FeatherSticks · Fire

How to Start a Fire with a Magnifying Glass (Sun Fire)

No spark, no fuel, no noise: just sunlight and a piece of glass.

Quick facts

Time: A few seconds to about half a minute with char cloth in strong sun
Difficulty: Easy in summer sun, hard or impossible in haze and winter
Best for: Sunny days, saving matches and fuel, quiet practice
You need: Magnifier or Fresnel card, dark tinder, tinder bundle, backup lighter

1 Check the sun

You need strong, direct sunlight, ideally around midday. If your body casts a sharp shadow, the sun is strong enough to try.
2 Prepare tinder and nest first

Lay char cloth or other dark tinder on a piece of bark, and have a tinder bundle and kindling ready before you start focusing.
3 Hold the lens square to the sun

Tilt the lens until it faces the sun directly. Its shadow on the ground should be round, not stretched.
4 Find the smallest dot

Move the lens slowly up and down until the patch of light shrinks to its smallest, brightest dot on the tinder.
5 Hold steady until it glows

Brace your hands and keep the dot still. Char cloth smokes within seconds; wait until a glowing spot spreads by itself.
6 Blow the ember into flame

Put the glowing tinder into the nest, fold it loosely, blow long steady breaths and set the flaming bundle under your kindling.

Trying in haze, thin cloud or low evening sun, when there is too little direct light.
Holding the lens slightly out of focus, so the dot is a warm orange patch instead of a tiny white point.
Aiming at pale tinder such as cotton wool or dry grass that reflects most of the light.
Tilting the lens away from the sun, which stretches the dot into a weak oval.
Looking at the sun through the lens or staring at the bright dot instead of glancing briefly.
Leaving a lens or water bottle lying in the sun in a car, a tent or on dry grass.
Relying on a lens as the only fire method and carrying no ferro rod or lighter.