Ice Cream Ball – Play

Sick Science! Summer Camp - Make ice cream outside on hot summer days

Just when you thought making ice cream was old hat, someone comes out with a cool contraption that makes you work for your dessert. With the Play & Freeze Ice Cream Maker, there’s no need for electricity. Just add ice and rock salt in one end and ice cream mix in the other end–then have a ball as you shake it, pass it, or roll it. The ice cream mix can be as simple as cream, sugar, and vanilla, but the footwork on the ball is all you.

Experiment Materials

  • 1 pint of Half & Half*
  • 1 1/2 teaspoons vanilla
  • 1/3 cup + 2 Tablespoons sugar
  • Ice
  • Rock salt


  1. Fill the ice end with as much ice as possible and then add 1/2 cup of rock salt. (MEGA: Add 3/4 cup of rock salt).
  2. The lid should be hand tightened – do not use the wrench! Mix up your ice cream ingredients in a container, then pour the mix into the end with the metal cylinder, leaving about an inch for expansion at the top.
  3. Hand tighten the lid. Have a ball! Shake, roll, and pass it around as you mix and freeze the ingredients. It’s not necessary to shake the ball…just motion will do it!
  4. Don’t throw or kick the ball, because it is heavy and made from strong plastic. It will hurt if the plastic ball is winged across the yard at someone else. The kids in our experiment used an inflatable cover which made the ball easier to catch and less dangerous to fling around.
  5. After about 10 minutes (15 for the MEGA ball) open the ice cream end using the included plastic wrench.
  6. Scrape the sides of the cylinder to mix up the ice cream using a plastic or wooden spoon (don’t use a metal spoon as it will scratch the cylinder). Then check the ice end.
  7. Pour out the excess water and add more ice and up to 1/3 cup more rock salt to enhance the freezing ability. Close the lids securely and continue having a ball for approximately 5–10 more minutes. (15 for MEGA)

30 minutes total, including prep time and play time.

You now have about a pint (or quart for the MEGA ball) of delicious soft-serve ice cream. The consistency will vary based on the ice, your mix, the outside temperature, shaking frequency, etc. Once the ice cream is to the consistency of your liking, gently scoop it out, and enjoy!

How Does It Work?

What does the salt do? Just like we use salt on icy roads in the winter, salt mixed with ice in this case also causes the ice to melt. When salt comes into contact with ice, the freezing point of the ice is lowered. The lowering of the freezing point depends on the amount of salt added. The more salt added, the lower the temperature will be before the salt-water solution freezes. For example, water will normally freeze at 32 degrees F. A 10% salt solution freezes at 20 degrees F, and a 20% solution freezes at 2 degrees F. When salt is added to the ice, some of the ice melts because the freezing point is lowered.

Always remember that heat must be absorbed by the ice for it to melt. The heat that causes the melting comes from the surroundings (the warmer cream mixture). By lowering the temperature at which ice is frozen, you were able to create an environment in which the cream mixture could freeze at a temperature below 32 degrees F into ice cream.

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