Fun Science: Rainbow in a jar

Everyone loves rainbows. Even on a wet and miserable rainy day with a bit of sunshine a rainbow can easily brighten up your day and put you in a good mood. This experiment allows you to create your own rainbow jar using simple household ingredients.

You will need:

St. Patrick's Day Science Experiment for Kids: Rainbow Jar.

You will need…

  • a tall, see-through container,
  • honey
  • golden syrup
  • washing up liquid (blue or green)
  • olive oil
  • water
  • food colouring




  • Add the honey to the jar. It may be easier to use a squeezy bottle as this will create less mess. This will also prevent it from touching the sides, ensuring the experiment works well.
  • Add the golden syrup you may want to mix it with food colouring first so that it stands out from the honey. This will help to create the rainbow. Try not to touch the sides of the jar and place the syrup in the middle, on top of the honey layer.
  • Then add the washing up liquid to the jar.
  • Now you need to add colouring to the water (any colour is fine as long as it stands out against the washing up liquid. Then add the coloured water to the jar.
  • Next you will need to add the olive oil to the jar. This needs to be the thickest layer.


Fun kids' science experiment. Make a rainbow in a jar. {Playdough to Plato}

Photo from Playdough to Plato

The Science Bit:

So what keeps all these layers all separated from each other? It’s how dense, or heavy, each liquid is. The golden syrup is heaviest, and sits nicely on the bottom. The washing up liquid is not quite as dense as the golden syrup, but it’s heavier than the olive oil, and so on.

Layering them from heaviest to lightest from the bottom to the top ensures that the rainbow maintains its distinct lines.

What if you had added the layers in the reverse order? Would you still see a rainbow? Try it.

What if you changed the colours around but added each liquid in the original order?

What happens if you mix your rainbow with a spoon?