Everyone gets the same wonder and curiosity when seeing a lava lamp in action, but how does it work? Well, the mechanisms involved are centred around the idea that denser fluids settle under lighter ones.

What this means is that for a particular volume if two fluids are present, that do not interact, then the heavier fluid will come to rest under the less dense one. This is the same principle that makes oil float on water or honey sink to the bottom of a cup of water until it is mixed.

Now to replicate this process we will need a bottle of water, vegetable oil, food colouring and some fizzing tablets such as Alka Seltzer. Fill the bottle with the vegetable oil until it is roughly three-quarters full, the rest of the bottle can be filled with tap water. It will take a few minutes for the two fluids to settle. Since the oil is a lighter fluid, it will rest on top of the water.

Whatever colour you are using, place enough of it in for the water to blend into that dye colour. This may need a little mixing. To reproduce the fizzy bubbles that we get with a lava lamp, we need a way to raise small sections of the water above the oil.

This is where the fuzzing tablets come in, drop one in. The tablet will sink to the bottom of the bottle and the bubbles will push the coloured water to the top part.

To make it even closer to the genuine article, you can shine a flashlight through the bottom of the bottle. Real lava lamps work roughly in this way, except instead of using fuzzing tablets they use wax instead of water and water instead of oil. Through small changes in temperature between the bottom and top of the container, the wax changes its density and thus floats to the top until it cools and drops to the bottom again.

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