Soda water, also known as seltzer or carbonated water, was for many years prized for its supposed health benefits. Until the discovery of the technology enabling its manufacture, soda water was available only from natural soda springs, and it was often bottled and used to produce a variety of health tonics. These tonics were the origin of many modern soft drinks. Although it is no longer believed to provide health benefits, it still is a popular and refreshing beverage that can be manufactured on either a small scale or large scale.
The manufacturing process used for producing the soda water that is used in commercial soft drinks is conducted on an industrial scale. This process, known as carbonation, is accomplished by first lowering the temperature of tap water to 46 degrees Fahrenheit (8 degrees Celsius). A strongly basic and water-soluble source of bicarbonate such as such as sodium or potassium bicarbonate is then added to the chilled water to raise its potenz hydrogen (pH) level and to compensate for the sour flavor of carbonic acid. The solution is subjected to pressurization with carbon dioxide gas, which dissolves in the water to form carbonic acid, again lowering the solution's pH. The carbonated water is then added to a tightly sealed container pressurized to 120 pounds per square inch (830 kPa) with further carbon dioxide gas to keep the water carbonated.
In commercial establishments that use a great deal of soda water when making mixed drinks, the cost of purchasing it pre-made can be prohibitive. Soda water can instead be produced on-site using small, mechanical carbonators. These machines pre-pressurize tap water with carbon dioxide. This pressurized water is kept in corrosion-resistant stainless steel barrels, preventing the acidity of the carbonic acid from damaging the containers. To produce fresh soda water, carbon dioxide merely needs to be injected into the pressurized water.
Although the use of home carbonators declined in the late 20th century, there was a resurgence in the early 21st century in interest in do-it-yourself carbonation for making mixed drinks by home bartending aficionados. Although this is in part because of the elevation of owning retro home appliances in modern fashion, some people prefer the natural tartness of carbonated water that is produced without the addition of chemicals to reduce its acidity. Home soda water can be produced using soda siphons and single-use pressurized carbon dioxide gas cartridges, which can be found easily online through specialty suppliers.