Chele

Shamus May I ask why you want car leaf springs? Is it for a project for your self or to make into something to sell? I agree with a few post Why by any questionable /fatigue /old worn out ones? If I just am screwing around for myself ok but to use used metal for a resale puts that object at risk my be of failing where new metal not that costly. I do use train,car truck springs ,chain saws, wire rope and all kinds of good metal but only for myself or art objects. For knives id never use used . It is just the way I do things. My motto is it only cost a tad more to go 1st class so why cut corners on materials ?

Rusty Here are a few others view on gas vs coal. I learned on coal , (ABS 1987),but for what I do ,propane works better as I can control the oxidization of the steel (Damascus)(mokume gane) that I am working on. I can see it better rather than buried in coal or coke plus the heavy toxic metals that coal kicks out and soot everywhere . I hope that this has helped or given you a few more views.

Knifey My be I can expand on your subject and add to the good info I have seen others say to you. You want something like kola wool as a heat insulator and so you do not burn it up or suck into your lungs the nasty wool one adds coats of refractory cement that can handle imho at least 3,000 degrees . I used a mesh wire on top the wool and added (years ago) AP greens refractory cement . I am not sure what is best these days but I'm sure many can fill that part in. Also if your going to use flux buy or make a kiln plate/shelf so the flux does not eat your lining. A few dollars saves you a lot of trouble.