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This is an excellent article, and shows why you need to do all the fussy finicky things that you need to.

It touches on two stories of personal interest to me. First, my maternal grandfather spent a fair amount of his time in a silver mine in the blacksmith shop. This was a small enough mine that mining was done with picks, shovels and the like. They would wear out, and need to go to the blacksmith shop to be refurbished. We had an old open coal forge that had been used by the previous owner sitting unused in one of our sheds. Grandpa came by one day to fix up one of his pickaxes. The forge had a blower powered by a hand crank. He first scooped the coal out from the hole in the middle of the bottom of the body of the forge. Then took a coffee can, placed it over the hole, and packed coal around the can, and sprayed water on it. He had me turn the crank as he lit the coal, gently at first, then stronger.

Once the heat was up, he began heating the tip of the axe. As he heated, he told stories of how you heat, then cool the tool. Too much heat could burn the tool. And when to take it out to shape the tool on the anvil. And how there was different types of quenching--water, oil. Depending on what the tool was to be used for.

The other story is that my brother (now retired) was a professional welder and instrument maker. He made instruments for telescopes. As a gift, he once gave me a pair of dice made of aluminum. Not particularly fancy, but he noted that the trick with aluminum is that it will suddenly melt on you without turning red.




without turning red.

Metal light emission depends almost entirely on blackbody radiation [0] which depends only on temperature. Aluminum melts at lower temperatures than iron and that's why iron glows before it melts and aluminum doesn't.

Blackbody radiation is also the principal source of sunlight (and all starlight). It was one of the first physical phenomena that required the quantum theory of energy to explain.

[0] http://en.wikipedia.org/wiki/Black-body_radiation


Indeed, though the iron crucible I use gets hot enough to be red hot. Whether the molten aluminum has a faint red glow about it or not I cannot say; I don't usually melt it at night.




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