How to Build a Long-Lasting Lava Lamp

By Paul Dohrman

Lava lamps essentially are filled with heated wax that floats to the top of a saline solution, cools and contracts, and drops back down again. The varying sizes of the pieces of wax means they are of varying density, which means they are of varying buoyancy. This is what drives the periodic motion of the wax. You can build your own easily maintained lava lamp using rubbing alcohol and mineral oil. Like salt water and wax, they, too, are similar in density and do not dissolve into each other over time.

Choose a bottle before you choose a stand—the aluminum pot—on which to place it. A tall, slender clear-glass bottle with a screw top works best. Using a tall, slender bottle will help maintain a wide temperature differential between the heated bottom region of the lamp and the top, where the mineral oil will cool and contract. A gallon wine jug also will work, although it is a bit wide for efficient heat dissipation.

Use the nibbler tool to cut a square hole in the bottom of a thin-walled, aluminum pot, small enough so the bottle can't fall through. A square will keep the bottle from falling through and is easier to cut than a circular hole.

Cut a small, triangular notch in the lip of the pot, large enough to accommodate the lamp socket's cord. The notch will allow the upside-down pot to lie flat and make the lamp more stable.

Plug a manual dimmer into an electric wall socket. Plug the lamp cord into the dimmer. Screw the bulb into the cord’s socket. Don’t turn on the light just yet. Place the bulb under the upside-down pot, with the cord threaded through the notch you made in Step 3.

Pour mineral oil in the bottle until is it one-eighth full. Add enough 90 percent rubbing alcohol so the bottle is three-quarters full. Adding the alcohol will agitate the mineral oil, so let the oil settle for two or three hours. After the oil has settled, turn on the bulb for an hour to heat the mineral oil before proceeding to the next step.

Add 70 percent rubbing alcohol by small increments, waiting 10 minutes between additions to let the concentration even out. Keep adding 70 percent alcohol until the oil starts to rise.

Add small amounts of distilled water in 10-minute intervals. Make sure there is an air gap of an inch or two at the top, otherwise, the oil might not be able to expand enough to float. Dip a drinking straw into a glass of water, hold a finger over the top of the straw so the water stays in the straw and pour about half the water in the straw into the lamp each time. Stop adding water when some of the mineral oil rises to the top. The liquids' densities are now correctly balanced and you can screw the cap on the bottle.

Tip

If the mineral oil forms a dome but never rises, there might not be enough of an air gap in the bottle for the oil to expand. Remove some fluid with a turkey baster to make a bigger an air pocket. If that doesn’t work, the bottle may be heating too quickly. Lower the dimmer switch and try again, starting from Step 5.

Warning

Don't shake or stir the mixture to speed up the evening out of the alcohol concentration. Shaking the bottle could break up the mineral oil and make finding the right density of alcohol even harder. It could take hours or days for the oil to resettle so you can try again.

Use common sense when working with a flammable liquid such as rubbing alcohol.

About the Author

Paul Dohrman's academic background is in physics and economics. He has professional experience as an educator, mortgage consultant, and casualty actuary. His interests include development economics, technology-based charities, and angel investing.