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We've discussed many fire-starting methods here in the past—everything from matches to bow drills to fire pistons. However, thanks to the endless creativity of the human race, there are plenty of other methods for improvised ignition that we have yet to cover. One such device is the Fresnel lens.
You're probably familiar with the concept of starting a fire with eyeglasses or a magnifying glass. The general idea is to focus the sun's rays into a single point of light and heat atop your tinder bundle, and then wait for an ember to appear (if all goes according to plan). A Fresnel lens achieves the same result, but the design is quite different from an ordinary lens. This is because a Fresnel lens is composed of many angled segments, rather than a single large arc.
Without getting too much into the scientific content behind how a Fresnel lens works, we'll tell you why you should care. A Fresnel lens can be paper-thin. You can carry one of these lenses in your wallet in place of a business card, and have a means of starting a fire as long as bright sunlight and dry tinder are also available.
Emberlit gave us the business card fire lens seen above at the Outdoor Retailer show. It's the size and thickness of a standard business card, and it's even flexible. If you want one, they're included in the Emberlit fire starting kit, or you can buy value-packs of these lenses from various online retailers. They weigh almost nothing, so you can easily store them in your wallet, bug-out bag, glove box, and various other key locations.
So, now you know what a Fresnel lens is, but how easily can it start a fire? See for yourself:
Pretty effective, but it's also possible to take this concept to the extreme. One YouTuber removed the Fresnel lens from the surface of an old flat-screen TV, and turned it into a monstrous 2000-degree solar torch. Less portable, but a whole lot more powerful: