This is one of the most fun ways to start a fire, but it is limited to sunny days and to the need for having a magnifying glass on you at all times. There are some other items that can work, but we will just have to get the basics down first, and then delve into alternatives.
What you Need.
- The Sun (or an ultra-powerful light source)
- A Magnifying Glass (or something that can focus the waves of light)
The Principle Behind Success.
When you pick up the magnifying glass you are really picking up a convex lens (a lens where the middles are thicker than the edges). The main purpose of the convex lens is to gather light waves and concetrate them. The image on the right exemplifies this.
Using the picture on the right, let’s imagine that the sun’s light waves are the blue lines. The waves from the sun are starting on the right side of the picture and traveling toward the left. To get the most waves concentrated in a single area (the most heat) you will need to adjust the focal length to create the smallest dot of light that you possible can. The smaller the dot of light, the more concentrated the heat and the higher the likelihood of transfer enough heat to start a fire.
It takes some practice to concentrate the light, and I would encourage you to give it a try on something flat – like a sheet of notebook paper.
Applying it in the Wilderness.
Up to this point tinder has been collected into a bird nest structure to better catch the spark. In this method, you will still want your bird nest, but you will not be holding the magnifying glass over this. Instead, you will want to find a flat, dry and thin object that will accept heat easily (paper, leaf, etc.). You will hold the magnifying glass over this flat item until you get a good spark or even flame. Then you will transfer the spark or flame to the bird nest of tinder.
It is really as simple as that. If you happen to be in a sunny area with a magnifying glass, this is a great way to start a fire.
If you are looking for a strong, compact magnifying glass check out the Carson® MagniFlip 3x Flip-Open Pocket Magnifier with Built-In Case (GN-33). This little gem is about $5 at Amazon.com and is 2″ squared in size and 0.5″ thick. It is a perfect companion at all times.
Alternatives to the Magnifying Glass.
Sometimes you will out in the wild without a magnifying glass, actually that happens more often than not. However, there are a few items that you might have on you that can double as a magnifying glass:
- Removable Camera Lens – the lens that snaps onto Single Lens Reflex Cameras do a great job of focusing light.
- Your Reading Glasses – Convex lenses are used in bifocals. You can take either lens of your bifocal and use it to focus the light.
- Your Compass – Many compasses have magnifying glasses built in to help read the map. It is actually smart to look for a compass with this built-in feature.
- Get Creative – If you drink just the right amount of water out of your water bottle, you can utilize it to focus light by holding it at an angle. There are plenty of other fixes and tricks.
Be sure to share any tricks or alternatives that you have found to work.