Starting a fire with water may seem counterintuitive, but water is actually a very useful tool for starting fires in emergency situations if no other options are available.
Here are 4 simple ways to use water to create a sphere or lens which can be used to concentrate sunlight and make a fire starter, and one method that utilizes the reaction between water and sodium as a way to start a fire on a cloudy day. These come from The King of Random on YouTube.
1. Light bulb
Hollow out the bottom out of a light bulb and rinse it several times with water to remove the powdery residue. Refill the bulb with water and cap the end with a balloon. You now have a makeshift magnifying glass that should ignite paper within seconds.
2. Plastic wrap
Create a liquid sphere by lining a bowl with plastic wrap and filling it with water. Gather the corners of the plastic wrap together and twist to form the sphere.
3. Picture frame & plastic wrap
Cover a picture frame with a layer of plastic wrap and suspend it off the ground. Pour hot water on the plastic until it sags, forming a liquid lens.
4. Juice bottle
These bubble-shaped juice bottles work great as magnifiers when filled with water.
5. Sodium and toilet paper roll
This method requires no sun. Using a small amount of sodium, a toilet paper roll, and some kindling, a blazing fire can be created in seconds.
See all of these methods in action in this video. Being able to start fires this quickly and efficiently may take some practice, but these are good skills to know for emergency situations.