Official Lava Lamp Dynamics Page
How a Lava Lamp Works
A lava lamp is filled with water and polyethylene glycol. Chlorinated
paraffin rests at the bottom of the lamp, and is heated by a light bulb.
The Cycle of a Lava Bubble
Before the lamp is turned on, the bottom of the glass bottle is covered
with paraffin to which just enough chlorine atoms are added to make the
wax slightly denser than water.
When the lamp is switched on, heat from the light bulb is transferred
to the paraffin via a coil of wire. The paraffin slowly melts, increasing
in volume by 3 percent and lowering its density.
Now slightly less dense than the very viscous water/polyethylene glycol
mixture, the paraffin blob slowly begins to float upward.
As the blob reaches cooler water at the top of the bottle, it begins
to shrink, and its density increases. So it sinks slowly to the bottom,
where the process starts over.
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