Fireworks In A Jar!

JoFamily Life, Science Fun

Water and oil in a jar with food colouring dripping through the layers

We enjoy simple science experiments in our house, and the idea of making ‘fireworks’ whilst sharing a love of the subject is one not to be missed. It is a great activity for a rainy weekend day, or a bright sunny one – there’s no reason why this can’t be done in a garden or with the windows thrown wide.

The idea behind it is a simple one of liquids mixing – or not. It is something that has engaged my boys from a very young preschool age through to now (my eldest fast approaching 11). We call it: fireworks in a jar.

The science bit!

Oil and water don’t mix, and this is an experiment in density (oil being less dense than water) as much as it is mixing. The primary point is that they stay separate. You can make your own oil tubes or sensory bottles to get this effect too.

Fireworks in a jar, goes one step further than just noticing the separation of the oil and the water, by adding in a third ingredient – food colouring. The food colouring is heavier than both the oil and the water, so will ‘fall through’ the oil layer in small drips. This creates the firework type effect in the water as it falls down to the bottom of the jar.

One word of warning though – if you use water based food colouring then the colour and the water will mix. We were left with murky water by the end so be sure to pay close attention when you’re adding the colouring or you might miss the wonderful effect!

What you will need:

A clean, clear jar
Room temperature water
Food colouring


1. Fill the glass with water (to about the three-quarter mark)

2. Add oil to the top, enough that you have a visible layer (the oil may initially sink in small balls, but it won’t mix with the water so wait for it to settle at the top of the glass).

3. Add food colouring – 2 or 3 drops of each colour works best.

4. Watch!

Water and oil in a jar, showing that they don't mix

When you have finished your fireworks in a jar experiment, it is really important that you check your local council website for disposal information. Most will advise you about getting rid of the mixture appropriately, always take care not to pour cooking oil down your sink where it may cause a blockage when it cools.

Enjoyed this post? Don’t miss our colour mixing fun with walking water.