Editing Fermentation lock

{{short description|Device used in beer brewing and wine making}}
{{More citations needed|date=January 2021}}
[[Image:Homebrew Airlock.jpg|thumb|right|150px|Fermentation lock on [[homebrewing]] fermentation vessel]]
[[Image:CarboyHomebrew.jpg|thumb|upright|180px|A {{convert|6+1/2|usgal|L|order=flip|abbr=on|0}} glass carboy acting as a fermentation vessel for beer. It is fitted with a fermentation lock.]]

A '''fermentation lock''' or '''fermentation airlock''' is a device used in [[beer]] [[brewing]] and [[wine making]] that allows [[carbon dioxide]] released during [[fermentation]] to escape the fermenter, while not allowing [[Atmosphere of Earth|air]] to enter the fermenter, thus avoiding [[Redox|oxidation]].

There are two main designs for the fermentation lock. These designs work when half filled with [[water]]. When the [[pressure]] of the [[gas]] inside the fermentation vessel exceeds the prevailing [[atmospheric pressure]] the gas will push its way through the water as individual bubbles into the outside air. A sanitizing solution, [[sulfur dioxide|sulphur dioxide]]<ref>{{cite web
 |archive-url=https://web.archive.org/web/20170704101031/http://www.zusatzstoffe-online.de/zusatzstoffe/63.e220_schwefeldioxid.html
 |url=http://www.zusatzstoffe-online.de/zusatzstoffe/63.e220_schwefeldioxid.html
 |title=E220 Schwefeldioxid
 |website=Zusatzstoffe Online
 |publisher=Die Verbraucher Initiative e.V.
 |access-date=2017-07-04
 |archive-date=2017-07-04
 |language=DE
}}</ref> or [[ethanol|alcohol]] is sometimes placed in the fermentation lock to prevent [[contamination]] of the [[beverage]] in case the water is inadvertently drawn into the fermenter.

This device may take the form of a tube connected to the headspace of the fermenting vessel into a tub of sanitized liquid or a simpler device mounted directly on top of the fermentation vessel.

Currently, a popular fermentation lock that mounts on top of the fermentation vessel is the three-piece fermentation lock.  Other models contain three bulbous chambers allowing for a broader range of pressure equalization.  These bulbous fermentation locks were generally made of hand blown glass and are nowadays often made of clear plastic.

The use of perforated rubber [[balloon]]s offers an easy and inexpensive alternative to conventional airlocks: as used primarily in [[homebrewing]], the balloon is stretched over the orifice of the fermentation vessel and, if necessary, tightened with [[rubber band]]s. The balloon is then perforated with a needle. These punctures, while not completely airtight, sufficiently protect the vessel's contents from contamination and allow the gases produced by fermentation to evacuate from the vessel as the pressure rises and the balloon inflates.

== See also ==
*[[Fermentation (wine)]]
*{{section link|Brewing|Fermenting}}
*[[Harsch crock]]
*[[Gas bubbler]]

==References==
{{reflist}}

{{homebrewing}}

[[Category:Homebrewing]]