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Producers of spontaneously fermented beer typically do not oxygenate their wort <ref name="Beer Temple interview with De Garde"></ref> (~27 minutes in). Visual signs of fermentation (CO2 production, krausen, bubbles, etc.) generally takes 4-7 days, although we have seen reports of up to two weeks <ref name="howat_comeandbrewit">[http://comeandbrewit.libsyn.com/2016/page/2/size/25 "Episode 34- Sour Beer 102", Come and Brew It podcast. Interview with James Howat from Black Project Spontaneous Ales. 01/07/2016 (~40 minutes in).]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1183899281638284/ Conversation with Caleb Buck on MTF about spontaneous fermentation. 11/24/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1189818124379733/?comment_id=1194393553922190&comment_tracking=%7B%22tn%22%3A%22R3%22%7D Conversation on MTF with Dustin Carver on how long his spontaneous fermentation took to start. 12/14/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1213062435388635/?comment_id=1215511598477052&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Conversation on MTF with Mark B. Fry on how long spontaneous fermentation took for him. 01/13/2016.]</ref>. Traditional producers conduct fermentation for a [[File:Homebrew spontaneous fermentation.jpeg|200px|thumb|right|Spontaneous fermentation beginning in a carboy]]long time period (1-3+ years) in wooden vessels. The long fermentation process allows the different microbes present to carry out their slow metabolism of the complex carbohydrates present in the beer, developing the flavors and acidity associated with spontaneous beers (see [[Turbid_Mash#Carbohydrate_Composition_and_Utilization_Through_Fermentation|turbid mashing]] for more) <ref name="Van Oevelen et al., 1976">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1975.tb06953.x/abstract Van Oevelen et al., 1976. Synthesis of aroma components during the spontaneous fermentation of lambic and gueuze]</ref> <ref name="Spaepen et al., 1978">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1978.tb03888.x/abstract Spaepen et al., 1978. Fatty acids and esters produced during the spontaneous fermentation of lambic and gueuze]</ref>. Extended aging in the same vessel as fermentation does not present the same sort of autolysis problems that may be found in 'clean' beers aged for long periods of time on the yeast cake. There are some ideas for why this is the case, such as the extended activity of other microbes taking up autolysis products. It is also possible that the influence of autolysis is found, but that they are expressed differently in these sorts of beers and some say that the autolysis character is an important component of the beers <ref>[http://www.thebrewingnetwork.com/the-sour-hour-episode-9/ Rudy Ghequire from Rodenbach on the Sour Hour]</ref> (~28 minutes in).

On a homebrew scale a fair amount of attention has been paid to the topic of oxygen permeability in different fermentation vessels and closures <ref>[https://www.homebrewtalk.com/media/raj-apte-o2-table.58958 Raj Apte's oxygen permeability table]</ref> <ref>[http://www.mocon.com/assets/documents/PPS_Article_highq.pdf Better Bottle closure study]</ref> <ref>[https://www.youtube.com/watch?v=boLqmFIzUZ0&list=PLibE2BjPG_8H0IZe4fS2FD4uidCFhgzBn&index=4 Dan's video discussing airlocks and fermenters]</ref>. It has been suggested that sealing a glass carboy with a wooden dowel or chair leg can result in similar oxygen permeability as a wine barrel. Although this was quite a clever idea for replicating oxygen exposure, this is not recommended as it can lead to breakage of the glass carboys <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel]</ref>. While micro-oxygenation may be an important part of some spontaneous production it may be getting too much attention in homebrew carboy conditions <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel]</ref> (see comments) relative to other controls such as temperature, microbes, and time. See the [[Barrel]] page for discussions on the barrels available to homebrewers. Since spontaneous fermentations can take several days to begin (generally 4-7 days, although we have seen reports of up to two weeks), some professional brewers and a microbiologist have recommended that carboys should be filled as close to the neck as possible to limit the initial headspace and oxygen in that headspace so as to avoid [[mold]] growth (lowering the wort pH to under 4.5 will also help prevent mold growth during the early stages of fermentation) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1247501295278082/?comment_id=1247509875277224&comment_tracking=%7B%22tn%22%3A%22R%22%7D MTF post regarding mold growth in homebrew spontaneous fermentations. 03/06/2016.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1442080252486851/?match=c3BvbnRhbmVvdXMsZmVybWVudGVkLDEwMA%3D%3D MTF post regarding limiting headspace to prevent mold growth. 10/19/2016.]</ref>.