The principle of the lava lamp is very simple. There is a high-power light bulb in the base. The bottle body is made of a sealed glass bottle, which contains transparent liquid and translucent colored liquid wax. The density of liquid wax at room temperature is slightly higher than that of liquid, and it is still below when it is not heated. After the lamp is turned on to start heating, the density of the liquid wax is slightly lower than that of the transparent liquid, and the phenomenon of thermal convection makes the liquid wax move up and down like lava. In addition, some manufacturers will put a coil spring in the liquid wax to change the effect of the liquid wax change.

After power-on, the bulb in the base heats and seals the glass bottle, and transfers the heat to the liquid wax. The volume of the liquid wax in the bottle gradually expands, and the liquid also expands, but the expansion coefficient of the liquid is small. After heating for more than ten minutes, the liquid wax gradually expands. The ground will float upward. When it is about to float to the surface of the water, the liquid wax gradually cools down, the density increases and sinks to the bottom of the bottle, causing the changing light and shadow effect over and over again. However, if it is heated for too long, all the liquid and liquid wax in the glass bottle will be heated, and the entire liquid wax will float above the transparent liquid.