High Gravity Brewing is a term that refers to the process of preparing a type of strong wort with a high original gravity, intended to produce a beer with a high alcohol content. A normal gravity wort is typically in the range of 10°–13° Plato and will result in a beer containing 4%–6% alcohol by volume (ABV).
High gravity brewing is performed by brewers for two reasons. First, it is performed to make a style of beer that has a high alcohol content, such as a German bock, Belgian tripel, or British barley wine. These types of beers are specialty styles and are generally not produced in high volumes.
The second reason a brewer might perform high gravity brewing is to meet high production demand when available brewing capacity is limited. In this regard, a brewer can make a high gravity wort that will become a high-alcohol-base beer to be used as a type of concentrate. At the final finishing steps, the brewer then adds deoxygenated brewing water to dilute the high-alcohol beer to a normal strength. Using this method, it is possible to brew a volume of beer and later increase that volume by up to 100% by dilution. Many major brewing companies and some large craft breweries use high gravity brewing to meet production demand. The technique is technically demanding, because high gravity fermentations typically produce a range of flavors and aromas that are not produced in lower gravity fermentations, and these can skew the desired flavor profile of beers produced by this method.