As of 2014, the liquid ingredients in lava lamps are considered a trade secret, but until 1970, patents showed that they were made with paraffin wax, water, mineral oil and carbon tetrachloride. Whatever the current ingredients are, they are heated by a light bulb in the base of the lamp.
The ingredients of lava lamp liquid changed around 1970, when carbon tetrachloride was found to be toxic. No matter which ingredients are used, the lamp works the same way. The light bulb heats both the liquid mixture and the blob of wax material settled on the bottom. As it heats, the waxy blob becomes less dense than the liquid and begins to rise to the top of the lamp. As it moves away from the heat source, it begins to cool and descend to the base, where it is heated and rises again, thus forming the cycling waves of blobs. Colored dyes are used for decorative effect.