Ice Cream Maker
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An ice cream maker or ice cream freezer is a machine used to make homemade ice cream. There are both manual and electric types of machine.

An ice cream maker has to do two things; the mixture has to be cooled, and during this cooling process, the mixture has to be constantly churned to break up ice crystals that form and introduce some air to the mixture so that the resultant ice cream will have a smooth, creamy texture. Whatever the type of ice cream maker, it is possible to make ice cream of a texture that is ready to serve straight out of the machine. However, some recipes, especially those containing alcohol, need to have the freezing process completed in a freezer before the ice cream is a firm enough consistency. Once ice cream is in the freezer, it usually needs to be taken out of the freezer between 20 and 30 minutes before serving to soften it, partly to make it easier to serve and eat and partly because when ice cream is very cold, the flavour is impaired.

Some machines, such as certain low-priced counter-top models, require that the resulting mixture be frozen an extra four hours or more (or overnight), depending on the recipe, in order for the ice cream to harden to a desired consistency.

Manual Machines

These machines take the form of an inner bowl which sits in a larger outer bowl. The inner bowl has a handcranked mechanism which turns a paddle (sometimes called a dasher) to stir the mixture. The outer bowl is then filled with a mixture of salt and ice which provides the cooling power. The addition of salt to the ice causes freezing-point depression. As the salt melts the ice, its heat of fusion allows it to absorb heat from the ice cream mixture, freezing the ice cream.

This type of ice cream maker is inexpensive, but inconvenient and messy as during the process the ice and salt mixture melts and then the user is left with a lot of salty water to dispose of. Also, between each batch of ice cream the ice and salt mixture has to be refilled.

There are also very small manual models which are pint-sized bowls whose walls are filled with a coolant. The paddle is normally combined with a plastic top. The mixture is poured into the frozen bowl and placed in a freezer. The paddles then are turned by hand every ten minutes or so for a few hours until the desired consistency is reached.

Electric Machines

There are three types of electric ice cream machine. Each has an electric motor which drives either the bowl or the paddle to stir the mixture. The major difference between the three is in how the cooling is performed.

Counter-top machines use a double-walled bowl which contains coolant between the two walls. This is frozen in a domestic freezer for up to 24 hours before the machine is needed. Once frozen, the bowl is put into the machine, the mixture is added and the machine is switched on. The bowl spins, which stirs the mixture over a stationary paddle assembly. Twenty to thirty minutes later, the ice cream is ready. The advantage of this type of electric machine is low cost, typically under $100. The disadvantage of the pre-frozen bowl approach is that only one batch can be made at a time. To make another batch, the bowl must be frozen again. For this reason, it is usually possible to buy extra bowls for the machine, but of course these take up a lot of freezer space.

Small freezer-unit machines sit inside of the freezer section of a refrigerator and operate similar to a food processor in slow-motion. The paddles turn every few seconds to stir the mixture enough so that large ice crystals do not form. Some of these machines require that the electrical cord be plugged in outside of the freezer, which can be cumbersome. Some refrigerators made after 1982 have a built-in ice-cream maker as an accessory or a specialized electrical plug for use with certain freezer-unit machines. The advantage of this approach is that no pre-freezing of the appliance is necessary. However, some people feel that this type of machine produces a lower-quality ice cream because of its slow-motion method.

More expensive machines dispense with the coolant bowl and instead have their own mini-freezer built in. When using these machines, the cooling system is switched on about 5 minutes before the machine is needed, and then the mixture can be added and the paddle switched on. As with coolant-bowl machines, ice cream is ready in 20 to 30 minutes. The huge advantage of this approach is that use of the machine requires no pre-planning, and batch after batch of ice cream can be made. The main disadvantages are cost, as these machines cost upwards of $300, and size. As well as being large, these machines usually cannot be moved without waiting 12 hours to use the machine again as moving the unit upsets the coolant in their freezing system. For this reason, it is normal to keep these machines permanently on the work surface, which can be impractical in a smaller kitchen. Because of these disadvantages, these machines are usually only for ice cream fanatics.