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A spontaneous fermentation may also be achieved by inoculating small amounts of wort and growing up the spontaneously inoculated microbes to check for suitability. This is common in homebrew production <ref> [http://www.themadfermentationist.com/2011/04/ambient-spontaneous-yeast-starters.html The Mad Fermentationist Spontaneous Starters, accessed 7-May-2015]</ref> and allows for screening of the microbes to remove wild cultures with aggressive off flavors and/or mold. This is not unlike the potential of used oak barrels, where well performing barrels may be kept to inoculate subsequent batches while poorly performing barrels may be discarded and removed from the brewery. As different microbes survive and thrive in different environments, barrels or pre-screened and grown starters will probably not provide a complete profile of the microbes present in traditional spontaneous fermentation beers. However a combination of a coolship to inoculate the wort with ambient/brewhouse resident microbes combined with a form of pre-screening such as barrel re-use and/or spontaneous starters may provide the full microbiota present in traditional spontaneously fermented products. For the purposes of this page, beers receiving additions of isolated cultures or bottle dregs are not treated as spontaneous and are discussed under [[Mixed Fermentation|mixed-culture fermentation]].

The traditional production of spontaneously fermented beer employs a few main processes and goals including the production of a dextrinous wort, high hopping rates (usually with aged hops), and inoculation of the wort with a [[coolship]]. Not all breweries producing spontaneously fermented beer employ these three techniques, but they are generally common among producers.

A [[coolship]] is an open vessel used to cool wort by exposure to ambient air which traditional spontaneous fermentation brewers use to both cool their wort and to inoculate the wort with ambient microbes during the open overnight cooling. Traditionally, a coolship is a broad, open-top, flat vessel in which wort cools overnight. The high surface to volume ratio allows for more efficient cooling, which is important at commercial production scales. In addition this broad, shallow design maximizes the area of wort available for inoculation with ambient microbes. On a homebrew scale, where typical batch sizes cool more quickly, a wide shallow pan is not necessary to achieve appropriate cooling overnight given sufficiently low nighttime outdoor temperatures and the use of a wide shallow pan might result in cooling at a much more rapid rate than seen in traditional commercial production. Boil kettles and similarly shaped vessels are sufficient for overnight cooling for most homebrew batch sizes and may provide a rate of cooling more similar to that provided by coolships in commercial production sized batches <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1068826853145528/ Facebook post by James Howat] </ref>. However the aspect ratios of these sorts of vessels may limit the inoculation of the wort by ambient microbes due to the lower surface area for a given volume compared to traditional coolships. Cantillon targets a cooled wort temp of 18-20 C (64.4-68 F) after the overnight cooling <ref name="Spontaneous Sour Hour" /> (~50 min in). Traditional producers only carry out spontaneous fermentation between fall and spring when nighttime temperatures are sufficiently low (max nighttime minimum of about 8°C <ref>Conversation between Dave Janssen and Armand Debelder of [[3 Fonteinen]], July 2011</ref>) to appropriately cool the wort overnight. The ambient microbial balance may also be more favorable during this time of year (--some sources say more bacteria in summer--), but inadequate cooling could result in similar results of enhanced acid production (similar to the effect of warm incubation in [[Sour Worting|sour worting]], see also Alternative applications of ''Spontaneous Fermentation'' below). Whatever the root of the different resulting beers based on time of season/ambient nighttime temperature, producers do report different times of year/temperatures exerting a strong influence on the final beer <ref name="Spontaneous Sour Hour">[http://www.thebrewingnetwork.com/membersarchive/sourhour2015_05_wildfriendship.mp3 The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River]</ref>(~39 minutes in, ~54 minutes in).

Some more industrial producers of Belgian lambic as well as smaller North American brewers employing spontaneous fermentation acidify their wort before primary fermentation. This may eliminate the enteric bacteria step <ref name="Spitaels et al., 2015">[http://www.sciencedirect.com/science/article/pii/S074000201500012X/ Spitaels et al., 2015]</ref> (see below, Microbial Succession During Fermentation). In addition it may act as a safeguard against botulism in the beer, which can grow at the typical pH range of unfermented and unacidified wort and whose spores can survive the boiling process <ref name="James Howat presentation at NHC 2015">[http://www.ahaconference.org/seminars/wild-and-spontaneous-fermentation-at-home James Howat presentation at NHC 2015]</ref>. The degree of botulism risk is not known, though if any reported cases of botulism poisoning from beer exist they are not known to us. Traditional lambic producers have been fermenting unacidified and spontaneously inoculated wort for decades to centuries, which suggests that the risk, if it does exist at all, is very small when following traditional lambic production methods. Furthermore, hops have antimicrobial properties against gram positive bacteria <ref>[http://www.sciencedirect.com/science/article/pii/S0168160503001533/ Sakamoto and Konings, 2003. Beer spoilage bacteria and hop resistance.]</ref> and ''Clostridium botulinum'', the bacterium responsible for botulism, is gram positive <ref>[https://en.wikipedia.org/wiki/Clostridium_botulinum/ Clostridium botulinum Wikipedia page]</ref>. The degree to which ''Clostridium botulinum'' might be resistant to the antimicrobial properties of hops is unknown. Some suggest eliminating any potential worry of botulism by acidifying your wort before inoculation <ref name="James Howat presentation at NHC 2015">[http://www.ahaconference.org/seminars/wild-and-spontaneous-fermentation-at-home James Howat presentation at NHC 2015]</ref>. Whether or not this protects from botulism, it will influence the final beer by preventing enteric bacteria growth. In addition, acidifying may influence the activity of Pediococcus in a spontaneously fermented beer, including the development of "sick" beer, and may therefore alter the final beer <ref name="Spontaneous Sour Hour">[http://www.thebrewingnetwork.com/membersarchive/sourhour2015_05_wildfriendship.mp3 The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River]</ref> (~1:10 in).

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During the extended maturation phase, a beer may become "sick" or "ropey", though not all producers get this <ref name="Spontaneous Sour Hour" /> (~1:10 min in) (also Vinnie on the sunday session and maybe lambic summit). This is the result of exopolysaccarides, which some ''Pediococcus'' strains are known to produce. These exopolysaccharides can be broken down by other microbes present in the beer relieving the beer of its "sickness" (this exopolysaccaride breakdown is generally attributed to ''Brettanomyces''). A beer may also become "sick" in the bottle during bottle conditioning. This is likely due to enhanced ''Pediococcus'' activity from additional fermentable sugar, in the form of simple sugars or beer which has not completely attenuated yet. --sources for this--. A beer which is sick in the bottle will generally clear through the same process as a younger aging beer wen given appropriate time.

Much of the above discussion has focused on spontaneous fermentation as applied to lambic and lambic-inspired brewing. Some brewers are applying spontaneous fermentation to yield beers quite different from lambic-oriented brewers. A notable example of this is [[De Garde]], whose entire lineup of beers are cooled in a coolship and don't see pitched yeast <ref name="Beer Temple interview with De Garde">[https://vimeo.com/127084279 The Beer Temple Interviews #264 with Trevor Rogers of De Garde]</ref> (excepting perhaps a bit of pitched yeast in some beers for bottling conditioning). De Garde produces a range of spontaneous beers including beers similar to berliner weisse by warm incubation after spontaneous inocculation <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/814831538545062/ MTF facebook conversation with screenshot of brief De Garde process, March 2014]</ref>. By manipulation of parameters such as grist, hopping levels and incubation/fermentation temperatures, a diverse range of beers of spontaneous fermentation can be produced outside of lambic-inspired beers.