A Groovy Experiment on Density: Lava in a Glass

Learn how to make lava in a glass!

Lava lamp
Story Blocks

Learn how to make lava in a glass!

Remember those retro lava lamps with bright colors bouncing around? Well today we’re going to make our own!

For this experiment you’ll need:

  • A clear glass filled with water
  • ¼ cup vegetable oil
  • 1 tsp salt
  • Food coloring (optional)


  • Fill the glass about ¾ full of water
  • Add about 5 drops of food coloring
  • Slowly pour the vegetable oil into the glass – noticing how it floats to the top
  • Sprinkle the salt on top
  • Watch the lava slowly move up and down

So what’s really going on here?

It’s all about density! The oil floats on top of the water because it weighs less… -- it’s less dense. The salt, however, is heavier than the oil, so it sinks down into the water, grabbing some of the oil with it.

But what happens to salt in water? It dissolves! So the salt dissolves and the oil floats back up to the top.

Contact Us