How to make a rain cloud

Carefully add a layer of shaving cream to the water.
The shaving cream represents a cloud and the water is the atmosphere. 

Simply add a few drops of blue food colouring to the shaving cream. The weight of the food colouring will start to push through the shaving cream and fall down through the water; (the darker grey clouds were heavy with water droplets or rain, the food colouring.

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