A domestic ice cream maker is a machine used to make small quantities of ice cream for personal consumption. Ice cream makers may prepare the mixture by employing the hand-cranking method or by employing an electric motor. The resulting preparation is often chilled through either pre-cooling the machine or by employing a machine which freezes the mixture. An ice cream maker has to simultaneously freeze the mixture while churning it so as to aerate the mixture and keep the ice crystals small (less than 50 μm). As a result, most ice creams are ready to consume immediately. However, those containing alcohol must often be chilled further to attain a firm consistency. History Around 1832, Augustus Jackson achieved fame for creating multiple ice cream recipes and pioneering a superior ice cream preparation technique by adding salt to the ice. In 1843, Nancy M. (Donaldson) Johnson of Philadelphia received the first U.S. patent for a small-scale hand-cranked ice cream freezer. The ice cream freezer was a pewter cylinder. Dubbed the "Queen of Ices", Victorian English culinary entrepreneur Agnes Marshall was granted a patent for an ice cream machine that could freeze a pint of ice cream in five whole minutes. Process Ice cream makers may prepare the mixture by employing the hand-cranking method or by employing an electric motor. The resulting preparation is often chilled through either pre-cooling the machine or by employing a machine that freezes the mixture. An ice cream maker has to simultaneously freeze the mixture while churning it so as to aerate the mixture and keep the ice crystals small (less than 50 μm). As a result, most ice creams are ready to consume immediately. However, those containing alcohol must often be chilled further to attain a firm consistency. Some machines—such as certain lower-priced countertop models—require the resulting mixture to be frozen for additional time after churning is complete. Models Hand-cranked machines Nancy Johnson patented the first hand-cranked model in 1843. William Young produced the machine as the "Johnson Patent Ice-Cream Freezer" in 1848. Hand-cranked machines' ice and salt mixture must be replenished to make a new batch of ice cream. Usually, rock salt is used. The salt causes the ice to melt and lowers the temperature in the process, due to freezing point depression. The temperature at which salt water freezes is lower than the temperature at which fresh water freezes. The saltwater does not freeze and