A magnifying glass is great for starting fires. As long as the sun is out! It works best with dry tinder like shaved wood, crunched dry leaves, etc.
I do keep a survival magnifying glass in each one of my kits. That’s along with several other methods to start a fire like a lighter, matches, magnesium fire-starter, Vaseline cotton-ball tinder, and more…
[ Read: Fire Starter Kit List ]
A magnifying glass will light a fire in seconds. That’s under ideal conditions. How long it takes will vary depending on the time of day, angle of the sun, the efficiency of the magnifying lens, and the tinder being used.
The quality of the glass (which is often plastic) can make a noticeable difference. The ability to focus a tiny bright spot onto the tinder so as to ignite more quickly.
Can a plastic magnifying glass start a fire? Yes, plastic lenses will work. However some of the cheap ones are simply too poorly manufactured to focus a concentrated beam from the sun. Glass or quality acrylic will be better.
With that said, most every plastic lens I’ve tested as a ‘survival magnifying glass’ worked. It just takes a bit longer to get a fire going. Again, depending on conditions.
Does the diameter of the magnifying lens make a difference starting a fire? In my experience, not so much of a difference. Although a larger diameter lens will pick up more available light and is quicker and easier to start a fire.
A word of caution (besides the obvious when making fire) is to avoid looking at the concentrated point of light, which could damage your eyes. It can be very bright! Sunglasses?
How Does A Survival Magnifying Glass Work?
What’s the science behind lighting a fire with a magnifying glass? Well, it’s about the photons. Photons are the particles that carry visible light from the sun to the earth. They also contain energy in the form of heat. Through the use of a magnifying glass, the path of these photons are narrowed to a highly localized area (the dot of light that passes through the convex shaped lens). This results in a concentration of heat that can reach incredibly high temperatures. If a high enough temperature is reached (somewhere around 450 degrees F), the tinder or kindling will smolder and begin to burn.
Most magnifying glass are not expensive at all.
My recommendation? This one. Compact. Leather sheath.
Folding Pocket Magnifying Glass
(view on amzn)
[ Read: Fresnel Lens For Your Wallet ]