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Homemade Lava Lamp

Ages 5+ with an adult10 minutesMess: Medium: work on a tray
Grown-ups: please supervise this experiment the whole time. Read the safety notes first.

Make a bubbling potion bottle from oil, water, food colouring and a sprinkle of salt.

WOW FACT

The first lava lamp, the Astro, was launched in Britain in 1963 by inventor Edward Craven Walker. Real lava lamps use heat from a bulb instead of salt.

🧰 What you'll need

A clear plastic bottle with lidAbout 500 ml, rinsed out.
✔ You probably have this
WaterStraight from the tap.
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Vegetable or sunflower oilFrom the kitchen cupboard.
✔ You probably have this
Food colouringAny colour.
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Table saltAbout a teaspoon at a time.
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A trayTo catch any spills.
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A torchOptional, for a spooky glow.
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✨ Want to go further? (optional)

Kids' chemistry setMore safe experiments about mixing and floating.
View on Amazon (amazon.co.uk)
Plastic science beakersMeasure your oil and water like a real scientist.
View on Amazon (amazon.co.uk)
Children's science experiment bookDozens of easy experiments for rainy days.
View on Amazon (amazon.co.uk)

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What to do

  1. Stand the bottle on the tray and fill it about a quarter full with water.
  2. An adult pours in oil until the bottle is about three-quarters full. Wait for the oil to settle on top.
  3. Add a few drops of food colouring. Watch the drops sink through the oil and colour the water.
  4. Sprinkle in about a teaspoon of salt and watch blobs sink down, then float back up.
  5. Add more salt each time the bubbling stops.
  6. Shine a torch through the bottom for a spooky glow. When you've finished, screw the lid on tight.

What's going on?

Oil and water don't mix: scientists call them immiscible. Oil is less dense than water, so it floats on top. Food colouring dissolves in water but not in oil, which is why it passes through the oil and colours only the water. Salt is denser than both, so it sinks and drags blobs of oil down with it. In the water the salt dissolves, lets go of the oil, and the oil floats back up to the top.

Safety notes