Kids of all ages enjoy making ice cream in a bag. It's a fun activity that's also educational since it demonstrates the interaction of salt and ice as it lowers the freezing temperature of the sweetened cream mixture.
We learn how our forebears made their own homemade ice creams when nowadays it's something that's normally store-bought. But, best of all, making freezer bag ice cream is simply loads of fun for anyone.
©2004 by Don Bell
This easy recipe can be used to entertain the kids on a rainy day, or to simply offer a fun activity and treat with friends. It's one student science project you can't resist trying.
After all, the frozen ice cream always turns out delicious!
To make ice cream in a bag, here's what you'll need for each serving: 2 quart-size Ziploc® freezer bags and 1 gallon-size Ziploc® freezer bag.
Freezer bags work better than sandwich bags for making ice cream because they are thicker and will take a lot more abuse. Any brand can be used, but the bags must be tightly sealable.
Mitts or gloves are also required because the mixture grows noticeably colder as the salt melts the ice surrounding the inner bag.
Now, let's make some ice cream!
The ice cream in a bag recipe makes a great student science project to demonstrate the old fashioned ice cream making process. It's also perfect for a tasty show and tell classroom presentation.
Your hands can feel the mixture growing noticeably colder as the salt melts the ice surrounding the inner bags. What happens is the brine solution absorbs the heat from the mixture and allows it to begin to freeze.
If there were no salt added to the ice, it would melt at 32°F (0°C), the melting point for freshwater ice, which is not cold enough to make freezer bag ice cream.
Salt speeds the melting of the ice and lowers the temperature to the melting point of saltwater ice, approximately 29°F (-2°C), depending on the saltiness of the water. The lower melting temperature is necessary for the mixture to freeze.
The same freezing principle is involved when making old fashioned coffee can ice cream, a more traditional version of bag ice cream.