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Burning Glass

Discussion in 'Bushcraft' started by Hispeedal2, Jun 5, 2011.

  1. Hispeedal2

    Hispeedal2 Nay Sayer

    I was goofing on Ebay and found these:
    2" Magnifying/Firestarting Glass - Mountain Man/Camping | eBay

    Out of curiosity, I started doing some quick online research to see if it a magnifying glass would be period correct. It turns out the darn things have been used for like 2,000 years:
    Burning glass - Wikipedia, the free encyclopedia

    I thought it was interesting and figured I would pass it along. It will please the boy in ya' like it did me...burning ants................................................. [reddevil]
    Bear likes this.
  2. -06

    -06 Monkey+++

    Keep about a 4 inch lens in the BOB wrapped in an old sock. It is chipped and worn but will start a fire in quick order.
  3. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    For those of us that wear glasses, some grinds might work. (Mine does in BRIGHT sun.) Well worth an experiment.
  4. JBillh

    JBillh Monkey+

    Hi Folks,

    Anyone know if you can use artificial light or any other radiation or energy source to start a fire with a magnifying glass?


  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Any Photon source will work, IF it has the Power Density input to get the required output heat to push the tinder up past Ignition Temps.....
  6. wags_01

    wags_01 Monkey+

    I carry a cheap 2"x5" fresnel lens in my BOB. It's waaaayyyy lighter than an equally sized glass, will never break, plus I picked it up for free with a book purchase.
  7. Hispeedal2

    Hispeedal2 Nay Sayer

    Do plastic lenses have any problems melting when used consistently in this capacity?

    I mean plastic is great because it won't break and it's light, but glass will never lose shape or flat out melt.

    Any experiences there?
  8. Seacowboys

    Seacowboys Senior Member Founding Member

    Many moons ago in a land far away, a friend of mine paddled out to an empty Cay and spent three or four weeks with just his magnifying glass, some LSD, and a large plank of mahogany that washed ashore. When he finally got located, the plank had the most amazing wood burning of a general store, complete with shelves of products with such detail that you could read the labels on soup cans.
    tacmotusn and Brokor like this.
  9. BTPost

    BTPost Old Fart Snow Monkey Moderator

    I have a 6" diameter Magnifying Glass, that came out of an old Analog Marine Radar Viewing Hood, for my Burning Glass. Works really well. I also have one of those Circle Lamps with the Magnifier in the center for precision Electronics work, that does a nice job as well. You can't beat the Magnets, recovered from old Marine Radar Magnetron tubes, for strong Magnets. ..... YMMV...
  10. BAT1

    BAT1 Cowboys know no fear

    I have a magnifying glass in every one of my bags. Guaranteed to last as long as the Sun.
  11. vegasrandall

    vegasrandall Monkey+++

    Old projection tv's have a big fresnel lens in them.metal melting temps can be achieved.
  12. chelloveck

    chelloveck Diabolus Causidicus

    Plastic, Ice and Condoms

    Plastic, ice, and water filled condom lenses when properly shaped will work effectively as fire starting lenses.

    The light being refracted through the lense will not cause the refracting medium or the lense to heat up ( at least not to the point of melting), it is the concentration of the light energy at the focal point that will heat up combustible materials to ignition point.

    If using an ice lense, radiated and conducted heat from your hands will melt the lense, so insulate the point of contact with insulation by wearing gloves.

    Caveats to the use of water lenses made with condoms are:- that shaping the lense to the optimal shape (spheroid) will require some experiment and manual manipulation (trying to keep a straight face here). The use of ribbed, textured or coloured condoms may have sub optimal results. I don't think there would be any advantage or disadvantage to using lubricated condoms as opposed to unlubricated condoms. Flavoured condoms will probably not affect light refraction, but may make water stored in condoms taste slightly more palatable.

    Plastic lenses are quite satisfactory as fire starters, they may be susceptible to scratching which may affect performance. YMMV
    dragonfly and Hispeedal2 like this.
  13. Hispeedal2

    Hispeedal2 Nay Sayer

    That makes sense now. Thanks for explaining. Plastic scratching is something that I am well aware of. It's common, in the Army, to carry a signal mirror as a part of your kit. This doubles as a shaving mirror. Leaving for a one month exercise, one time, I couldn't find my signal mirror. I ran to the PX and found one of the Starflash mirrors. It rode in my ruck for a couple weeks before I couldn't even see to shave my face in it anymore. After that, I bought several glass mirrors so I have a couple spares.

    I think I am going to look around for a few of those 2" glass lenses to drop in my kit and I'll give one to my oldest daughter for fun.
  14. lnfidel

    lnfidel Monkey+

    ~≈ B S Å ≈~

    This topic takes me back to the old scouting days. Now I gotta dig out the shoebox. (like I still have it!) Next stop will be the dollar store to see if they have any. It's good thing to have in case I lose my glasses anyway. :|
  15. dragonfly

    dragonfly Monkey+++

    Just a couple weeks ago the local ACE hardware store here had the 2 inch glass magnifying lenses, with metal frames and handles, for only $1 each!
    I'll have to go and see if they still have some...they had a box full of maybe 24 or so. I bought 2 for the heck of it.
  16. Tikka

    Tikka Monkey+++

    On TV I've seen broken glass work also; however, it takes more time and patience.
    OTOH, if the sun is bright and the tinder is dry, it is probably quicker and easier on one's hands than a lot of other methods.
  17. LdMorgan

    LdMorgan Monkey+

    Usually, the larger the lens, the more energy collected and (with a good focus) the faster the tinder will light up.

    As an alternative to lenses, the reflector from any largish flashlight, 12V spotlight, headlight, etc. can be used as a fire starter.

    Just plug a little wad of tinder into the bulb socket (making sure it projects to the level of the bulb filaments) and point the reflector to the sun.

    Presto, Flame-o!

    Note also that a little wad of fine steel wool plugged into the socket will fire right up if there is still a a little electricity available--just load it up and hit the on switch for a moment.

    Pop the flaming wool out as quickly as possible and drop it into your bird's nest..

    You may cook the reflector a bit, but in an emergency, you'll get the fire you need.
  18. Tikka

    Tikka Monkey+++

    I have an old (80-100 years) old 3 7/8" magnifying glass with a metal frame and handle.
    I'm not sure what power it is; however, can see it has more than 5X and to the eye it appears to be more powerful than a 10x.

    It's large circle of heat starts fires easily; as it is so bright it also affects your eyes when you do. :D
  19. Hispeedal2

    Hispeedal2 Nay Sayer

    LOL. Like an early laser beam:


    "How hard is it to get some sharks with some freakin' lasers?"
  20. Tikka

    Tikka Monkey+++

    It has served as a death ray to cow ants. lol
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