I'm looking for a magnifier for my survival kit

I want to give myself a variety of options for making fire. I already have a flint and a lighter. Now I'm trying to find a pocket-sized acrylic magnifier (I don't want glass because it might break).

Is there a minimum magnification level you need to start a fire?

The amount of infrared energy (a.k.a. heat) that can be focused to a point depends mostly upon the surface area of the magnifier lens, not its magnification power. You can have two magnifiers with the same surface area and different powers, and you will have identical results… the only difference is that you will hold one magnifier closer and one farther away when focusing the point of light.

The best bet is to get a good acrylic Fresnel (flat, with the visible concentric rings) magnifier in the biggest size (surface area) that your desired kit will accommodate.

Actually, the higher magnification works better, as far as it's focus length is not too short to burn the lens when tinder ignites. But JCWohlschlag is absolutely correct that the lens diameter (surface area) is a more significant factor.

I'd recommend something not higher than 5x (2 inch focus). The physics behind this is simple. The shorter the focus distance (higher magnification) - the smaller the spot where the energy from the Sun is concentrated (and so higher the temperature).

I have had success buying from these folks 3Dlens .

Check these out. They are only a dollar a piece. I have several and they work fairly well. With the case its about the thickness of a credit card.

http://www.bestglide.com/fresnel_lens_firestarter.html

My magnifier is a glass one that swivels into a leather case.

Sue

CityBoy,

Wow, a bunch of responses and not one "welcome, newguy!".

So, welcome to the fire newguy!

-Blast, who uses a credit-card sized fresnel lens picked up at a bookstore

haha

Thanks for the welcome. Although since I didn't introduce myself either, I guess a welcome was not quite mandatory.

Ah, got caught! I didn’t even notice your post count. Welcome to the forums, newguy!