Technical Difficulties from on Top of the Mountain
2004-04-15
  Doing dangerous things in the fire
A couple years ago I was staring throw the glass in the front of my woodstove, and thinking that those wispy blue flames coming up off the coals were probably very hot. This led to a dumb idea--maybe I could melt stuff in there.

My first thought was to melt metal without too much thought to what kind of metal I might melt. My neighbor is a welder for the county, so after mentioning it to him, he brought me some metal shavings from work, which were naturally steel. Now a woodstove is made out of a close relative of steel, namely cast iron. So if that flame inside was going to be hot enough to melt steel, the structural integrity of the woodstove was going to be in serious trouble. Luckily it doesn't get nearly that hot.

How hot does it get? Well, the thermometer on the outside of the side of the stove routinely gets up to 600F, and the thermometer on the flue can easily get to 900F if I run the stove wide open (lots of air, lots of flame straight up the chimney), and the thermometer above the catalytic converter will run 1,000-1,100F pretty regularly. (No, the stove doesn't have any more thermometers, just the three.) So it easily is above 1,000F inside the stove. Could be 1,500F or even 2,000F when I really have it blasting.

So after doing a bunch of reading on the net and taking the night school metal working class, I now know that I could easily melt aluminum in the stove. I might be able to melt copper, and is an outside possibility for melting brass. (Brass melts somewhere around 2,200-2,300F) I also found out that once you've burned the wood to the point that its turned into coals, all the volatiles are gone, and you just have charcoal left which is giving off carbon monoxide (which burns and turns into carbon dioxide). So if I was really motivated, I could go look up the flame temperature for CO/air, and I'd know what my maximum temperature was.

My first task was finding something to melt the metal in (since I didn't want to have it dripping around in the stove). A crucible is the ideal thing, but they normally cost money, and I didn't have the materials and tools sitting around to make my own. On several of the backyard melting sites people were using steel kitchen utensils (pots, ladles, measuring cups) so I was thinking maybe a baking tray of some sort (which would make neat sized ingots if I could melt enough metal. I finally decided on a bread pan.


No I did not get the bread pan from the kitchen, my wife would not be pleased with me melting her bakeware. I picked one up for 49 cents at the salvation army--a great place for items to experiment with.
The problem with aluminum is that it oxidizes really easily, and it also burns really easily. I've basically turned several pieces of tinfoil into ash at this point. I don't have many copper scraps, and the only brass I have is some empty 22 shell casings. So I needed something else to melt.

Last night I was sorting the recycling, plastics and metal cans go into the general pickup bin while junk mail catalogs and glass each have to be separate out and taking down to the main facility bins. We don't really use that much glass, so I hadn't emptied that bin in about three years, but I got to thinking--hey, maybe I can melt the glass.

So once I had a good fire going and burned down to coals, I stuck a few pieces of glass in my bread tin and loaded it up into the fire. First I just let it heat up a bit, then I added some air through the bottom ash grate to get it going hotter. The pan started to show red spots, but the glass wasn't melting. I gave it a little while longer and the pan started glowing enough that it lit up the glass from below--pretty cool, but it still wasn't melting. I took a closer look and I saw that where the glass was sitting on the pan it was darker than the rest ot the metal, so maybe it hadn't warmed up yet. So I kept it going for a few minutes more, peaking in through the window. I was beginning to give up hope, when the rim of one jar started sagging. Yes, it was finally melting. I let it go a little while longer and then pulled the pan out of the fire which is pretty hard to do since I don't have crucible tongs or any other high temperature pliars--basically I have to use the fire poker and ash shovel.

The coolest thing was watching this cool down. The pan itself is pretty thin, like 16 or 18 gauge sheet metal, so it cools down pretty fast. But where the lump of glass was sitting, it wasn't cooling down right away, so very quickly I got this red spot of hot metal, covered and distorted by a lump of glass, surrounded by black. Should have gotten a picture. I took the whole mess outside to let it cool down overnight. We'll check out how it turned out in more detail tomorrow.

 
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Life in the middle of nowhere, remote programming to try and support it, startups, children, and some tinkering when I get a chance.

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Feb '04
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Mar '04
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Apr '04
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Doing dangerous things in the fire.
The Real Way to get a job

May '04
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