Rainbow Foam!

Rainbow Foam!

Vinegar and Baking Soda- one of the oldest and greatest tricks in the book I would say! What makes it even better? Making rainbow foam with that reaction!!


  • Colour recognition and colour mixing
  • STEM activity (chemical reaction- bubbles, acids/bases, states of matter, colour mixing, counting scoops, measuring, etc…)


  • Vinegar (large container)
  • Baking soda (large or small one would do)
  • Liquid watercolour or food colouring
  • Bin or bathtub
  • Cups or jars for each colour you choose (clear would be best for viewing reaction)
  • Towels (to clean up if necessary)


1- Place jars in a bin or tub. You want one jar or glass per colour of your rainbow. Have all materials ready and easily accessible.

Rainbow Foam materials prepped and ready.

2- Scoop baking soda into cups. We filled about 1/4 of the way and it was a little too much. It did, however, allow us to keep adding vinegar to repeatedly create foam rainbows. This is a great step for child involvement. You can count scoops, teach measurement, etc…

Rainbow Foam Prep- Scooping baking soda into cups.

3- Add colour. We added liberally for vibrant coloured foam explosions. Liquid watercolour was approx. 2 tablespoons of colour and food colouring 10-12 drops. I get my liquid watercolour from Education Station. 

Rainbow Foam Prep- Colour added!

4- Have glasses of vinegar ready for each jar of ‘baking soda and colour’ for nicest rainbow foam effect. You could also pour straight from container. Another great step for child involvement.

5- Pour vinegar into baking soda and colour mix and watch the gorgeous rainbow foam reaction! Play with the rates at which the vinegar is poured. What happens when you pour slowly or quickly?

6- Repeat if you have excess baking soda in glasses to use up. Add more colour if needed.

Rainbow Foam Reaction!

7- I let my children get their hands dirty and play with the results. The final result was a deep purple bubbling potion that sparkled like diamonds on the surface. Colour easily washes out of clothing and the floor can be cleaned with a towel.


Talk about everything that is happening. Listen to the giggles and conversations. These are the coolest moments of experimenting. Those “oooohs” and “aaaahhs” and screeches of delight are irreplaceable.

Rainbow Foam!



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