Stranded on a deserted island or in the wilderness? Starting a fire is an essential survival skill. All you need is a discarded water bottle which sadly enough will be all over the place and a little patience and you can create a spark. Any kind of water bottle will do, but transparent bottles are the best because colored bottles absorb some of the intensity of the sunlight.
You will need to make sure the bottle is filled with liquid (water preferably). The size of the bottle doesn’t really matter, but the top portion should be smooth and rounded. The piece of paper you will require should not be all white because white reflects light. A bit of writing on it is essential. If you only have white paper, just rub a section of the paper into the darkest dirt you can find.
Fold the piece of paper with the black ink on it so that the writing is exposed where the heat will be focusing. This will serve as your platform. Remove the label from the bottle. Use the convex edge of the water bottle. This will act as a magnifying glass which refracts the sunlight. Focus the bottle on the black portion of the paper. You might need to do a little shifting in order to find the precise point where the majority of sunlight is concentrated. In a few seconds the area should start to smoke. Keep the light focused on that area until a hole begins to burn and grow to the size of a quarter. Start added other pieces of torn paper and blow into the embers until a flame is ignited. VOILA!!! You now have fire.
This is an excellent DIY survival tip. You can even use a water filled sandwich bag instead of a water bottle. It takes time to perfect the technique, so you should probably start practicing and not wait for an emergency to arise.