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So my question is, if I were to heat a piece of steel to a glowing yellow and then stick it in kaowool so that the whole piece is covered, would that slow down the cooling enough for the steel to be properly annealed?

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What alloy? D2, A2?  Nope never for those alloys! 

How large a piece of steel? Knife blade thicknesses usually need a thicker "helper" to slow the cooling down.

What's the ambient temperature in your shop? -20, +20  C, F or K?

How thick of kaowool?

So far this question is much like: "I have a container of water, if I pour it into this glass will it overflow?"  Can you see how difficult answering such a question can be without all the details?

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The problem would be with the fibers you knock loose from the kaowool becoming airborne. There's so many other things to use it's not worth it. I use wood ash now that I have collected enough but I've also used unscented kitty litter to good effect and plain old dried and pulverized clay I dug out of the ground. Find a metal ammo can or old toolbox and start saving wood ash in it or buy a bag of vermiculite at the garden center. It's that time of year when the box stores are preparing for spring in my neck of the woods so it's already stacked up outside of Walmart. 

Pnut

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The short answer is Yes, it will work for any steel that you would otherwise anneal by burying it in ash, lime, vermiculite, and so on (although as noted above, yellow is hotter than necessary). One of my smithing mentors does this all the time, often adding an appropriately sized bar of mild steel heated to the same temperature as workpiece to slow down the cooling rate even more.

The safety issue is non-trivial, but we do have to keep in mind that there is a BIG difference between (a) loose fibers becoming airborne after being subjected to the heat of the forge and blasted out into the air by a gas burner and (b) loose fibers that happen to detach from a kaowool blanket at room temperature. The former behave a lot more like asbestos and pose a much higher risk than the latter.

I know that others here may disagree with me on this, but I think that we sometimes overstate the risks of kaowool and ascribe the worst-case effects to ALL possible situations. While plain kaowool fibers can cause silicosis or even cancer with repeated long-term exposure, they are not toxic and not nearly as dangerous as asbestos. Outside the extreme environment of a gas forge and with appropriate precautions (dust mask, etc), I personally don't consider this usage to be significantly unsafe.

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you are forgetting its not just operating temps, in his annealing scenario he is also stirring up the fibers, that does not happen in a forge, so I fear you have a very different idea of what is unsafe than most of us

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Steve, how do you mean "stirring up the fibers"? I don't think he's talking about sticking a piece into a bin full of shredded kaowool, but putting it between two layers of blanket. The first would certainly be dangerous, as both the shredding and the sticking would release fibers into the air, but the second wouldn't -- or at least, not nearly as much. 

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While I agree with John that this isn't the use case for ceramic blanket that poses the most risk, it's kind of a moot point given the numerous other (much safer) options that are available for annealing that have already been given above. Like many risks, it's a roll of the dice whether or not one has adverse reactions to some degree or another. And the probability goes up with the amount of exposure you get. I guess the question is why roll those particular dice at all if you don't have to. Even if the odds everything will be fine are arguably in your favor.

Using ceramic blanket would work, but it seems like more of a hassle to me to put on my respirator and be all careful when I could just as easily bury the steel in a bucket of vermiculite and call it a day. Just my 2 cents.

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So the thought came from hearing about how glassworkers would sit their work in fiberglass insulation or something like that to slow down the cooling process to prevent the work from cracking from uneven cooling. I don't know how true this is but that's how I had the idea to use kaowool. I think I'll just make a wood ash and lime powder bend to anneal my work pieces in. 

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Good Morning W.Nomad,

Thomas Powers asked you a question yesterday, I haven't seen a reply. "What material are you working with? D2, A2, W1, H13, S7, LMNOP? They all have very different Heat Treating characteristics. It is not a case of guessing and hoping you have it right. To Care for what you are building, YOU have to care enough to KNOW what you are working with. Junk Yard Dog material doesn't set a consistent base-line. You are concerned about Annealling, Why?? Different material Anneals at different procedures. Does it need to be annealed or are you just rowing the boat? Row, Row, Row the boat, gently down.........LOL

Neil

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