Explore Valentine’s Day science with a fun candy heart oobleck activity. Once you learn how to make oobleck, you won’t be able to stop! Not only is homemade oobleck an awesome science project to explore non-Newtonian fluids (read more about that below), it’s an incredible sensory play recipe for kids who really love to dig in and explore with their sense of touch.

Candy Hearts Oobleck Science Activity

Candy heart oobleck activity for easy Valentine's Day Science, STEM, and sensory play!


You will want to raid your kitchen cupboards for this one! Making candy heart oobleck is as simple as grabbing two household staples, water and cornstarch and mixing them up! However, it’s the ratio of water to cornstarch that is so important in this oobleck recipe.

Make sure to check out more awesome kitchen science experiments!


Oobleck is a fun substance made from a mixture of cornstarch and water. It’s a bit messy too!

It’s also a non-Newtonian fluid. Although it doesn’t feel like our traditional slime recipe like our Valentine Slime, it has many of the same properties.

These properties or characteristics make it a great chemistry experiment that also explores states of matter, mixtures, and substances.

A mixture is a material made up of two or more substances to form a new material which is our oobleck! Here we are combining a liquid and a solid, but the mixture doesn’t become one or the other.

A solid has its own shape whereas a liquid will take the shape of the container it is put into. Oobleck is a bit of both!

That’s why oobleck is called a non-Newtonian fluid. This means it is neither a liquid nor a solid but a bit of both! You can pick up a clump of the substance like a solid and then watch it ooze back into the bowl like a liquid.

Touch the surface lightly and it will feel firm and solid. If you apply more pressure,  your fingers will sink into it like a liquid.

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Open the cupboards and get set for a fun candy heart activity


  • Candy Conversation hearts
  • 1 Cup Cornstarch
  • 1-1.5 Cups of Water
  • Bowl
  • Spoon
  • Food Coloring (optional)
  • Shallow Pan or Pie Dish

We also added a spoon, tweezers, cookie cutters, and heart-shaped containers.

Note: We first set this oobleck activity up in 2015 and it’s still a favorite. See some of our older photos below.


There’s no way around the messy side of this candy heart oobleck science activity, so be prepared and embrace the mess while the kids enjoy a cool learning experience. You can contain the mess with disposable table clothes or show curtains or take it outside if you have nice weather.

I would suggest putting the oobleck in the trash when finished. Although it does wash down the sink easily, it’s a lot of goop for the pipes to handle.


Step 1: Start by adding the cornstarch to the bowl.

I always recommend having extra cornstarch on hand for experimentation with ratios or if the kids accidentally add too much water. Oobleck is very forgiving! You will just end up with a larger amount in the end!

You can easily add food coloring to the water first. Remember for a bold color as you see here, you will need extra food coloring. For an artistic approach to adding color, see our marbled oobleck activity! You can add the color after instead.

However, food coloring is not necessary and you will see with the candy hearts, they add their own color! We were able to throw in a little extra science with dissolving candy hearts experiment too.

Step 2: Add the water and get ready to mix. You should start with 1 cup of water first and then add as needed.

The good thing about this classic heart oobleck recipe is that if you add to much water, you can add more cornstarch.

If you add too much cornstarch, go ahead and add back in some water. I highly suggest making small changes at a time. A little can go a long way once you start incorporating it into the mixture.

You can start by mixing your oobleck in a bowl and then transfer to a more shallow tray to allow for a larger play surface if desired!


There is a gray area for the right oobleck consistency. First, you don’t want it to be very crumbly, but you also don’t want it to be very soupy either. If you have reluctant kiddo, hand them a spoon to start! Let them warm up to the idea of this squishy substance. Never force them to touch it though.

The perfect consistency is when you can pick up a clump in your hand, form it into a ball of sorts, and then watch it flow like a liquid back into the pan or bowl.

Once you have your oobleck mixed to the desired consistency, you can add your candy hearts and other accessories as desired! Check out the little hands exploring the candy heart oobleck below.

Candy Hearts Oobleck science sensory play set up cornstarch water activity


Candy Hearts oobleck science messy sensory play


Want to experiment with viscosity? Viscosity is the physical property of fluids and how thick or thin they are including how they flow. Why not learn about viscosity by changing the ratio of water to cornstarch.

You could even try to make oobleck with flour, powder, or baking soda and compare the similarities and differences.

We have also made this cornstarch slime with just glue and cornstarch.

Mix up easy Valentine’s Day science with candy heart oobleck!

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