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Fire by Sun
Shadows growing long, clouds passing over the sun. Is it still possible to use a magnifying glass to make fire?
http://www.youtube.com/watch?v=Xjz4Yk93ChE
Earlier in the day I tested it's effectiveness on different tinder types
http://www.youtube.com/watch?v=UnRTlbSs9kA
It wouldn't ignite cotton balls or a single large curly mag shaving, not sure why.
It would ignite quite a few other types of natural and man made tinders as the video shows.
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There are really three issues that you are dealing with. 1. The temperature 2. The reflectivity of the material you are testing and 3. The rate of heat dissipation the material is able to obtain.
The beam of light should generate in the 500°F range +/-. That's enough to burn paper, whose ignition temperature is around 450°F. You can even get ignition of some dry wood. Dry oak is around 480°F.
I would have thought the cotton would have ignited. It's about 90% cellulose and the ignition point is around 450°F. However, it may be reflecting enough of the light to prevent obtaining that high of a temperature.
The magnesium ignites around 600°F and I don't think the magnifying lens will reach that high. At least not a regular lens. A Fresnel lens might. I think a good test would be to put that lens on a thermometer that can register that high. A meat thermometer or candy thermometer should work. It will give you a nice approximation of the temperatures you are achieving at least. I'd try it myself but we are overcast today so there's no sun.
Another nice vid, just the same. And it's a really good subject. The ability to improvise and use what you have available can be a life saver. But so will knowing what will work and what won't so you don't waste time, resources and energy. You've shown some of the things that will and won't work. A little rep you way for it.
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Take a cotton ball and color a big black spot on it with a sharpie. Put some PJ on it and try it again. The white of the cotton reflects heat, the black absorbs it so it should get hotter.
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Could that, Rich. That might just do it!
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Intersting, but the white napkin ignited easily. Also, I compressed the cotton ball flat as I thought the beam may have not been getting concentrated enough.
I would think the beam of light was hotter, but checking it with a thermometer is a thought. Rain all day here or I was going to try a parabolic lens next.
plus, I'm back to school so play times over, forthemostpart.
THanks for the thoughts!
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