Make:

I remember making these with my father twenty some years ago, rip apart a dead carbon zinc battery, put the rod in the pencil sharpener to give it a nice tip. we used automotive jumper cables to hold the rod and some nails in a board to position them. no ballast resistor was used, just hook the cables straight to a car battery and BAM let there be light! I do recall it was incredibly bright and filled the basement with smoke.

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If you try making one of these then it should be pretty obvious, but worth stating - Don't stare at the arc, it's not going to be good for your retina.

Not that you can really stare at it anyway, since arc lights get very intense and your blink reflex kicks in, but worth reiterating.

Also, there's likely to be a rehash of the old 'Swan/Edison invented the incandescent lamp first' argument, but I'll leave that one well alone :)

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I see how the basic set up works, but how does the wire fit into this, and where does it attach? What's it for? I don't understand.

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When I was in high school, I was the projectionist at an older theater that still used dual arc-light projectors. After switching over for each 20 minute reel of the film, we had to check, and replace if necessary, the carbon rods inside the projector. There were motorized feeders that fed the rods together and the rods were clamped in water-cooled copper holders. There were also knobs outside the projector to adjust the position of the rods. After changing the rods, you would turn on the power and "strike" the rods together to start the light (you watched the arc through a welder's glass tinted window). A large front surface parabolic mirror focused the light through the film.

The projectors were extremely hot, so in the summer the temperature in the projection booth could be very high even with air conditioning. If the air conditioning went out, it would be well over 100 degrees.

If you opened the projector shell without letting it cool down a bit, the big expensive mirrors would crack (happened to another projectionist). If you let the carbon rods burn down too short, they would melt the copper holders and the water from the water cooling rig would spray out and cause all kinds of problems (including shattering the mirror). Never saw that happen, but I heard out it.

BTW, many (if not all) big spotlights still use arc lamps.

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There is a good illustration of a mechanical sounding arc lamp striking in the opening credits of the old TV programme called Connections with James Burke. It is available on YouTube and well worth watching. I think curious Makers would find it interesting.

http://www.youtube.com/watch?v=OcSxL8GUn-g

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