mix in a ziploc baggie
place small baggie in a bigger ziploc bag filled with ice and salt
roll bags back and forth to freeze the ice creameat and enjoy!
If you’d like to try this, we used the recipe from Countertop Chemistry (which has a nice explanation of the science suitable for older children)..
1 large ziplock bag
|1 small ziplock bag|
|1/2 cup milk|
|1/2 cup cream|
|1/4 cup sugar|
|1/4 teaspoon vanilla flavoring|
Place milk, cream, sugar and vanilla in the small ziplock bag. Seal the bag and mix. Put 2 cups of ice into the large ziplock bag. Add 1/2 to 3/4 cup of salt to the ice. Place small ziplock bag inside the large bag. Close the large bag. Rock the large bag from side to side. Rock until the contents of the small bag have solidified - 10 to 15 minutes.
And I’ll add these tips to the recipe, I’ve found gently rolling the bag back and forth works better than rocking, but you need to protect your hands with a towel (see picture above). If you mix by rolling, you might want to double bag the ice-cream mixture before putting it in the larger bag to prevent holes and salty tasting ice-cream.
What will your child learn by doing this activity? For preschoolers, they will see that ice-cream can be made by cooling milk. For older children, you can explain that salt lowers the freezing point of ice helping to set the ice-cream.
If you want to investigate further, you could try making different flavours of ice-cream or compare the bag method to mixing the ingredients and putting them in the freezer.
This post was originally published in August 2009.