Frozen carbonated drink

The FCB machine was invented by Omar Knedlik, then the owner of a Dairy Queen franchise. In the late 1950s, his restaurant lacked a soda fountain. Instead, he stored soda in his freezer. His customers loved the slushy drinks, so Knedlik tried to capture them with a machine. By the mid 1960s, about 300 machines had been manufactured. In 1965 7-Eleven licensed the machine, and began selling the Slurpee.

The back-end of an FCB machine is very similar to a regular soda fountain. Concentrated flavor syrups are mixed with filtered water, then carbonated. This mixture is then injected into a cylinder surrounded by freezer coils. The mixture freezes to the wall of the cylinder, then is scraped off by a rotating dasher, which also keeps the mixture uniformly mixed. FCB machines will often freeze to a temperature well below the freezing point of water, but the combination of pressure (up to 40 p.s.i.), sugar, the carbon dioxide mixture (carbonic acid freezes at -80 °C[1]), and the constant stirring prevent the mass from freezing solid.

FCB machines are distinctive from other slush drink machines in that they require a pressure chamber and a carbon dioxide source. Many modern non-carbonated slush machines use a spiral-shaped plastic dasher to scrape crystals off a freezing cylinder, often integrated into a clear hopper. This product is often much 'wetter' than a true FCB. On the other hand, non-carbonated machines are much simpler and less expensive, and so they are more common. A non-carbonated slush machine can be purchased for well under $2000, and rented for less than $100/day or from £65.00 per day in the UK for a single head machine. By comparison, FCB machines often must have a dedicated service staff.

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