What's inside a lava lamp? --- David, Salamanca, N.Y.
Marshall Brain Answers:
Start by taking a look at How Liquid Motion Lamps Work. What you learn in that article is that there are two fluids in a lava lamp that are: a) don't dissolve into one another (in the same way that oil and water don't dissolve into one another), and b) are very close in terms of density. The density needs to be so close that they start out with one fluid lighter than the other, and after the addition of heat those densities reverse so the lava rises.
Although the actual chemicals inside a lava lamp are a trade secret, this page talks about experiments that have been done to try to replicate the formula. The liquid is distilled water with enough salt added to get the density exactly right, and the lava is a mixture of paraffin wax and perc (see How Dry Cleaning Works for more information on perc).
This video walks you through the steps described in the article:
In the video, the Brakleen is pure perc (Perchloroethylene).