Summer Science Lab: Make Ice Cream!

Did you know that ice cream has it’s own special part in history? It’s true! The Chinese were the first to develop ice cream, somewhere around 3000 BC. Roman emperor, Nero, was fascinated with the stuff, and is credited as the first person on record to have ice cream made for a meal. Marco Polo introduced Italy to ice cream, and the trend spread rapidly across Europe. Dolly Madison served it in the White House, and waffle cones were first introduced at the St. Louis World’s Fair in 1904. (The vendor ran out of bowls, and improvised with rolled up waffles, much to our luck.)

You can make your own ice cream at home with a few ingredients and a little bit of science know-how. You don’t even need any fancy equipment. Why not give it a try this summer?

You’ll Need:

• 1 gallon jar (plastic is best for safety reasons)
• crushed ice
• rock salt
• 2 zip-lock bags
• half and half
• sugar
• vanilla extract
• gloves

1. Fill your container halfway full with crushed ice.

2. Add 6 tablespoons of rock salt.

3. Seal jar and shake for 5 minutes. You will want to wear gloves – the jar gets very cold!

4. In a zip-lock bag, mix:

• ½ cup half and half
• 1 tablespoon sugar
• ½ teaspoon vanilla extract

Get as much air out of the bag as you can, and seal it tightly. (Air can make the bag pop during the freezing process.)

5. Put the zip-lock bag into a second bag to help avoid spillage. Again, press out as much air as possible and seal the second bag.

6. Place the double-bagged mixture into your jar with the ice and salt. Close the container tightly.

7. Put on your gloves. Get ready to shake! You can shake and roll the container, or mix however you’d like. You may want to wrap it in a towel if it gets too cold to handle. You will need to do this for about 20 minutes, so get a friend or parent to help out if needed.

8. That’s it! You’ve got ice cream! If your ice cream isn’t as firm as you’d like, shake a little longer.

9. Remove bags from the container and rinse with cold water. You don’t want to eat any salt on the outside of the bag.

10. Store any leftover ice cream in a freezer, of course.

11. If you want to try making it again, you can experiment with a different flavor or stir-in, like chocolate chips or candy pieces.

Why Does It Work?

Salt causes the ice to melt. But, as they mix together, the freezing point of the ice is lowered. By lowering the temperature at which ice can freeze, you create an ideal environment where the cream mixture inside the bag freezes as well. The shaking and rolling motion makes the warm pockets in the mixture move to the outside of the bag, making a nice even freeze with a smooth texture.

Yummy science!