How a Lava Lamp Works

The Technical End Inspired by an egg timer, Edward Craven Walker spent months in his backyard perfecting the blend of waxes, oils, and solvents to come up with what he would call the Astro Lamp. The exact mixture of substances in commercial lava lamps is kept a secret, but the basic idea is simple. It's all about density.

• The colored wax is more dense than the fluid above, so it sinks to the bottom when the lamp isn't being heated.
• When the base of the lamp is heated, the wax expands and becomes less dense, so it floats to the top.
• As it floats to the top, it cools, becoming less dense, so it starts to sink back down again.

Home Chemistry
If you're feeling adventurous, or just want to understand the concepts behind lava lamps, you can make your own lamp at home. Instructions for varying levels of dedication can be found all over the internet. Here is a super-simple recipe that is guaranteed to delight kids and adults alike.

1. Fill a soda bottle 3/4 full of vegetable or mineral oil.
2. Add water, but leave a little room at the top.
3. Drop in 8-10 drops of food coloring.
4. Break up an Alka-Seltzer tablet into little pieces and add one by one.
5. When all of the tablets are broken up, put cap on bottle and shake gently back and forth in front of a flashlight. The tablets should attach to the liquid to form those beloved globs.