Rainbow Oobleck: A Colourful Sensory Activity

Rainbow oobleck makes playing with regular oobleck, also known as magic mud, even more fun! This bright and colourful sensory activity is engaging and easy to clean up!

You’ve probably heard of oobleck, magic mud, or goop, or another name this mysterious substance goes by. Either way, mixing cornstarch and water provides a little magic for children of all ages.

Oobleck is so much fun for children, because of its magical property. If you touch it, it gets hard, but if you keep still, magic mud will melt off your hand.

Oobleck is a class activity for us in part because it’s so much fun, but also because it’s so darn easy to clean up! It never stains. Simply sweep up any crumbs, then wipe the surface down with a wet cloth and you’re done!

Oobleck is formed when you mix cornstarch and water. I usually start by mixing in equal parts, then adding more of either ingredient until I acheive the consistency I want.

My kids love any kind of oobleck, but rainbow oobleck really takes it up a notch. It’s so beautiful to look at, even though the rainbow only lasts a few minutes, until it’s all mixed together.

Although it looks complicated, rainbow oobleck was so simple to make and took only a few minutes.

Raibow oobleck

How to Make Oobleck Without Flour

This is a common misconception about oobleck. You actually do not need flour at all to make any kind of oobleck. In fact, substituting flour for cornstarch will create a paste, like the kind you use for paper mache, not oobleck at all!

Taste-Safe Oobleck

Rainbow oobleck, or any oobleck for that matter, is perfectly safe for babies and toddlers to play with. Because the two ingredients that make oobleck at water and cornstarch, babies will be able to taste it with no problems. Be sure to use food colouring rather than liquid water colours if you have a baby or mouthing toddler. baby playing with rainbow oobleck

How to Make Rainbow Oobleck

So without further ado, here are the materials and instructions for rainbow oobleck.

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Materials for Rainbow Oobleck


  • toys/tools to play with (spoons, cookie cutters, etc.)
  • towels for easy clean up

easy clean up for rainbow oobleck

Instructions for Rainbow Oobleck

  • Add an equal amount of water to each bowl (the amount will be dependent on how much oobleck you want to make, but 1/4 cup is a good amount to start).
  • Mix food colouring into the water (each bowl should be a different colour of the rainbow)
  • Add the same amount of cornstarch to each bowl.
  • Stir until cornstarch is mixed in, adding more or either ingredient if the consistency is not quite right (should be hard when you touch it, but runny when you hold it with your hand open)
  • Add each colour to your larger container, working from one side to the other. Be prepared to do this quickly before the colours spread out.
  • Throw some towels down for extra easy clean up.
  • Let your kids at it and enjoy!

If you like this activity, try our other bright and colourful activities here:

Rainbow Toast: A Fun Breakfast Activity

Coloured Ice Cube Surprise: A Baking Soda and Vinegar Experiment

Ice Painting: An Outdoor Fine Motor Activity

Awesome Frozen Paint Art Activity


I hope you and your families enjoy these activities as much as mine did!

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Author: Cindy

Cindy is an kindergarten teacher and former district Literacy Lead who feels passionately about play-based learning. Cindy has a Master's Degree in Education, with a focus on Curriculum Studies. She is the mom of two sweet girls and a big old doggy. In between playtimes, she enjoys chai tea and a good book.

7 thoughts on “Rainbow Oobleck: A Colourful Sensory Activity”

  1. Quick question. So 1/2 cup corn starch to 1/4 cup water or vice versa. Want to do this activity with my toddler class. How would you this for a toddler class with 8 kids.

    1. That’s correct.

      I think your toddler class will have a ball. You could certainly do this with all 8, or have them come to you 2-4 at a time, with the others doing another activity with another adult. There will obviously be some clean-up involved, but it is such an engaging activity. Good luck!

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