Ice cream has been around for a couple of centuries, at first it was mostly reserved for the elite because it was difficult to make. In the summer months, when a frozen dessert was desired, the supply of ice was limited. The ice had to be collected in the winter and stored in an ice house, usually packed in sawdust to keep the blocks from freezing.
Ice and rock salt were added to the bucket in layers. The salt lowered the melting temperature of the ice, causing the cylinder filled with cream and other ingredients to cool below the freezing point of the cream. The handle had to be continuously turned to prevent the mixture from freezing and to create a creamy texture. For more information you can also go to bondiicecreamco.com/.
This method of making ice cream is still used today and is the first type of frozen dessert maker I will discuss. Today's automatic version replaces the hand crank with an electric motor that does the hard work of continuously stirring the cream mixture. Of course, you can still buy the hand crank models and making ice cream by hand can be a fun activity on a hot summer day.
The following type of automatic ice cream maker does not use ice or salt to obtain a freezing temperature. Instead, they use a special double-walled container (also known as a cylinder, tub, or bowl). This container is filled with freezer gel; similar to reusable gel packs for freezing. The gel freezes and melts slowly, allowing you to keep things cold for a while.
When it's time to make the frozen dessert, the frozen container is placed in the ice cream maker, ingredients (pre-chilled) are added, a whisk is inserted, and the motor mixes the cream as it begins to freeze. These machines can also be used to make frozen yogurt, sherbet, sundaes, and even frozen drinks like margaritas.
The third type of automatic refrigerators are those that have a built-in compressor that acts as a mini freezer. To use you turn it on and add the ingredients. The machine maintains the correct temperature and continuously mixes the ice cream.
These models are more expensive than the gel freezer models, costing in the $200 range and up. The advantage of these is that you can make multiple batches of frozen desserts in a single day without needing to freeze multiple bowls of freezer gel.