Make your own lava lamp

Published on October 23rd, 2012
Make your own lava lamp

It’s easier than you think…

What you need:

  • an empty one-litre plastic bottle
  • ¾ cup of water
  • a bottle of vegetable oil (you’ll need about 850ml)
  • food colouring
  • Effervescent tablets (such as Alka Seltzer)
  • A funnel
  • A torch (optional)

What to do:

  1. Pour the water into the plastic bottle.
  2. Slowly add vegetable oil until the bottle is almost full. Wait a few minutes for the two layers to separate.
  3. Add about 10 drops of food colouring.
  4. Add half an Alka Seltzer tablet (you can add more if necessary) and leave the bottle cap off.
  5. Watch your lava lamp bubble to life!
  6. Dim the lights and place over a torch for added effect.
  7. When the fizzing stops, you can add more Alka Seltzer, or just put the cap onto your bottle and store somewhere for future fizzy fun. All you have to do is open the bottle and add more Alka Seltzer to make your lava lamp start up again.

Why it works:
The oil floats above the water because it’s less dense. The two liquids don’t mix because one is polar and the other is non-polar (just like oil and vinegar in salad dressing).

The food colouring mixes with the water because it’s water-based, and the effervescent tablet is designed to dissolve as soon as it’s placed in water. As it dissolves, it creates bubbles of carbon dioxide, which take some of the coloured water with them as they bubble up through the oil. When a bubble reaches the surface, the gas escapes and the water sinks back to the bottom, where the cycle starts again.

Credit: Image from Flickr/Julia Franco