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Fire hardening vs heat gun tempering
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:
--- Quote from: Badger on November 23, 2022, 12:37:07 pm --- 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.
--- End quote ---
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
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