Homemade Ice Cream (with a Side of Science)

Do you ever crave ice cream, but just don’t feel like suiting up for the grocery store? July is National Ice Cream Month, and you can make your own homemade ice cream at home this summer and all year long with only six ingredients and just 15 minutes! And bonus: you can call it science homework because this extra fast technique works with freezing point depression. 

Here’s what you’ll need: 

• 1 cup half and half 

• 2 tbsp. granulated sugar 

• ½ tsp. pure vanilla extract 

• 3 cups ice 

• 1/3 cup kosher salt 

• Your choice of toppings 

You’ll also need both a small and large resealable plastic bag. Start by putting the half and half, sugar, and vanilla into the small bag, press out any air, and seal. Put the ice and salt in the larger bag. 

How can this simple set-up make delicious vanilla ice cream in only 15 minutes? That’s where a little bit of science comes in. The magic ingredient is salt! Ice is always coated in a thin layer of water, and when salt is added to this “ice water,” it can drop the temperature from 32 degrees F (0 degrees Celsius) to –5.8 degrees F (-21 degrees Celsius). This is known as freezing point depression; the salted water doesn’t allow the ice to refreeze, but instead the water becomes colder—even when not in ice form. 

(Extra credit: When you add salt to boiling water, it actually increases the temperature!) 

Now that we know why the three ingredients in our small bag will freeze, put your sealed small bag into the larger bag alongside the ice and salt, seal the large bag, and prepare for a workout. You’ll need to shake your bag for up to 10 minutes. Bonus points if you rack up steps on your Fitbit or create a tune to the rhythm of your shaking! 

Once your ice cream is frozen, remove the small bag, open, and enjoy! You can add your favorite toppings, or you could even add other flavors to your bag before the freezing process. 

In addition to Ice Cream Month, July is chock full of flavor-related holidays. Be inspired by one of these ideas for a flavor or topping to try. 

July 1 – Creative Ice Cream Flavors Day (Mascarpone Lavender, anyone?) 

July 5 – National Apple Turnover Day (Who doesn’t want ice cream with that?) 

July 7 – National Strawberry Sundae Day (Bonus, it’s also Chocolate Day!) 

July 8 – National Blueberry Day 

July 17 – Peach Ice Cream Day 

July 19 – National Ice Cream Day 

July 20 – National Ice Cream Soda Day 

July 21 – National Junk Food Day (Some Oreo cookie crumbles and gummi bears, perhaps?) 

July 23 – Vanilla Ice Cream Day 

July 28 – National Milk Chocolate Day 

Now that’s a lot of celebrating a great use of freezing point depression! Share your ice cream concoctions in the comments. 🤤 🍨