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Fresnel Lenses
Emergency Fire Starters for Wilderness Survival Kits
Small enough to slide in your wallet or purse.
Review by Thomas J. Elpel

      It is always sensible to have more than one means of starting a fire on you at all times. The Fresnel lens card magnifier is especially handy, because it is the size of a credit card and slips easily into a wallet or purse, glove box, or a wilderness survival kit of any shape or size. It is a multipurpose tool that can be used to read small type, magnify flowers for identification, or to start a fire.

      The Fresnel lens functions like a regular magnifying glass, except it is flat instead of lens-shaped. It is named after its inventor, French physicist Augustin Jean Fresnel, who studied light and optics in the 1800s. Basically, if you were to slice a normal lens into a hundred or more concentric rings (like the rings of a tree), and then mount each of those rings on a flat surface, then you would have a flat lens of equal power to the original lens. The face of each ring is a slightly different angle to retain the lens' ability to focus light towards a central point. A Fresnel lens can be made as large as desired, without making it thicker and thicker, as you would with a regular lens. Fresnel lenses were first used in lighthouses to focus the beam of light far out across the ocean throughout the nights.

      Starting a fire with a Fresnel Lens card magnifier is just like using a regular magnifying glass. Collect a wad of dry, fluffy tinder, such as the dry inner bark of a dead cottonwood, and focus the light of the lens on the tinder to start it smoldering. When you have a glowing coal, then you can blow on it to make it grow until it ultimately bursts into flame. Do keep in mind that card magnifiers only work when the sun is shining. They don't do much at night or in the rain.

      Most card-sized magnifiers are 3x power, but ours are 5x lenses, concentrating solar heat better for even easier fire-starting.

Also see these related pages:
The Always-With-You Compact Survival Kit
Flint & Steel Kits for Primitive Fire Making
Bowdrill and Handdrill Sets for Primitive Fire Making
Fire Plow Sets for Primitive Fire Making
Fire Pistons for Primitive Fire Making
Swedish Fire Steel Emergency Fire Starter