In the heat of summer, roadside brush fires are frequently attributed to fluid-filled bottles that concentrate the sun’s rays onto dead grass or other tinder material. Apparently, kindling a fire this way is so easy any litterbug can do it—but could I light a fire this way on purpose? This one has bugged me for years, and I finally decided to give it a shot.

Water bottle fire starting is all about creating a lens (like a magnifying glass) and concentrating the heat from sunlight onto tinder. For the best chance of success, the water in the bottle should be crystal clear, and the round shoulder of the bottle should be clear, smooth and un-textured. This is supposedly why many bottle manufacturers pay a little extra for a textured bottle, so their product doesn’t get bad press from being the cause of destructive wildfires. You’ll also need some top-quality tinder. Char cloth is ideal, due to its low ignition temperature and dark, light-absorbing color. But for my experiment, I used birch fungus powder.

I went to work on a sunny yet breezy afternoon. After blinding myself periodically with the shimmering light reflecting off the shifting water inside bottle, I realized that the bottle needed to be dead still (and that I needed sunglasses). I’m sure this combination of water, plastic, light, and tinder creates flame by accident all the time, but this was the most frustrating thing I have ever tried in the name of OL Survival. Sweat rolled into my eyes and stung them as the sun played peek-a-boo behind the clouds. For many minutes, the best result I could summon was a fleeting wisp of smoke.

Patience was failing and I was getting close to throwing the BS flag when a small, smoking spot remained smoking in my pile of birch fungus tinder. And there it was: fire from water (and light).
So this does method does indeed work with a plastic water bottle, strong sun, clear water, and top-shelf tinder. But even though it’s possible, I wouldn’t bet the farm on it in a survival situation. To me, it’s just one more reminder to always carry a few Bic lighters.