The Leidenfrost Ring is an aluminium ring that demonstrates the Leidenfrost Effect. The Leidenfrost Effect occurs when a liquid comes into contact with a hot object, with the correct temperature difference between the two.
For example, if you heat a frying pan to a temperature over 100 degrees Centigrade, but less than 160 degrees Centigrade, and then place a drop of water in the pan, the drop of water will boil and spit and turn to steam very quickly; at 160 degrees Centigrade, it is really quick!
However if you heat the frying pan to a temperature of 200 degrees Centigrade or more, you will then see the Leidenfrost Effect - place a drop of water in the frying pan and you will see that the drop of water floats around in the pan, hovering on a tiny cushion of steam, which is about 0.1mm thick. This cushion of steam effectively insulates the drop of water from the frying pan, and the drop will hover around in the pan for a surprisingly long time.
Our Leidenfrost Ring is made from solid aluminium, and has a pattern of ridges on the surface which cause the drop of water to move around the ring. The side walls retain the water drop inside the ring. You can experiment with slightly different temperatures and sizes of drop. It is even possible to have a loop of water spinning around in the ring.
For our demonstration, we placed the Leidenfrost Ring on a piece of mild steel, which provided some thermal mass, and placed the steel on an old baking tray, on top of a small gas powered cooker. The mild steel was painted with heatproof black paint, since the infrared thermometer we were using does not work on shiny surfaces like aluminium. It should also be possible to reach 200 degrees Centigrade in a domestic oven.
The Leidenfrost Ring is 42 mm in diameter. You will need to provide all the other equipment.
THIS IS NOT A TOY!
To stop the build up of limescale, it is best to use distilled water. There is a risk of burns from boiling water, steam and also the hot apparatus. You should use safety goggles when using this product. And also, if you place the Leidenfrost Ring inside a saucepan or a frying pan in order to heat it, make sure that the pan can take the heat.
There is an article about the Leidenfrost Effect here - www.bath.ac.uk/research/news/2015/05/19/leidenfrost-thermostat/
The Leidenfrost Effect is named after Johann Gottlieb Leidenfrost, who discussed this effect in a paper he published in 1756.