Budget Prep: Fresnel Lens
An Alternative Way to Harness the Power of the Sun
Inspired by prepper Dan Roja's solar survival station, but lack a 20-year-old rear-projection televesion set that houses a large fresnel lens? We're bringing you budget versions of the preps inspired by our very own season three prepper builds.
Magnifying Lens, an Abundant Alternative
Not sure about you, but I don’t have access to a 20 yr. old rear-projection television set where I can remove the huge 3’ by 5’ Fresnel lens out of the back of it to heat water or start a fire. But I do have access to a magnifying glass, and in a survival situation, it could work in the same way as a smaller Fresnel lens.
Remember as kids when we would take a magnifying glass outside and use it to use burn leaves on the sidewalk, or if we got bored; ants? (FYI: this is no longer an acceptable practice.)
Magnifying glasses come in a plethora of sizes and strengthens; and they are something you should have with you at all times, either in your vehicle, handbag, go-bag, diaper bag, caches, kitchen drawer, office drawer, lunchbox and so on and so forth.
How to Start a Fire Using a Magnifying Glass:
You may have heard the quote, “good things come in small packages.” This definitely holds true for a magnifying glass. It can be used to read things up close if you misplace or break your reading glasses, identify a plant or insect out in the wild, read the fine print on labels of first-aid meds or preps, remove a thorn from a body part, thread a needle, tie a fishing knot, or make intricate repairs. What we are going to demonstrate with our magnifying glass is how to start a fire - for cooking, boiling/sanitizing water and for light (campfire – torches) just as a Fresnel lens does.
Start by gathering your tinder. This can be wood shavings, dead grass, fallen leaves, tree bark, newspaper, or a paper napkin; just make sure it is dry. If the tinder feels damp to the touch, then it probably is. If you can’t find any dry tinder, you can put the tinder in your pocket and the heat from your body may help dry it out.
When arranging the tinder, start with your finer material on the bottom first, then stack small twigs in a teepee like fashion over the finer tinder material. Then you can stack larger twigs on the teepee, making sure not to pack it too densely or you won’t get enough oxygen and your heat transfer will not be sufficient. Remember you need heat, fuel and oxygen to create a fire – not just heat.
For that reason, it is often times best to ignite a small batch of tinder outside of your teepee structure, and then once it starts to smolder and flame, move it to the teepee area to ignite the main fire.
Save your larger sticks off to the side, and add them to the fire, only after you get the fire started.
Before starting a fire, make sure you have a way to put it out. Keep a bucket of water, a fire extinguisher, or both on hand.
Once your tinder is arranged, angle the lens so that the sun light passes through it and then concentrate the point of light (the sun shining through the lens) on your tinder. The “sweet-spot” should be a very bright circular dot – the smaller the circle, the more the heat is concentrated on the area.
There is something of an art to making a fire with a magnifying glass. You need to find the “sweet-spot” of the sun’s rays through the glass and onto your tinder to generate heat and subsequently a fire.
Hold your magnifying glass still until the “sweet-spot” turns into a small flame. Blow gently on the flame to help it spread; and, once the tinder is burning slide it over to your teepee structure to ignite that. As needed, you can add larger twigs and sticks.
Another option to fire starting is a miniature Fresnel lens. You can actually get a small wallet-sized Fresnel lens for as little as a dollar each. This small 2”x 3” plastic cards work under the same premise as the magnifying glasses.
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