When the gas in the bottom bulb is heated with your hand, the increase in temperature creates an increase in air pressure. This increased pressure pushes the liquid up the tube to the top bulb.
When all of the liquid transfers from the bottom bulb, air bubbles are forced up the tube, causing the liquid in the top bulb to appear to “boil.”
This item ships in randomly selected assorted colours based on availability.
Recommended Ages 6+