What you need to prepare
- A small Cup with a round bottom, can bowl.
- A piece of dry paper.
Pour in a Cup of water and put in freezer. When water turns into ice, take a Cup and put it in hot water. After some time the ice separates from the Cup.
Now go out on the balcony, put the piece of paper on the stone floor of the balcony and a piece of ice focus the sun on a piece of paper.
Paper charred, because in your hands is not just ice, and magnifier.