We're all familiar with the streams of sparks that result from grinding metal, my idea is to use very high speed camera to capture the sparks as individual points of light rather than streaks. The result would be a picture of the worker surrounded by a swarm of light-points like a little galaxy.
-- simonj, Oct 05 2008

Almost http://www.flickr.c..._atkins/1679923524/
Still contains a little motion. [wagster, Oct 06 2008]

Like this? http://www.flickr.c...tos/apol3/93408516/
Pretty galactic... [wagster, Oct 06 2008]

Pretty!

I read long ago that different metals give off different spark shapes, but I haven't been able to confirm that in modern times.
-- baconbrain, Oct 06 2008


I'm pretty certain that there aren't enough welders around to populate a galaxy - even a mini one. Fortunately this idea is better than the title suggests, although I am concerned that it has probably been done many, many times.
-- wagster, Oct 06 2008


There's a problem with this. The very highest-speed high-speed cameras usually use a very short-duration flash. This, for example, is how you get those shots of apples exploding as bullets go through them, and stuff like that.

To "freeze" very fast-moving sparks, you can't use a flash, so you would have to use a high-speed shutter. That's fine (probably doesn't have to be that high-speed, actually), but then you have the problem of getting enough light into the camera.
-- MaxwellBuchanan, Oct 06 2008


[baconbrain], you are right. It is possible to accurately tell the difference between different grades of steel with nothing more than a hand held grinder. Each alloy: Carbon, Molybdenum, Manganese, Silicon, etc. gives a very distinctive spark shape, position and colour. For instance, you probably already know that high carbon steels have sparks that fizz and divide many times. Just from memory, I think manganese makes a spear shape at the end of the spark, although don't test me on that.

I saw a chart of these, about 25 years ago, but since then, I haven't been able to find a good reference (there are plenty of black and white photos!). A steel producer could check the steel grade just prior to shipping it, without taking a sample back to the spectrographic analyser.

The skill is in seeing all those shapes in a fleeting instant, by eye. But now it should be possible to employ a digital camera, and review at leisure.
-- Ling, Oct 06 2008



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