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Here’s How You Can Start a Fire Using a Sandwich Bag Filled With Water

How exactly do you start a fire without matches or a lighter? Basically, the sandwich bag acts like a magnifying glass and harnesses the power of the sun to create an intense heat.Grant Thompson – the King of Random – teaches us how to start a fire with a Sandwich bag. And we tried to melt glass in my backyard.

image/text credit: Veritasium

Thompson shows how filling a small plastic back with water and twisting it to create a sphere can be used as a magnifying glass. Using some crushed up dry bark as a fire starter, Thompson expertly gets the bag to concentrate heat enough to create an ember before transferring that to a nest of tinder made of dry grass and then finally onto a pit with kindling ready.

The whole process is very interesting and the short video makes it seem very doableThe intensity of sunlight on Earth is about 1300 Watts per square meter.When you focus the sun’s rays using a magnifying glass (or in this case sphere of water) you can increase the intensity roughly ten thousand fold.


This increases the temperature of wood to its autoignition point starting the reaction with oxygen in the atmosphere. By protecting the hot embers and adding more energy and fuel, you can get these hot coals to start a roaring fire.