Carboys

A carboy is a large, durable container used to hold liquids. It has a wide body with a narrow neck and a stopper, bung, or cap. Carboys are commonly made of glass or plastic and are used for storage, fermentation, and transport of liquids. Typical capacities range from 1 to 6 gallons (approximately 3.8 to 22.7 liters); among hobbyist brewers, a 5-gallon carboy is a standard fermentation vessel, while winemakers may use 5- to 6-gallon sizes.

Glass carboys are usually made from borosilicate glass and can be clear or amber; amber variants protect contents from light. Plastic carboys are typically made from high-density polyethylene (HDPE) or PET and are lighter and less fragile but can scratch and may retain flavors over time. Most carboys have a narrow mouth fitted with a stopper or bung and an airlock to manage gas during fermentation. They often include built-in or integral handles on the shoulders for carrying.

Common uses include homebrewing beer and cider, winemaking, and other fermentation projects. In laboratories and industry, larger carboys are used for chemical storage and transport, though compatibility depends on the contents and the carboy material. They can also serve as temporary liquid storage or water carriers.

Cleaning and sanitation are essential, especially for fermentation. Carboys should be rinsed, sanitized with appropriate solutions (for example, Star San or Iodophor), and air-dried. Glass carboys are fragile and can shatter if dropped; use a padded surface and proper carriers or straps when moving them.

The word demijohn is sometimes used for smaller glass bottles, while carboys are generally larger.