Fireworks In A Jar!

JoFamily Life, Science Fun

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

I’ve mentioned previously our love of science, so one thing we just love to do on 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) is a simple science experiment. You may have seen our colour mixing fun (if not you can catch up here). Another mixing (or not in this case) experiment is this one: fireworks in a jar.

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

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, as it is interesting to see the oil and water stay separate. The food colouring is heavier than the oil and the water, so will ‘fall through’ the oil layer in small drips, creating the firework type effect in the water as it falls down to the bottom of the jar. If you use water based food colouring then the colour and the water will mix however. 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!

N.B. Please look at your local council website for information on disposing of the liquid mix, being especially mindful not to pour cooking oil down your sink!