Common sense would tell us that plastic burns and melts if touched or influenced by fire or heat, but this survival technique proves that you can actually boil water inside a plastic vessel put over a fire with no structural damage.
What would happen if you suddenly find out that the metallic vessel that you used to cook things or boil water in your camp is suddenly lost or damaged beyond repair? Some pessimistic folks would think that there would be no more hot meals or even worse: that it would be impossible to purify more water by boiling it. However, that is not true: You can actually heat and even boil water inside a plastic container by putting it over a fire much like a kettle. The principle is simple: The water inside the vessel will absorb all the heat or energy transmitted by the flames to the plastic; hence, the container suffers no damage.
Believe it or not, you can cook this in a plastic bowl too.