How Does a Lava Lamp Work?

by Johnny Luxembourg

In a lava lamp or liquid motion lamp are liquids which are very close in density and insoluble in one another.

The lava lamp has an illuminating bulb, a glass bottle which contains a transparent oil and translucent wax, and a metallic wire coil in the bottom of the glass bottle.

The glass bottle is placed on top of the bulb, which heats the contents. The wax is denser than the oil at room temperature, and slightly less dense than the oil under warmer conditions. This is because the wax expands more than the oil when heated.

The heavier liquid, the wax, absorbs the heat, and as it heats up, it expands. As it expands it becomes less dense. Because the liquids have very similar densities, the formerly heavier wax is suddenly lighter than the liquid around it, so it rises in blobs.  As a blob rises away from the heating bulb, it cools, making it denser and therefore heavier, so it sinks back down again.

The wire coil in the base of the bottle acts as a surface tension breaker to recombine the cooled blobs of wax after they reach the bottom again. The underlying mechanism is a form of Rayleigh Taylor instability.

What are the exact chemicals in the glass bottle?  The recipe is a trade secret, only the manufacturers of lava lamps know the exact ingredients. Like the secret formula for Coca-Cola, scientists can analyze and approximate the chemicals but can not duplicate the exact recipe.

However, you will find many sites on the internet that can teach you how to build your own lava lamp.  It is not cheap and it's probably cheaper to just buy one at the store, however if you want to feel the satisfaction of accomplishing your very own liquid motion lamp, do an online search for "The poor man's lava lamp", "Make your own lava lamp", or "Turpentine lava lamp".  

How dangerous is a lava lamp?  Probably not much, unless used improperly. 

Cases have been reported of people heating lava lamps on their stoves, to speed up the time it takes for a lava lamp to be hot enough to start dancing I suppose.  As can be expected, steam would build up inside and the lava lamp exploded, in one case killing a 24 year old with a shard of the flying glass. 

Always use only the supplied base with its bulb to heat up a lava lamp.   It can take up to 60 minutes after being switched on, for a lava lamp to start doing its magic.  But it's worth the wait :)