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One of my high school students smelting iron.


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A couple of years ago I offered my Materials Science students extra credit if they wanted to build a bloomery and try to smelt some iron. I showed them a video of one of the times I tried it and there was some initial interest but it soon faded away. Last year I made the same offer and one fellow, Josh, got as far as mixing up DARC dirt from Spanish Red iron oxide glaze. Josh liked the class well enough to take it again this year. It seemed silly for him to just repeat it so I asked him if he wanted to try the smelt again instead of most of the normal classwork.

 

So he built the furnace, broke up the charcoal and last Friday he tried it out behind the high school greenhouse. I got a substitute that day so I could supervise him and I had my classes come out and he explained what he was doing. In MatSci we are studying re/dox reactions so this was a perfect example in action. The other classes just thought it was cool to play with fire.

 

He got a few small chunks of iron but we called it quits after only going through about a quarter of the materials. We had a lot of trouble keeping the tuyeres from clogging with slag. I think the angle on them was too low making the hot zone too high. So instead of the slag pooling below the tuyeres it built up in front of them. We cleaned them over and over but it seemed better to quit and regroup.

 

Even with just a bit of iron he is completely stoked to try it again and I am sure he will. It is great to see him take the initiative on this. I will keep you posted. I only got a couple of pictures.

 

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He started early on a frosty morning.

 

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Having lunch.

 

Here is a blog about the original offer. The Allure of FIre

 

Todd

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I would have loved to have that opportunity in high school. Sadly my teachers quit being teachers at the end of the school day and didnt concern themselves with interesting ways to help us learn. You are definitely doing those students a favor.

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Very cool!!!

 

What a great experiment to run at school!


Looking at the pics. I would suggest that one tuyere would be plenty on a stack that size.
With a bit steeper angle like 20% min.

Baking up the Spanish Red, in some corn meal can help a bunch as well.
If the tuyeres were iron pipe, they were likely melting very fast.

And I learned very early, Don't poke things down into the stack. There is never, a good reason for it.

Way cool!!

 

Mark

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Mark,

Your comment about 1 tuyere vs 2 got me thinking. You need a certain amount (mass or volume) of air at a certain rate to optimal burning. Is it better to have the incoming air concentrated (higher pressure, one small opening)? I would have thought that a lower pressure would be better (less sparks, even burning) as long as the volume/mass is the right amount. I would guess this is discussed somewhere else in this sub-forum, but since it came up here I thought I would ask.

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The only smelter I have ever use more then one tuyere on was a tatara style.
Personally, I think that anything up to a 12in. int. dia. stack smelter needs only one tuyere. Unless your running from separate blowers/bellows, your just splitting your air power, and I'm not sure if that helps anything.
On Darrell's,, and Lee's sites, there are some good air volume/pressure tables. They are a good starting point.
There are always many variables added, and experience seems to be the biggest one.
Having a good tuyere set up is the next biggest factor. You can work with just about anything, but, your tuyere set up can save LOTS of headaches.
With one tuyere, you can get the center of your bloom just about where you want it. Knowing where the bloom will form, helps a bunch.
With a small stack like the one above, you should be able to make iron with one simple bag bellows, so it doesn't take a lot of air.
To me, I would worry about enough burn time, in the reduction zone, with that short a stack. But I have seen the guys in Europe do some fine smelting with very short stacks.
I would think, if you were using unsized Spanish Red, that short fall could be a problem.

Mark

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Tyler-

 

That's a great thing to get the youngsters going.

 

I concur with Mark's comment about poking in the top of the stack, but thought I'd offer a why--


Because the ore is both heavier and smaller than the charcoal, every time you poke or shake the furnace burden the ore will travel faster down than the charcoal. If you do that lots, the cold ore will go directly down there- boom. If he was doing that regularly, it could have even been the predominant reason for you tuyere clogging.

 

In other word- you can poke her in the throat all you want, but she'll never birth a bloom. A well-timed poke from below might be more productive. ...

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Ah Lee. That's hilarious. Neat stuff Todd! Wish more teachers took this kind of interest and maybe more students would reciprocate.

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Thanks for the input. Last week was the end of the semester and with grading and all I haven't had a chance to reply. I think next time I'll recommend one tuyere. The reason we went with two was that with the last smelt I did on my own I had some trouble with a single one clogging up. So I figured that having two would be a backup. Unfortunately the angle was wrong and I think the air didn't burn the charcoal down low enough and so it allowed the slag to build up in front of it.



The reason he was poking it in the frosty picture was that was he had just lit it with kindling. In the later picture he was trying to break through the layer of slag. We were hoping to burn out a lower pocket for the slag. Live and learn.



He is up for trying it again and since he quit early we still have quite a bit of materials. I'll keep you posted.



Todd

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