Fire hardening vs heat gun tempering

[bassman211]

Arvin uses Osage 99 percent of the time if not all the time for flight shooting bows. I am talking hickory white wood. Try the  fire hardening process with that wood. Over all it makes a better bow, and in 3 days from green to finish. That is the can of worms I was talking about.  If I ever make a another hickory bow it will be with that process, and no other. Works best for me. It works well with white oak ,and elm ,but for me to a lesser extent.

[darinputman]

For me fire hardening hickory made a huge difference in finished bow performance. I'm not able to get the same results with a heat gun. I did not get the moisture resistance out of hickory I was hoping for by using the process though. If I had been able to get the moisture resistance I would have a hoard of  hickory staves.
   That being said everyones opinion and abilities vary.  I would love to be able to make a hickory bow, leave in in my shop with my osage bows during humid summers and it not get sluggish,. That is just not the case in my experience. I even used the massey finish on every fire hardend hickory bow I made just to make sure I gave it a fair trial. But they still took on moisture and became sluggish over time in hot humid storage conditions. A couple weeks in the dry box and they came back to life though.
    Firehardening is a great addition to my bow making arsenal and am fairly certain I will be using it in the future.
    One thing I learned from discussions on this subject is that some selfbowyers do not seem to think too highly of the process. I am not one of them I love it.

[superdav95]

Darin.  Results do vary depending on many factors.  I agree that it is a process that works.  I’ve seen the result also myself and know it works.  As for the issue of moisture I’ve also seen this too.  The massy finish is not one I’ve tried yet but will soon one day.  Moisture will always be an issue with hickory more then others in my experience.  This is minimized with a good slow deep heat treatment that is sealed adequately.  It will still loose some speed in humid climates but they do bounce back quicker then non fire hardened bows. That’s the real advantage with the process.  I’ve had yew and Osage loose speed and cast during same humid times of the year.  Bamboo also looses cast depending on the humidity.  It’s wood after all in the end and we can do extreme things to prevent this from happening to some degree but will never eliminate it entirely.  I’ve tried a few hickory bows with a deep heat treatment with both heat gun and coals and immediately saturated the belly with bees wax or pine resin pitch to seal it.  I’ve also experimented with heat activated resins like cactus juice with similar results.  There is a degree of trade off with adding resins and sealers into the pours of the wood.  It adds some weight and therefore reducing cast.  The resins do t penetrate all the way to the center of the bow limb either.  I’ve cut some in half and discovered this so you are left with still having the moisture issues affecting  cast.  One of these day I plan to build a long clear vacuum chamber and saturate a couple bamboo limbs fully then bake them and see the results.  It’s an experiment merely  of curiosity only to prove that moisture can be drastically eliminated with modern resins.  It still will ultimately slow down the bows cast in the end I believe.  I purchased the clear tubing long enough to build my chamber and have the resin so stay tuned for that one.   At the end of the day it’s huge improvement over the raw hickory or other white wood bows from my experience.  It comes down to preference in the end and availability of a pit as to wether guys heat gun or pit harden.  Good results can be had either way.  Both methods require the Boyer to experiment with the process to get it right for his environment.  Up here in Ontario Canada we have a lot of moisture.  That being said all of my white wood bows are heat treated to some degree.  In drier climates elsewhere it may not be as much of a benefit to heat treat.  Great discussion on this and seems like lots of guys out there are doing it with great results.  It’s opened a new world for us that don’t have a good access to Osage which is a good thing.   

[simk]

I love my heatgun for quick corrections and love my quartz radiator for deeper treatments  I wouldn't strongly heatttreat yew or osage because its unneccessary. I would also assume the yew sapwood would snap on any bow after a long and deep heattretating over a fire.
Superdav: On Reply No 7 you mentioned your "convection oven". How does this oven lookalike? Do you have a oven which you can feed whole staves? I'm thinking about building something to heat temper my laminates before glueing them so I'm very interested in oven-ideas.
Cheers

[superdav95]

I love my heatgun for quick corrections and love my quartz radiator for deeper treatments  I wouldn't strongly heatttreat yew or osage because its unneccessary. I would also assume the yew sapwood would snap on any bow after a long and deep heattretating over a fire.
Superdav: On Reply No 7 you mentioned your "convection oven". How does this oven lookalike? Do you have a oven which you can feed whole staves? I'm thinking about building something to heat temper my laminates before glueing them so I'm very interested in oven-ideas.
Cheers

I just use my kitchen oven right now that has a convection feature and it goes to the desired 170 degrees.  The longer section of laminated boo are done with a single element burner in my shop for radiant heat.  I stopped using heat gun on my laminates after splitting so many of them.  I basically only use the convection oven for my short limb pieces for the 5 peice bows.  They just barely fit.  I’ve been thinking of building a convection tube heater that has a shiny stainless steel heat shield for my longer laminated glue ups.  Or just have an array of radiant burners or something but there would be cool spots between the burners.  The best solution to this would be one of those shop tube style radiant heaters.  They come in natural gas or propane powered.  I guess one could build a custom heater using heater coil similar to a kiln or something and make it long enough to suit their needs too.  For me right now the kitchen convection oven works pretty good and is fairly accurate.  For my longer laminated bows I manually run the belly over a single burner to very lightly toast it.  It’s done when I stop seeing steam come out the ends.  I’ve noticed too that I have to re flatten the belly as it develops a rounded convex shape after the heating I’m guessing from expansion when releasing the moisture.  My moisture meter won’t even register a reading below 4-5% and so I’ve resorted to weighing the slats before and after now.  It gives me a better idea as to water loss before glue up.  Hope some of this helps ya. 

Dave

[superdav95]

Here’s a long heater that might work. It’s inferred radiant heat.  No blower.  It’s electric patio style heater that I think might be an option.

[Muskyman]

I was just thinking this morning while walking my dog out back about other ways to put heat to my hickory bow staves. I’ve got a couple of propane heaters that are about 100,000 btu each I use for heating job sites and my shop in the winter. I’d probably have to get a infrared temperature gauge or something to check the temperature at a given distance to know where to hang a stave but they might work, and I can adjust the temperature setting somewhat. I wouldn’t use it for much but it might work to dry out a hickory stave some. I like all the tried and true methods but I’ve said before I’m impatient and I’m willing to try other things to speed up my bow making process. At least with my hickory staves because they are much easier for me to get. They might help get a stave down to around that 10% MC so I can cook them on the coals. Osage might be another story.

[simk]

thanks Superdav, I have that device - it's what I called quartz radiator in my post. Works great but it's only radiant heating from one side. I'm planning to make some kinda oven where I can make full heattreatments under controlled enviroment when I find the time. Basicallly a temper-box that can reach 180 degrees celsius. Basically a well insulated non flammable box. Wondering what temperture one could get using a few 100w lightbulbs in the box and weather the lightbulbs themselves would resist the heat? This would be the easyiest setup but maybe other devices needed to heat the box. cheers

[Badger]

     We have a lot to learn about heat treatment. The one thing I am most curious about is whether would it make a difference if I found an optimum temperature and then held it at that temperature for a specified period of time. For example, 260 degrees for 12 hours.  I have a feeling that we have a virtually unexplored science here and a good place for up-and-coming bow makers to make their mark. I know when they cure fiberglass fishing polls they go through a long process of slowly bringing the temp up and then slowly bringing it down in stages where they will hold it at each stage for a specified amount of time. I have a feeling that bow heat treating would be similar.

[superdav95]

     We have a lot to learn about heat treatment. The one thing I am most curious about is whether would it make a difference if I found an optimum temperature and then held it at that temperature for a specified period of time. For example, 260 degrees for 12 hours.  I have a feeling that we have a virtually unexplored science here and a good place for up-and-coming bow makers to make their mark. I know when they cure fiberglass fishing polls they go through a long process of slowly bringing the temp up and then slowly bringing it down in stages where they will hold it at each stage for a specified amount of time. I have a feeling that bow heat treating would be similar.

That so funny!  Badger I was just reading this article I found this am.  I’ll post a link for those interested.  Now it refers to bamboo testing specifically but some of the theory would apply to other species also I imagine.  What I find interesting with this study is that I was not far off on my own testing. Such as it was.  I will continue to explore this and do more of my own testing to confirm some of this studies claims anyway but it’s an interesting read for those curious on the topic.  The study basically states that 160 degrees for 1.5hours is optimal.  My own crude tests were not far off but I found that 170 for 3 hours was optimal when it came to moe.  Compression and tension both increased more and dropped off at 180 and higher in my tests.  More moisture was extracted from the bamboo but it became too brittle even after letting it set for a day or two. It brings up some interesting discussion on duration of heat like you say.  I’ve played around with the times too but more can be tested in this area I believe.  Anyway interesting stuff. 

Dave

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1130&context=matesp

[bassman211]

Applied properly heat is a great tool for bow making, and I have used it for other applications. Example... I bought a vintage 83 Kramer bass from a guy in church that was stored in a basement, and the neck had a bad warp in it . I loosened the truss rod, built a jig, and heat treated the rock  maple neck with a heat gun,and got the neck to go back to were it needed to be. Set the neck back up to suit me, and ended up making it one of my favorite bass guitars.

[Muskyman]

Just wondering what kind of infrared thermometer you have Dave. I’ve been looking at them online and pricing is all over the place.  Looking at one Milwaukee makes for around $100.00 but there are much cheaper ones around as well//

[superdav95]

Just wondering what kind of infrared thermometer you have Dave. I’ve been looking at them online and pricing is all over the place.  Looking at one Milwaukee makes for around $100.00 but there are much cheaper ones around as well//

Here’s what I got.  Works good for me.  I used it for heat treat on my knives initially but works for bows too! 

https://www.amazon.ca/gp/aw/d/B085S6F85G?psc=1&ref=ppx_pop_mob_b_asin_title

[Muskyman]

I did put a little reflex in my stave today with my heat gun and did a little tillering to it

[Muskyman]

Picture of the tiller