In 1787 Jacques Charles discovered that a gas volume is proportional to its absolute temperature, or in other words, as the temperature increases, the volume will increase. This became known as Charles’ Law, and it explains to us how this amazing Hand Boiler works.
In a closed container, as the temperature rises, so does the pressure. As the temperature increases, the molecules of gas in the container move faster, which increases the pressure. As the pressure increases in one of the chambers, the liquid will be pushed into the other chamber, thus creating a stunning liquid display.
Conversely, as the air in one of the chambers cools off, the moving molecules of gas slow down, lowering the pressure. The liquid will move from an area of higher pressure to an area of lower pressure.
