The fresnel lens received its name from French physicist Augustin-Jean Fresnel who developed the compact lens for use in lighthouses.
What makes this lens different from a conventional lens? They are much thinner than conventional types and they can even be formed into a flat shape.
Today these small, flat, compact lenses are often produced to resemble the shape of a credit card which makes them ideal for survival kits.
The concept is pretty simple. They're flat on one side and the other side contains several small ridges which are actually rings that focus the light towards the middle.
The design allows you to gather light from the sun and focus it into a small concentrated beam which under the right conditions can be hot enough to light a fire.
Commonly referred to as a credit card magnifier, their lightweight, compact design allows you to place them in your wallet, tackle box or anywhere else you desire. Plus, they're cheep! You can purchase one for roughly $1 - $2 and they can be found online or at many outdoor department stores.
While most models have a 2x or 3x magnification, 4x or even 5x models are available which makes starting a fire a little bit easier.
The main problem with using a fresnel lens to start a fire is the sun's availability.
Since they require the sun for operation, they only work on a sunny day…..preferably when the sun is at its highest point. So, on a cloudy day or at night they're pretty much worthless.
You should never choose this type of fire starter as your primary survival fire starting tool. However, they're a great addition to any survival kit and it can be a fun and entertaining way to light a fire.
Assuming you are attempting this on a sunny day, start by gathering a supply of dry grass, pine needles and small sticks to use as your tinder bundle.
For best results, try to line up sun, lens and tinder bundle so you can gather as much sunlight as possible. The more direct sunlight you can focus through the lens, the more intense the light will be.
Rotate the lens from side to side and adjust the distance between the lens and tinder bundle until you focus the light into the smallest beam possible.
When done correctly your beam of light will be about the size of a penny and will be almost white in color.
Using a steady hand you should begin to see smoke in just a few seconds. Even though you see smoke initially, the tinder bundle won't burst into flames. In fact, a majority of the time you'll just get a small ember to form. Once you see the ember, gently blow on the ember until it lights the tinder bundle.
To light a fire with a fresnel lens use these helpful hits to get the best results:
- Choose a lens with a 4x or 5x magnification
- Use dry tinder
- Attempt this on a sunny day when the suns at it's highest peak
- Keep a steady hand and focus the light into the smallest beam possible
Even though you're at the mercy of mother nature, a credit card magnifier will work to start a fire.
While you shouldn't rely on them as your primary method of starting a fire, their compact and lightweight design along with being inexpensive makes them a welcome addition to any survival kit.