How to make a rain cloud in a jar

This simple visual activity is great for understanding why rain falls and how clouds form.

Children can experiment with different sizes and shapes of shaving foam clouds and watch how it affects how the food colouring rain falls.

glass full of water with a layer of shaving foam over the top. Food colouring is dripping through the shaving foam to the bottom of the jar.

What is a cloud?

Clouds are droplets of water and crystals of ice. The exact composition depends on the temperature. Clouds form when warm air rises, expands and cools. Water molecules then attach to dust, pollution and smoke particles. When these molecules come together, they form a cloud. Clouds float because the water droplets forming them are warmed up by the heat from the sun, and warm air rises.

The altitude at which clouds form depends on several factors, such as air temperature, wind and size of the cloud.

How to make a rain cloud in a jar

You’ll need

A jar

Shaving Cream

Water

Food colouring

Dropper or pipette

Rain cloud in a jar instructions

Fill the jar about ¾ full with water

Cover with shaving cream to completely cover the surface of the water. The shaving foam represents a cloud.

Drip water over the shaving foam using a pipette

Drop food colouring over the shaving foam.

Watch the food colouring fall to the bottom of the jar.

How does a rain cloud in a jar work?

Clouds form when water vapour rises and cools back into water droplets to form clouds.

When a rain cloud reaches a certain mass, the water needs to escape and so breaks through the cloud to fall as rain. As you drip the water over the shaving cream cloud, the water starts to fall through the cloud.

Our rain cloud in a jar is a very simple model of how rain forms, but it is a lot of fun to set up and watch!

Why are rain clouds grey?

When clouds become full of water droplets, they are so thick that light cannot travel through them, making the cloud look grey! This is why grey clouds are a sign that rain is about to fall.