A typical batch of homebrewed beer is 5 gallons (19L) in size (roughly enough for 2 cases - or 48 12-ounce bottles - of beer), and is produced by boiling water, malt extract and hops together in a large kettle, then cooling the mixture - called wort - and adding yeast (called pitching) for fermenting. The concentrated wort is filtered (called sparging) into a fermenter filled partly with cold water to bring the wort to proper concentration, and to cool down to pitching temperature (70-75F). Often, cooling is aided by a variety of "wort chillers" consisting of copper tubing through which cold water flows. Primary fermentation takes place in a bucket or large glass container (called a carboy) that vents the carbon dioxide gas produced through a small device called a fermentation lock. A layer of sediment appears at the bottom of the fermenter (called trub, rhymes with tube). Often, the beer is siphoned (racked) into another fermenter (called a secondary) to finish fermentation without the trub lending off flavors. Once this fermentation subsides, a small amount of additional sugar (called priming sugar) is added and the beer is transferred to bottles that are then capped. The carbon dioxide produced by fermentation of the priming sugar in the bottles remains in the beer causing carbonation. The whole process can take from two weeks to several months, depending on the style of beer. Some enthusiasts brew in far larger quantities, sometimes as a prelude to commercial production.
Advanced homebrewers often prefer to brew "all-grain" batches of beer, by mashing the grain themselves to reduce starch into sugars needed by the yeast. Such techniques allow a greater control over the final quality of the beer than malt extract brewing. A large vessel called a "mash tun" holds the water at various temperatures to break the startch in malt into fermentable sugars which become alcohol and dextrins (unfermentable carbohydrates) which give the beer body. The spent grain is removed ("sparged") in a perforated container called a "lauder tun" and brewing proceeds as normal. Often, homebrewers use one vessel with a perforated false bottom for both mashing and laudering. A hybrid called "grain extract", or "partial mash" uses both home-mashed malt and malt extract. This method is preferable to those who do not want to invest in larger equipment required for all-grain brewing, but would like to experiment with mashing grain.
In 1978, Jimmy Carter signed into law a bill explicitly allowing home beer and winemaking. Note that distillation of alcohol is still illegal in the home. People homebrew for a variety of reasons. Homebrewed beer can be cheaper than commercially equivalent brews, however most homebrewers customize their recipies to their own tastes, which tends to more expensive. For instance, "hopheads" can hop their beer far beyond what would normally be considered excessive, or fans of bitter, dark beer can create beers that are the antithesis of the commercially dominant American lager style. Some homebrewers strive for perfection of specific styles of beer and enter their products in competitions.