How to limit light thru magnifying glass

I'll try to make this short and to the point - Does anyone know a way (or could think of a way) to make a device that would fit onto a magnifying glass or similar, so when the magnifying glass is used to burn wood/start fires, the burn mark is not as thick? Thanks.

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Bran (author) 10 years ago
Thank you everyone who has answered, next sunny day that comes up I will try out the methods I can that y'all have posted. Thank you!
Kiteman10 years ago
OK, this needs an instructable - some device that focuses a magnifying lens into a light-pipe, allowing the light to be used more conveniently for pyrography or solar soldering, like the bendy extension of a rotary tool.
CameronSS Kiteman10 years ago
Fiber optics?
Kiteman CameronSS10 years ago
Fibre optics don't carry heat, just light (that's why they're used for cold lighting. A light-pipe is a hollow tube with a reflective inner surface - acts just like an optical fibre, but it will carry heat as well.
VIRON Kiteman10 years ago
Fiber optics are most often used to carry infrared light, which is associated with heat. My electric stove lights up on my IR night vision camera for example. Since magnifying glasses do not get hot while in use for burning, nor do they have a pipe like structure to hold hot air in, it doesn't matter if fiber doesn't "carry heat". I do think it's possible that if you focused a magnifying glass on a fiber optic cable end, it might get hot carrying so much light, especially IR, just like a wire gets hot if it carries too much current. And if the fiber remains cold, and if most of the light that goes in comes out the other side, it should burn things as well as the magnifying glass, as if the light went thru the air instead of the fiber or lightpipe. Where is fiber used for "cold lighting"? I suppose if the light source is an incandescent bulb, I agree that the heat from hot air around the bulb doesn't go through the fiber.
Kiteman VIRON10 years ago
"Cold" lighting is used when surgereons need a bright light to see a small area in detail. Rather than illuminate the area with close, hot bulbs (the heat damages delicate tissues), they use fibre optics to guide the light in from a distance.
CameronSS Kiteman10 years ago
Oh, sorry---I misread your post. I thought you just wanted light.
jtobako10 years ago
Try a second, smaller magnifying glass to focus the light from the first. It could be set up in a tube, or just use both hands : )
SacTownSue10 years ago
Years ago I was at a couple of street fair / art faires in the SF south bay area, there was a guy who created "drawings" on wood using a magnifying glass. Seems like he had more than one depending on how soft or deep he wanted to burn the image. It would start smoking, he would pull the lens away, wipe it, burn some more. Solar wood burning. Regular old high quality magnifying glass as has already been mentioned here.
lemonie10 years ago
Good focus. Good alignment. The lens wants to be aligned directly with the sun. One thing you can to is to cast a shadow with e.g. a carboard tube, and adjust the tube until you have a perfect ring of shadow: the tube is aligned correctly with the sun. If you can mount both the lens and tube on a tripod, it's much easier (I should have photographed that, maybe some other sunny day...) L
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