat treatment.   A heat gun and get away from you if you don’t pay attention.  For that matter so can the pit.  The major advantage with the radiant heat using the fire pit hot coals method is less checking.  I find that the heat gun with the little blower dries out the wood too quickly and more prone to cracking or checking.  Just my experience with heat gun.  I found that about 3 hours over a hot coal pit with constant monitoring gives better results.  I use my hand to gauge the heat of the pit and raise and lower the bow to get a good cook.  Out side temps have a bearing on how long it may take for the bow to fully cook.  2-3 seconds over the coals before you have to pull hand away is a good temp to get a good slow cook.  Too hot too fast leads to problems.  You want your cook to penetrate almost all the way to the back getting lighter towards the back.  The only real advantage to the heat gun method is that it’s set up is easier and you don’t need a fire pit. It can get a decent cook in less time too.    Like I said good results can be had with both methods.  If your using a caul or form of some kind to put your bow onto make sure to prevent the heat gun blower heat dose t get directed to the back of the bow as it can give bad results.  Make a holder for your heat gun that incorporates a shield of some sort to prevent too much heat getting around the belly onto the back.  This brings up another advantage of the fire pit method.  With the radiant heat cook it less susceptible to this issue.  Hope this helps and let me know if any other details you need. 

Cheers.

[superdav95]

This is just my observations using both methods many times.  I don’t mean to tread on anyones preferred methods or open any cans lol.   

[Muskyman]

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?

[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]

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?

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

[PaSteve]

Really good information Dave.  I like the idea of building a separate fire then transferring the coals. Sounds like a good way to have better control over the fire hardening process.

[organic_archer]

I can only offer my experience, which isn’t to say either method is better than the other. Heat treating with a heat gun takes more hands-on time but gives you more control and less chance of damaging the blank, but also doesn’t do as deep of a treatment.

A bed of coals heats the whole bow all at once and really deeply. I do think it makes them hold more reflex and perform better, but it just dries them out sooo much. In my experience, when it goes well it goes really well, but it doesn’t take much to go too far and end up with firewood. It definitely seemed to exaggerate the chance of failure if the bow had anything more than slight character.

Went through a phase where I made a pile of fire tempered bows. Some really fast shooters were born in those days, but also lost a fair amount of premium wood tinkering with the technique. I’ve since switched back to less intense heat treatments with a heat gun, and less intense drying in a hot box if the blank needs to lose a little leftover moisture.

Edited for more detail.

[superdav95]

I can only offer my experience, which isn’t to say either method is better than the other. Heat treating with a heat gun takes more hands-on time but gives you more control and less chance of damaging the blank, but also doesn’t do as deep of a treatment.

A bed of coals heats the whole bow all at once and really deeply. I do think it makes them hold more reflex and perform better, but it just dries them out sooo much. In my experience, when it goes well it goes really well, but it doesn’t take much to go too far and end up with firewood. It definitely seemed to exaggerate the chance of failure if the bow had anything more than slight character.

Went through a phase where I made a pile of fire tempered bows. Some really fast shooters were born in those days, but also lost a fair amount of premium wood tinkering with the technique. I’ve since switched back to less intense heat treatments with a heat gun, and less intense drying in a hot box if the blank needs to lose a little leftover moisture.

Edited for more detail.

I agree.  I’ve taken a few past the safe point and paid the price.  Some deliberately and some just not being careful enough.  I’ve got some bows that defy logic though and still don’t know how they are still shooting they are so dark.  I would never send them out like that but they still shoot good.   Your also correct that it does dry them out a lot.  I found this to be a good thing though mostly so long as you seal them well and let them acclimate for a few days before finishing the tiller and shooting them.  I’ve jumped the gun before too and rushed it and snapped them as they are so dry and brittle.   As for character staves with a lot of sideways bend or snaky twisting I would use a heat gun for a lighter cook and perform some in shop manipulation to get them little better shape with heat.  I’ve had some that had some nasty propeller twist that I was able to virtually eliminate with heat treatment which is a nice feature.  Sounds like you e had some good results and good shooters with you’re process too. 

Cheers

[Muskyman]

I’ll probably stick with the heat gun for my Osage staves for now and try the coals for white wood staves. I did watch a video Keith Shannon and Thad Beckum did where they took a small diameter hickory tree and cut it down and took it to about floor tiller, then clamped it on a form and cooked it dry over coals and made a bow with it in 12 hours. Shot it through a chronograph at almost 180 feet per second with a 10 grain per pound arrow. Now how long a bow like that might last I have no idea. I don’t plan on trying that but it did get me thinking about how fast I might dry out a hickory stave using heat from coals.

[RyanY]

I think practically there’s little to no difference from a performance standpoint given the mechanism of how it impacts the bow and all of the other variables that can influence performance. Impractically, the guys winning flight shoots are using heat guns as far as I am aware.