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Experiment

The DIY Lava Lamp

Drop fizzing tablets into an oil-and-water jar to create slow-motion coloured blobs that rise and fall like a real lava lamp.

Ages 6–1015–30 min1–3 kids

Fill a clear bottle mostly with vegetable oil and a little coloured water, then drop in pieces of a fizzing tablet to watch coloured blobs rise and fall through the oil in a slow, mesmerizing bubble show. Add more tablet pieces to keep the effect going as long as interest lasts.

What you need

  • a clear plastic bottle or jar
  • vegetable oil
  • water
  • food colouring
  • an effervescent tablet (like an antacid tablet)

How to do it

  1. 1Fill the bottle about three-quarters full with vegetable oil.
  2. 2Add a small amount of water mixed with a few drops of food colouring.
  3. 3Break an effervescent tablet into a few pieces and drop one in, watching the fizzing blobs rise and fall.
  4. 4Add more tablet pieces whenever the fizzing slows, keeping the show going.

Variations

  • If the effect fades quickly: give the bottle a gentle swirl between tablet drops to redistribute the water droplets.
  • How it ends: capping the bottle and setting it on a shelf as a calming decoration is a satisfying way to keep the project going after the play session.

💡 Parent tip

Keep the finished bottle capped tightly and sealed if a younger sibling is around, and store it somewhere it won't get knocked over.

What your child develops

  • Density and immiscibility — a hands-on demonstration of why oil and water don't mix
  • Chemical reactions — the fizzing tablet's reaction with water is a safe, visible chemistry lesson
  • Sustained visual attention — the slow, unpredictable motion has a genuinely calming, focus-building effect

Safety notes

  • Keep tablets out of reach of younger children, and supervise closely if the tablet type is intended for adult use only.

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