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Make Your Own Lava in a Glass!

It's not the red-hot stuff that comes out of volcanoes, but it's mesmerising to watch, completely safe, and you've almost certainly got everything you need in your kitchen. Parents, be warned: this might bring back fond memories of lava lamps!

What do you need?

  • Clear glass or plastic cup

  • ​Water

  • Vegetable oil

  • Food colouring

  • Salt

lava setup.JPG

Step 1

Fill your glass just over half full with water and add a few drops of food colouring. Give it a stir.

Step 2

Pour in just under a quarter of a cup of vegetable oil. Watch it settle into a layer floating on top of the water.

lava ready.JPG

Step 3

Sprinkle a good spoonful of salt into the glass and watch your lava start to bubble! Add more salt to keep it going.

lava go.JPG

What's going on?

It's all about density. Oil is less dense than water, so it floats on top. Salt is denser than both, so as it sinks it drags blobs of oil down with it. When the salt dissolves in the water, the oil is set free and floats back up to the top. Oil and water don't mix (scientists say oil is hydrophobic, which roughly means "scared of water"), so the oil stays in blobs as it rises, just like a lava lamp.

Looking for yet more fun?

Continue the investigation like a real scientist...

  • Try different oils, like olive or sunflower. Does the lava change?

  • How long does your lava keep going? Can you keep adding salt forever?

  • What's the best shape of glass for perfect lava: tall and thin, or short and wide?

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