Rainbow Burst Oobleck

Ever since the twins were very small, the simple combination of cornstarch and water has never failed to fascinate them. If you haven’t played with oobleck (otherwise known as “goop” or “cornstarch slime”), you are in for a treat- as a non-Newtonian fluid, oobleck acts like a liquid one moment and a solid the next. As the twins have gotten older (they are 3.5 now), their interest in this substance has shifted from purely sensory to more scientific as they ask questions and make observations about the strange behavior of the gooey stuff.  Today we were stuck indoors due to a nasty storm, so I thought I’d add a twist to our typical oobleck play- we added one new ingredient that made our goop explode with rainbow bursts of color. And oh, was it ever awesome.

Rainbow Burst Oobleck- Twodaloo

Rainbow Burst Oobleck

The other cool thing about this particular variety of oobleck is it looks JUST like fireworks when you first make it! So if you are incorporating patriotic activities into your play OR you just need something to occupy the kids during an epic backyard barbecue, here’s your answer.

Rainbow Burst Oobleck- Twodaloo

Isn’t it gorgeous? Almost too pretty to touch…almost.

Rainbow Burst Oobleck- Twodaloo

Once the twins dove in and started playing with the mixture, you can see that it turned into the most bubbly, swirly, colorful, AMAZING tray of oobleck you’ve ever seen. Don’t you want to just dive in and play with them?

Rainbow Burst Oobleck- Twodaloo

Seriously. It’s like playing in a painting. A bubbling, bursting painting.

Rainbow Burst Oobleck- Twodaloo

Ok, are you sufficiently curious? Ready to see how to make your own rainbow burst oobleck?

Rainbow Burst Oobleck Recipe

You will need:

  • Cornstarch (cornflour in the U.K.)
  • Water
  • Fizzy Bath Tablets (available at grocery stores in the bath aisle or click HERE to see the ones I use on Amazon)

First, find a container for your oobleck. We used a large glass pan. Next, add your fizzy tablets. I used scissors to cut each tablet into four smaller pieces (they were really easy to break up) to make them stretch further, but you could leave them whole, too. The twins arranged them in the pan, and we talked a bit about what we thought might happen when we added our oobleck based on what we know happens when these tablets are dropped in the water.

Rainbow Burst Oobleck- Twodaloo

Next, the twins helped me mix a box (plus a little more) of cornstarch with plain tap water in a separate bowl. I didn’t measure, we just added a little at a time and incorporated it with our hands until the oobleck was the consistency of thick honey. Then we poured it on top of the bath tablets and watched the magic happen!

Rainbow Burst Oobleck- Twodaloo

It only took a few seconds for the tablets to activate and begin releasing color and bubbles, which rose to the surface of the oobleck in bright bursts. You can see how they looked in the first two photos in the post before the twins dove in- just like fireworks! As the twins and I mixed and manipulated the oobleck, the tablets continued to bubble and release swirls of color, so the oobleck never lost its beautiful swirly appearance, even though the base color became a grayish purple instead of white. Can you see the bubbles among the swirls of color in the photo above? So pretty and engaging! We love these fizzy tablets for play and learning- you get a ton of them in the jar so you get a lot of bang for your buck. We also used them for our Color Tubs which is one of our favorite toddler activities.

Rainbow Burst Oobleck- Twodaloo

It was so fun to watch the twins explore the physical properties of the oobleck along with the swirls of color and bursts of bubbles. They dripped the oobleck from one hand to the other and let it ooze through their fingers.

Rainbow Burst Oobleck- Twodaloo

They noticed that their hands would sink into the oobleck but that it was difficult to pull them back out quickly- they found this fact quite fascinating. They also loved that they could slap the oobleck and it wouldn’t splash, and that they could run their hands across the top as if it were a solid surface.

Rainbow Burst Oobleck- Twodaloo

Pretty soon they incorporated some of their kitchen toys, and remarked on how hard it was to get their “rainbow pudding” out of the bowls once they scooped it in.

Rainbow Burst Oobleck- Twodaloo

They also found it very interesting that their toy whisk simply bounced off the surface of the oobleck rather than sinking in when they tried to use it to mix.

Rainbow Burst Oobleck- Twodaloo

All in all, it was a success! This activity engaged the twins on multiple levels and was a great introduction to the discussion of states of matter as the oobleck behaved like both a solid and a liquid, and the fizzy bath tablets produced gas that could be observed as bubbles forming in the oobleck.  Both of my kids spent the rest of the day commenting on all the things in our house that were solids or liquids, which I always love to see! Although the fizzy bath tablets are meant for coloring bath water and not skin, we did see some temporary staining from handling them in such a concentrated form, but the stains were gone after bath time the same day. We wore play clothes  to be on the safe side, but the color washed right out (we threw them in the wash right after playtime). Cornstarch oobleck is safe for little ones who mouth (although not tasty), but please supervise closely or skip the fizzy tablets if your little one is still tasting sensory materials, as the color tablets are not edible.

Rainbow Burst Oobleck- Twodaloo

Developmental Skills

This activity is a fun form of sensory play, which is great for all areas of development. Here are some of my most popular posts on the benefits of sensory play- be sure to check them out!

Our rainbow burst oobleck also stimulates cognitive development as the children observe the different ways the oobleck behaves (i.e. when poured vs. when squeezed) and draw conclusions about how it will move in new situations. The twins testing the whisk in the oobleck is a perfect example of learning through hands-on play experiences. The activity also provided a chance to learn about color mixing as the twins observed what happened as the different colors overlapped and swirled together.

More Great Stuff For You!

If you liked our Rainbow Burst Oobleck, you might like our fun Galaxy Slime sensory play activity.

Galaxy Slime- Twodaloo

Or, click HERE to view our entire sensory play gallery- lots of great stuff there, too!

Sensory Play Gallery- Twodaloo

Rainbow Burst Oobleck at Twodaloo


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  1. Have you thought about trying this with Pop Rocks or Fizzies candies instead of the bath tablets? That might give a way for the tasters to still play in color.

  2. Stephanie says:

    Hi Connie!
    I have seen Pop Rocks done on other blogs but the experience appears to be different- the color isn’t as vibrant or long-lasting and although the candy makes a popping sound (which I think is probably super fun!), it doesn’t give off bubbles or create the “blooming” effect that the color tablets do. I have no idea about Fizzies candy, though. Let me know if you try it!

  3. Wow! I love this.


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