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For the traditional '''Solera''' process used in Sherry, vinegar, and brandy production, [http://en.wikipedia.org/wiki/Solera ''see the Wikipedia article on Solera'']. In beer, particularly sour beer, a single stage Solera process has been discovered to be a reliable and easy way to continuously make sour beer. Some have argued that this is a misuse of the word "solera" and that it should only be applied to multiple tiered systems (see [[Solera#Claims_of_Misuse_of_the_Traditional_Meaning|Misuse of the Traditional Meaning]] below).
The process of using a ''solera'' method in sour beer brewing has become the term used for filling a single fermenter with a sour beer, and every 6-12 months taking one third or half of the beer out for packaging (and perhaps sometimes as much as 70% is taken out, although there ). There is no set definition on defined rule for what percentage must be left behind in order the limit is to take out and still be called considered a "solera")in beer. This percentage is also variable in wine. In Sherry, a maximum of 35% can be removed, although 10-15% is more typical <ref>[https://www.sherrynotes.com/2013/background/sherry-solera-system/ Sherry Notes website. "The Solera System". 08/28/2013. Retrieved 03/06/2018.]</ref>. That The volume that is removed is then replaced with new beer or wort. This method provides the brewer with an a "perpetual" sour beer that takes less time to age because of the blended components. Over time the beer can continue to develop and change, and the brewer has the option of trying to steer the beer by altering the recipe for the wort or beer used to refill the solera. As a rule of thumb, the larger the fermenter the better. This will allow for larger seasonal pulls from the solera, thus producing more beer. The term could also be applied to a multi-vessel solera in beer, which has been argued is a more accurate use of the term, although multi-vessel solera systems in sour beer production are less common due to the potential for over exposure to oxygen.
The barrel can be refilled with either fermented beer or wort. Choosing to refill with wort could eventually lead to a lot of trub build up, however, there might not be any negative flavor effects from doing so. Wort will ferment in the barrel and might cause a blow off unless there is adequate headspace (in which case the brewer should top up the barrel after the wort ferments). Choosing to refill with beer that is first fermented with brewers yeast or with a mixed culture might be more practical for avoiding blow off issues and for group barrel projects for homebrewers because individual brewers can brew the refill beer at any time, and then meet to refill the barrel. See [[Solera#Yeast_Autolysis|Yeast Autolysis]] below.