Generally speaking, there are two basic styles of ice-cream maker — manual and electric. They can be simple or fancy and can cost from $25 to almost $1,000. In addition to ice cream, they can be used to make ice milk, frozen yogurt and frozen drinks. All of them work on the same principle — a canister with a central, vertical paddle (called a dasher) is placed inside a container that holds the freezing agent — either ice and salt, a chemical coolant or an electric refrigeration unit. The inner canister is filled with an ice-cream mixture that the dasher stirs (gently scraping the sides of the canister) when rotated. This stirring action aerates the mixture and keeps it smooth by preventing ice crystals from forming while it freezes. There are several different kinds of ice-cream freezers. Among the manual-style ice-cream makers are the old-fashioned, wooden buckets with a metal inner container for the ice-cream mixture. They require ice, rock salt (which lowers the temperature of the ice) and plenty of physical stamina to turn the crank that rotates the dasher. They usually take 30 to 40 minutes to make 4 to 6 quarts of ice cream. Some of these wooden bucket-style makers have an electric motor that sits on top of the unit, saving manpower. A newer form of manual ice-cream maker is the prechilled chamber freezer, which ranges in size from 1 pint to 1 1/2 quarts. The container is placed in the freezer for 24 to 48 hours to freeze the coolant sealed between the walls lining this unit. The ice-cream mixture is poured into the center cavity; a crank-and-dasher assembly and lid covers the entire unit. The hand-rotated crank is turned once every 2 to 3 minutes for 15 to 30 minutes, depending on the amount of ice cream being made. Electric ice-cream machines are all equipped with electric motors that rotate either the ice-cream canister or the dasher. There are several different styles and sizes of electric ice-cream machines. The most common is the self-contained countertop unit that uses refrigerator ice cubes and table salt, and in which the motor turns the canister. This type can make up to 2 quarts of ice cream. There is also a small freezer unit (averaging 1 quart) that doesn't require salt or ice but instead is placed in the freezer compartment of the refrigerator with the electric cord exiting between the freezer's seal and the closed door. In this type, the dasher is motor-turned, while the canister is stationary. The Rolls-Royce of electric ice-cream freezers is the large, self-contained countertop machine that has the freezing unit built into it. All that's required for this expensive pleaser is to pour the ice-cream mixture into the canister and flick a button.