Touch the Rainbow

Sensory Science Rainbow Oobleck

Touch the Rainbow: Sensory Science Rainbow Oobleck

Discovery Place Science

Won’t look like rain. Won’t look like snow. Won’t look like fog. That’s all we know. We just can’t tell you any more. We’ve never made oobleck before.” — Dr. Seuss, “Bartholomew and the Oobleck”

Have you ever made oobleck before? Inspired by Dr. Seuss’s book, “Bartholomew and the Oobleck,” this mysterious substance is as difficult to describe as it is to grasp. Rainbow oobleck, also known as magic mud, is one of the coolest and easiest sensory science experiments for kids of all ages.

Oobleck Science

Playful experimentation with oobleck is a great way to explore the properties of liquids and solids, known as states of matter. A solid maintains its own shape, whereas a liquid will take the shape of its container.

Oobleck is made by combining a solid and liquid, but the resulting mixture doesn’t become one or the other. Oobleck is a bit of both states of matter!

Oobleck is an example of a non-Newtonian fluid, a substance that acts like both solid and liquid. You can pick up solid clumps of oobleck and then watch it drip through your fingers and ooze back into the bowl like a liquid. Touch the surface lightly and it will feel firm and solid, but with more pressure your fingers will sink into it like a liquid.

This apparent magic occurs because non-Newtonian liquids demonstrate variable viscosity, which means the fluid “thickness” and flow may change as force is applied or time elapses. Newtonian liquids such as water have constant viscosity.

Let’s Make Oobleck

Easy to make and great for hours of hands-on, playful learning, you will be amazed by what this part-liquid, part-solid can do! So, head to the kitchen and prepare to get a little messy.

Learning Time: 20 – 40 minutes

Prep Time: 5 minutes

Age Range: Preschool – Elementary

Materials List:

  • Water
  • Cornstarch
  • Food coloring or liquid watercolors*
  • Mixing bowls (or cups) and utensils
  • Large container, bin or tray
  • Measuring cups (optional)
  • Glitter, beads or small toys (optional)

Preparation:

  1. Collect and arrange oobleck materials. Six bowls or cups are required for standard rainbow oobleck, but you can make as many or few colors as desired.
  2. Rainbow oobleck is non-toxic and completely safe for babies and toddlers to play with and even taste when dyed with food coloring. Be sure to use food coloring rather than liquid watercolors if you have young children. Older kids and adults can experiment with liquid watercolors to create more vibrant rainbow oobleck in brighter hues.
Oobleck 1

Directions:

  1. Measure and pour equal amounts of water into each bowl. The water amount depends on how much oobleck you want to make, but 1/4 cup water per bowl is a good starting amount.
  2. Mix food coloring (or liquid watercolor) into water, so each bowl is dyed a different color of the rainbow. Dye water desired color knowing that oobleck will be lighter (more pastel) after adding the cornstarch. If you prefer more vibrant colors, quite a bit of coloring (ideally liquid watercolor) is needed.
  3. (Optional) This is a great opportunity to teach kids about color theory and mixing. Before adding dye, ask which colors would make green, orange and purple. Work together to experiment and select dye combinations before mixing each color.
  4. Work cornstarch between your fingers to eliminate all clumps before adding equal parts cornstarch to each water bowl. While there is not an exact ratio of water to cornstarch, the general guideline is to try 1 cup of water for every 1-2 cups of cornstarch. If the mixture is too runny, add cornstarch. If it's too thick, add water. Oobleck is the correct consistency when you can form clumps into solid balls that melt like liquid back into the bowl when you open your hand.
  5. Combine colors to create rainbow oobleck by adding each color to your larger container, pouring from one side to the other. Be prepared to do this quickly before the colors spread out.
  6. (Optional) Add glitter, beads or small toys to add texture and explore how oobleck interacts with solid objects.
Oobleck 2

Even More Oobleck

There are endless ways you can play with oobleck. It is perfect for experimentation – trying different things, observing what happens and figuring out why it works that way. Here are a few ideas to extend your oobleck sensory exploration and experimentation.

  1. Fill a cup or bowl with oobleck, quickly flip it upside down and observe what happens. Oobleck should stay in the upside-down cup until force is applied, which breaks the colloid tension.
  2. Pour oobleck into a strainer or colander and observe it slowly drizzle out. Does the drip remain constant, slow down or stop? What happens if you stir the oobleck?
  3. Tap the oobleck mixture. Does it act like water and splash? Or is it more like a solid, firmly maintaining its shape against your hand? What happens if you hit it harder?
  4. Try cutting and lifting a “slice” of oobleck. What happens and why?
  5. Can you make oobleck with flour, powder or baking soda instead of cornstarch? This is a great way to experiment with different mixtures, make comparisons and draw conclusions! (Hint: Substituting flour for cornstarch will create a paste, like for papier mache, not oobleck at all).
  6. Compare oobleck to other non-Newtonian liquids such as ketchup or syrup. Do all non-Newtonian liquids demonstrate the same variable viscosity? (Hint: While oobleck becomes harder the more you play with it, ketchup becomes runnier the more you shake it).
Oobleck 3