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Packaging is the transfer of your mixed fermentation/sour/funky beer from a fermentation or aging vessel into the the final package (e.g. a bottle or a keg). This page will discuss various things one should consider such as when to package, how to package and what final package to put the beer into. For information on packaging with corks and in large format bottles, see the Corking page. See Aging and Storage for storage information.

When to package

Final Gravity

There is no hard and fast rule for when to package based on final gravity because the gravity of the finished beer will depend on recipe, process, and microbes present among other factors. Generally, lower final gravities are safer because they constrain the extent to which the beer can continue to ferment and generate extra CO2 in the package. But rather than looking for a specific number, pay more attention to the stability of the gravity. Jay from the Rare Barrel recommends waiting at the final gravity for 2-3 months in mixed fermentation beers to ensure that this gravity is the actual final gravity [1] (~38 minutes in). If the gravity is stable over a long time scale (weeks to months, depending again on factors such as the recipe, process, and microbes present), then the beer is probably done. If you are unsure then give the beer a bit longer and monitor final gravity. Keep in mind that sampling sour beer too often can lead to too much oxygen exposure, and care should be taken not not sample too much and purge with CO2; see Mixed Fermentation for more information. Each gravity point (.001) of continued fermentation yields roughly 1/2 volume of CO2 (each degree Plato yields 2 volumes of CO2) [2]. Sometimes beer samples will contain high amounts of carbonation due to gradual fermentation from Brettanomyces (in other cases when the beer has aged for a very long time, there may be much less residual carbonation than normal). Therefore, it is best practice to degas the sample by pouring it through a membrane filter such as a coffee filter in order to obtain an accurate gravity reading [3].

With continual batches of beer using the same grist and strains of microbes, a stable final gravity can become more easily predicted by the brewer and waiting for a stable final gravity may no longer be necessary once a known stable final gravity is achieved (note that a change in the strains being used or the grist could result in a different stable final gravity). For example, see the Brettanomyces and Saccharomyces Co-fermentation page for techniques for inoculating Brettanomyces at bottling time into a clean beer that was fermented with just S. cerevisiae.

If fruit was added to an already matured mixed fermentation beer with living Brettanomyces in it, an additional 1-2 months should be given after adding the fruit to ensure that the sugars from the fruit are fully fermented. See Soured Fruit Beer Refermentation for details on using fruit in sour beers.

For suggested equipment for reading gravity from small samples, see Density Meters.

Flavor Development

While determining if the final gravity is stable is the most important factor when choosing when to package mixed fermentation beer, there are also different approaches to choosing when to package beer based on the flavor maturity of the beer. For Mixed Fermentation beers that contain Brettanomyces and lactic acid bacteria, months are often required for the beer to reach an optimal or even just acceptable flavor profile. This depends on many variables such as is the beer aging in an oak Barrel, what microbes are pitched (for example, Pediococcus and slower species of Lactobacillus such as L. delbruekii tend to need a few months to develop acidity), what flavors the brewer is looking for, etc. If the gravity is stable, some brewers prefer the option of packaging the beer before the flavor is optimal and allowing the flavor to continue to develop in the bottle/keg. This gives the advantage of being able to sample the beer at different points in time and can serve as a good technique for learning how a particular culture ages. If this approach is taken, keeping the bottles/kegs at room temperature instead of at refrigerator or cellar temperatures is advised so that the yeast and bacteria do not fall dormant. Colder temperatures will slow the maturation of the beer. Other brewers prefer to allow the maturation of flavors to happen in the fermenting vessel (especially in the case of oak barrels), and then package the beer when it tastes good. This approach is less risky as far as potentially packaging a premature beer that never fully reaches the flavor profile that the brewer finds acceptable. In other words, sometimes mixed fermentation beers never taste good, and allowing the beer to bulk age in the fermenting vessel allows the brewer to make sure the beer is worth packaging.

For more information on when mixed fermentation beers are ready to package based on flavor, see the various Brewing Techniques pages. For more information on aging and cellaring packaged beer, see Aging and Storage.

Clarity and pellicles

Beer with Brettanomyces and bacteria, as well as certain Saccharomyces strains, will take longer to clear than other beers. Generally, time can take care of most of the clarification in mixed fermentation beers with long aging times. Faster turnaround beers or kettle sours may not clarify by time alone. The level of clarity you are looking for before packaging will depend on your preferences and the beer you are making. Beer can be packaged without good clarity and they will continue to settle out in the bottle, but note that beers with high carbonation levels may kick the sediment back into suspension, which may or may not be what you want in your beer.

Some producers will coarse filter their fruited or dry hopped sour beers to prevent pieces of fruit from clogging equipment or making it to the package [4][5]

Beer with a pellicle can be bottled, and it is not necessary to wait for a pellicle to disappear before bottling. See Pellicle for more information.

How to package



When bottling or priming a keg at packaging time, the brewer should consider re-yeasting. In a long aged beer, especially an acidic beer, the Saccharomyces will mostly be dead already. This leaves Brettanomyces in charge of conditioning the beer. Although some lactic acid bacteria are capable of producing CO2, their contribution is probably negligible. It is also possible that homofermentative LAB will consume a portion of the sugar before the Brett has a chance to produce CO2. Re-yeasting is a very effective way to ensure proper CO2 levels in an aged sour beer. Another benefit of re-yeasting is that it tends to help avoid (or minimize) Tetrahydropyridine production.

Commercial producers and MTFers have had success re-yeasting with their mixed culture, wine yeast, and champagne yeast. The specific yeast you choose is up to you, and we recommend that you try a couple different yeasts out to find the one you prefer (MTFers have reported success with Lalvin EC-1118 Champagne, Red Star Premier Cuvée, Red Star Pasteur Blanc, Danstar CBC-1, Fermentis T-58, Scott Laboratories DV10 wine yeast, and fresh cultures of Brettanomyces [6]). When re-yeasting at bottling for a beer that has some residual gravity (a higher than 0 plato or specific gravity), take care not to use a highly attenuative yeast that could over-attenuate the beer in the package. For example, adding Brettanomyces or a diastatic strain of Saccharomyces cerevisiae at bottling to a beer that has some residual sugars could result in over-carbonation in the bottle [1] (~41 minutes in). If the beer has a significantly high finishing gravity, then re-yeasting with a yeast that beer has already seen should eliminate the possibility of continued attenuation as long as the beer is already at final gravity. Using rehydrated dry yeast has been shown to be more reliable than both slurries and even freshly propagated yeast probably due to their rich sterol reserves (this excludes freshly propagated yeast using acid shock starters - see below) [7][8]. Brewers who are having difficulty carbonating sour beer or need to ensure that the beer will carbonate properly should grow their yeast first in an Acid Shock Starter. This will acclimate the yeast to the harsh conditions of the sour beer, and has shown to be more effective for ensuring bottle carbonation [9]. Not all sour beers will need the priming yeast to be acclimated, but sour beers with darker malts, acidic fruits, and high ABV (8%+) might require this step. See Acid Shock Starters below, and fermenting in low pH conditions for more information on the science behind this technique.

The yeast required for carbonation is very little. A good rule of thumb to use is to use 10% of the yeast that you would normally use for a primary fermentation (approximately 1 million cells per mL). For example, for dried yeast use ~2 grams of yeast for 5 gallons of beer [10]. Rehydrating the yeast is recommended. See Jeff Crane's "Blending Calculator" (extension of Michael Tonsmeire's "Blending Calculator") for a re-yeasting and priming calculator. Dry yeast should be rehydrated in ten times its weight in 80-90°F (27-32°C) water for ~15-20 minutes [11].

Many wine yeast strains are known to be "killer" yeast strains. In Saccharomyces, killer strains produce toxins that kill sensitive strains. Neutral strains do not produce toxins, nor are they killed by them [12]. Almost all ale and lager strains are sensitive to the toxins produced by killer strains [13][14]. In Saccharomyces, four toxins have been identified: K1, K2, K28, and Klus, the first three of which can only kill other strains/species of Saccharomyces. The Klus toxin has been found to kill yeast from other genra, such as Hanseniaspora spp., Kluyveromyces lactis, Candida albicans, Candida dubliniensis, Candida kefir and Candida tropicalis, and the K1, K2 and K28 killer strains of S. cerevisiae [15]. However, none of the toxins have been found to kill Brettanomyces [16]. The K1 toxin is most active between a pH of 4.6 and 4.8, while K2 and Klus are active around a pH of 4.0 to 4.3 [15]. See Killer Wine Yeast for more information on these toxins.

This tends to create some fears for brewers who believe that the Saccharomyces strains in their beer might still be alive. However, in a highly acidic sour beer, Saccharomyces wine strains tend not to live for extended periods of time [17]. Even if some cells do, their activity would be next to none due to no available sugars left in the beer (other than priming sugar), and thus their contribution to the flavor development of the beer would be minimal to none. Assuming good bottling practices are followed, fear of autolysis occurring due to killer strain activity is usually unfounded because most of the Saccharomyces cells are left behind with the trub at bottling. Additionally, Brettanomyces has the ability to metabolize the acids and proteins that are released during whatever autolysis that might occur in the bottle. Re-yeasting with wine yeast for priming has the additional advantage of not fermenting maltose or maltotriose, so unexpected attenuation from the wine yeast will generally not occur as long as the beer is already fully attenuated. Thus, there is little argument against re-yeasting with wine yeast at packaging time, other than a desire to approach carbonation in a traditional sense such as is the case with lambic.

The flavor impact by the wine yeast in beers that contain living Brettanomyces is also probably minimal or not significant, although this has yet to be established scientifically [18]. This would be due to the small amount of fermentables provided by the priming sugar, as well as the ability of Brettanomyces to metabolize many secondary metabolites that would be produced by a bottling yeast. It has been shown, however, that bottling yeast in general can have a flavor impact on clean beers without Brettanomyces. For example one study found that out of 5 dried yeast strains from the Lallemand Yeast Culture Collection (Montreal, QC, Canada), one strain produced a higher final pH by about ~.05 (from 3.98 to 4.02 pH) in a Belgian dark ale (no Brettanomyces or other non-traditional microbes were used in the beer). The various strains tested also affected the levels of acetic acid, ethyl acetate, isoamyl alcohol, acetaldehyde, diacetyl, and glycerol in beer just from bottle conditioning [11]. Some brewers speculate that thiols from wine yeast could also create novel characteristics in beer (although perhaps not from only bottle conditioning yeast) [19]. It could therefore be possible that metabolites produced from bottling yeast could have an effect on sour/"Brett" beer flavor as well, but this remains to be demonstrated scientifically.

Acid Shock Starters

Below are several acid shock starter techniques for acclimating yeast to the harsh conditions of acidic wort or beer, including mixed fermentation sour beers and kettle sour beers. See fermenting Saccharomyces under low pH conditions for more information on the science behind this.

Escarpment Labs Acclimation Protocol

The following acclimation protocol has been adapted for sour beer from Richard Preiss's instructions on how Escarpment Labs acclimates wine yeast: [20]

  1. Take a "pinch" of rehydrated dried yeast, and pitch 150,000 cells/mL into 100 mL of YPD + Go-Ferm Media. Grow for ~24 hours at 86°F (30°C) with shaking.
  2. Transfer the starter into 100 mL of Adaption Media 1. Grow for ~24 hours at 86°F (30°C) without shaking.
  3. Transfer the starter into Adaption Media 2 (whatever volume is needed for batch size). Grow for ~24 hours at 86°F (30°C) without shaking.
  4. Pitch ~1 million cells per mL of sour beer that is being carbonated, along with priming sugar.


YPD + Go-Ferm Media (autoclaved)
0.02375 g/L Go-Ferm
10 g/L yeast extract
20 g/L peptone
20 g/L dextrose
Adaption Media 1 (filter-sterilized)
10% base sour beer
20 g/L sucrose
0.02375 g/L Go-Ferm
Adaption Media 2 (filter-sterilized)
70% base sour beer
20 g/L sucrose
0.2 g/L Fermaid

Homebrew/Low Tech Acclimation Method

This method was adapted from the Escarpment Labs and the Rogers et al. methods using non-laboratory processes and ingredients.

This method has not yet been validated as far as producing the correct pitching rate for re-yeasting, which is suggested to be 1 million cells per mL of beer.

For ~20 liters (or around 5-6 gallons) of sour beer:

  1. Measure 1-2 grams of dried yeast, and re-hydrate in a little bit of warm water.
  2. Measure 50 mL of the sour beer that is going to be carbonated, and combine it with 100 mL of apple juice with no preservatives (or use DME if using a beer yeast strain) and a pinch of Go-Ferm in a saucepan.
  3. Heat pasteurize the sour beer, apple juice, and Go-Ferm mixture on the stove at 160°F for 10 minutes.
  4. Cool the sour beer and apple juice mixture to around 86°F (30°C). Pitch into an Erlenmeyer flask, along with the re-hydrated wine yeast.
  5. Grow for ~24 hours without shaking at around 86°F (30°C) *.
  6. Measure 200 mL of sour beer that is going to be carbonated, and combine with 200 mL of apple juice and a pinch of Go-Ferm in a saucepan.
  7. Heat pasteurize the sour beer, apple juice (make sure there are no preservatives in the apple juice), and Go-Ferm mixture on the stove at 160°F for 10 minutes.
  8. Cool the sour beer and apple juice mixture to around 86°F (30°C). Top up the Erlenmeyer flask with the yeast starter in it with this fresh mixture.
  9. Grow for ~24 hours without shaking at around 86°F (30°C) *.
  10. Continue to step up the starter as needed for larger batches.
  11. After the 24 hours of growth is finished for the final step, add ~200 mL of the starter per 20 liters of beer (stir the starter before adding into the beer; this does not account for the sugar that needs to be added to achieve carbonation because the apple juice should be fully fermented at this stage).

* If a fermentation temperature of around 86°F (30°C) cannot be maintained and the temperature falls during the 24 hour growth period, allow the final step to ferment for 48 hours before adding it to the beer just to make sure the apple juice is fully fermented.


If your beer is at final gravity, you can prime it as you would any normal beer based on the amount carbonation you want. In order to properly prime your beer, you will need to know your residual CO2 in solution. This can be determined by temperature and good priming sugar calculators take this into account. For aged beers, especially beers which have been aged in barrels or a similar porous vessel, the starting CO2 may be lower than the numbers produced from these calculators due to off-gassing while the beer is aging. We recommend using Jeff Crane's "Blending Calculator" (extension of Michael Tonsmeire's "Blending Calculator") for priming calculations with aged beer.

Tomme Arthur from The Lost Abbey reports that the starting values he sees in barrel aged beers range from 0.2-0.6 volumes of CO2[21] (~51 minutes in). Brewers may choose to partially force carbonate their beers to know the starting CO2 exactly as well as limit the CO2 required from bottle conditioning. The Lost Abbey carbonates to 1.5 volumes of CO2 before priming and bottle conditioning for the remaining carbonation[21] (~52 minutes in). Alternatively, a product used in measuring residual CO2 for champagne called a Carbodoseur can be used to estimate residual CO2 after long aging. See these MTF threads on experiences using the Carbodoseur and the Carbodoseur calibration table. If no effort is made to determine residual CO2, 0.4 has been quoted as a good estimation for aged beer [22].

If your beer is not at final gravity, but you have a good idea of where it will finish, then you can prime taking into account remaining gravity points. See Final Gravity for more information.

Alternatively, beer can be kegged and force carbonated like any other beer. Beer can be then bottle/crowler/can filled from the keg using a beer gun or some other device. Anecdotes from some brewers have reported a higher chance of THP production when force carbonating some mixed fermentation beers (see the THP page for more information). See Package Types below for more information on kegging in general.

CO2 levels in bottles can be measured with special equipment. For example, Allagash uses a Haffmans CO2-Selector. The pierce model Zahm can also be used to measure packaged CO2 levels (see this MTF thread).

See also:

Bob Sylvester's Priming Guide

Bob Sylvester from Brasserie Saint Somewhere describes his method to bottle conditioning saison/farmhouse style beers on a commercial scale (amounts are for a 7 barrel/217 gallon batch of beer) [23]. This method achieves high carbonation levels that are appropriate for saison styles, which targets about 2.5 volumes and is low enough to account for some minor attenuation in the bottle [24]. The sugar levels listed assume the beer is not barrel aged and has residual volumes of CO2 (approximately 0.86) [25]:

  1. All my beers have a final gravity of pretty much zero. I use plain cane sugar. I've found it to be pretty yeast friendly and the results are faster with sucrose. Not sure why dextrose became popular. Most of us don't brew with corn, so why add it at packaging.
  2. Bob prefers Red Star brand dry champagne yeast. Suggested alternatives include EDM wine yeast, Maurivin PDM, and Fermentis Safoeno VR 44 [26].
  3. For 7 barrels/217 gallons of beer, dissolve the 12 pounds of cane sugar (0.88 ounces of sugar per 1 gallon of beer) in ~3.5 gallons of 108-110°F water. After the sugar dissolves, add 250 grams of yeast to the sugar water (1.15 grams of yeast and 0.885 oz of sucrose dissolved in 2 fl oz of water per gallon of beer, or 6.628 grams of sucrose per liter of beer). The amount of yeast is less important than the amount of sugar [26])[27]. I do this first and let it bloom while I transfer the beer from the fermenter to my kettle. Takes about 20-30 minutes. By this time the yeast is about to crawl out of the bucket. Editor's note: many homebrewers have had success carbonating sour beer with only 1-2 grams of wine yeast for 5 gallons of beer.
  4. Add the yeast/sugar slurry just before the transfer is finished as this will help incorporate the slurry. Carbonation happens the same day as packaging if done correctly.
  5. Sounds counter to everything you've learned, but don't gas purge the bottles. The yeast will uptake the O2 in the head space.
  6. Sanke keg conditioning uses the same exact process but back the sugar down to 8 pounds (0.59 ounces of sucrose per gallon of beer or 4.4186 grams of sucrose per liter of beer) and keep the yeast at 250 grams. Fill the keg to the shoulder where the side and the lid meet (too much headspace leads to too high of a carbonation level). One recommendation for getting the right headspace is to lift one side of the keg onto a 2x4 wood block and fill it while the keg is leaning at an angle (this method works best for half barrel kegs; smaller kegs might tip over) [28].
    1. Note: For a discussion on why or why not the dosage of priming sugar for kegs should be lower than for bottles, see this thread.
  7. Wait 10 days. That's it. With time, the initial "rough" carbonation you get in the first couple days will mellow out into the fluffy stuff.


David Fuhrer reported using a "speise" method similar to krausening for mixed fermentation beers reduced the time of THP in mixed fermentation bottles to 3 weeks. See Episode 237 of the MBAA podcast and related links.

See also:

Oxygen exposure

Oxygen is the enemy of finished beer, and most producers of standard beers invest a lot of time and money into reducing oxygen exposure in their finished beer (referred to as "dissolved oxygen" for oxygen in the beer or "total packaged oxygen" for total oxygen in the beer plus additional oxygen in the headspace of the package). Excessive oxygen exposure can negatively impact the beer either permanently through the formation of acetic acid and/or ethyl acetate, temporarily by increasing tetrahydropyridine (THP) formation, or through the oxidation of various compounds. For mixed fermentation beers where fresh bottling yeast is added, this may not be as significant of a concern, depending on how much oxygen is allowed to enter the packaging. These beers, especially barrel aged versions, generally have more oxygen exposure during fermentation and aging, and this contributes to the characteristics of the beer. Brettanomyces is known as an "oxygen scavenger", which helps to prevent oxidative reactions in the bottle over time (see Aging and Storage). Fresh bottle conditioning yeast can help prevent acetic acid and THP production by consuming the oxygen in non-purged bottles before it can have an effect on the mixed culture. Even without fresh bottling yeast, some brewers achieve good results without purging bottles before filling (for example, lambic producers and blenders), although this might be dependent on whether the strains present in the beer are big THP producers or if the brewer has limited time to store bottles long enough for the THP to age out. Others do take care to avoid oxygen exposure in the packaging process and report that purging bottles with CO2 helps prevent THP formation. Due to these many variables, there is no easy answer in terms of whether it is better to carefully CO2 purge as is standard practice for clean beers. CO2 purging can require more expensive equipment, as well as require more time to package. Based on the characteristics of the microbes being used, experience, equipment, process, and preferences, the brewer can determine how much limiting O2 exposure during packaging is necessary. The safest route is to treat them as you would a normal beer and take care to avoid O2 where this is possible or affordable, though the experience of some will say that this extra work and cost might not be completely necessary like it is for clean beers.

If force carbonating the beer instead of bottle conditioning with fresh yeast, or if bottle conditioning without adding fresh yeast, it might be best practice to purge bottles and kegs with CO2 in order to limit the production of both acetic acid and THP. Again, experience should drive this decision one way or the other.

See also:

MBAA podcasts:

Package and closure types

(in progress) Many sour/funky/mixed fermentation beers are highly carbonated. It is recommended to package highly carbonated beers in bottles of thicker glass which can better withstand higher pressure (e.g. many Belgian and German bottles, corkable Champagne-type or 'fat-lipped' Belgian-type bottles, etc.). This is especially true if you feel the beer may continue to carbonate in the bottle from residual carbohydrates beyond the priming sugar you added. Be careful when carbonating your beer to high volumes to ensure that your chosen package can handle this pressure.

For information about corking, see the Corking page.

  • Crown caps (26 mm) - A variety of thicker glass/high-pressure bottles are available in the standard 26 mm cap size. No special equipment, beyond a normal capper, is necessary to fill bottles of this type. It may be necessary to swap the metal plates on cappers such as the Emily capper to accomodate the wider neck on some bottles taking a 26 mm cap (such as champagne-style bottles with 26 mm caps (e.g. Logsdon, Goose Island, some Upright) and the 375 mL crown finish bottles modeled after the 'Vinnie' 375 mL bottles).
  • Crown caps (29 mm) - For capping bottles with 29 mm openings (such as Champagne-style bottles and 375 mL half-Champagne bottles), you will need to source a 29 mm bell and 29 mm caps, which are non-standard. Many 29 mm bottles are both capable and corkable. For cork and capping, see below.
  • Swing tops - Many swing tops are thicker glass and are therefore well suited for higher carbonation beers. Swing tops also allow for easy venting of carbonation if the beer carbonates more than desired/anticipated. Due to the soft gasket (and possibly plastic top piece holding the gasket for some bottles), the same concerns regarding cleaning difficulty and cross-contamination apply to swing tops as to other plastic parts used after the hot side when brewing both normal and 'funky' beers. If you don't want your normal beers exposed to the micro-organisms in your funky beers, we recommend not using the same swing tops for bottling both types of beer, jusrt as we recommend keeping seperate sets of plastic equipment used for fermentation and transfer of fermented beer when brewing both clean and 'funky' beers. Some express concern about long term aging in swing tops and the possibility of swing tops not being as impermeable a barrier to O2. If you are concerned about this they it may be better to not use swing tops for long aged beer. At this time we are unaware of any comparisons of swing tops and other closure mechanisms regarding their susceptibility to O2 transfer during extended aging to give a firm answer as to whether swing tops allow more O2 ingress than other closures or not .
  • Kegging - Kegging offers the benefit of being able to force carbonate or naturally carbonate with adding priming sugar and (optionally) re-yeasting. If force carbonating, follow the same procedures that you would for any other beer. Consider the "set and forget" method of force carbonating, which requires 1-3 weeks. This will allow the beer to settle while also dialing in the carbonation level. Priming in the keg often produces great results with sour beers. Generally, use 1/2 of the priming sugar that you would normally use, or excessive foaming can occur [29]. If re-yeasting, which is generally recommended (see the Re-yeasting section above), use 10% of the yeast you would normally use to for a primary fermentation. For example, use around 2 grams of dried champagne yeast re-hydrated to naturally carbonate 5 gallons of beer [10]. Priming in the keg will result in a little more sediment at the bottom of the keg, but this will be pulled out on the first pour from the keg. Allow at least three weeks of conditioning at room temperature, and then a week at refrigeration temperatures before serving. If the keg is not re-yeasted, it might take considerably longer than three weeks to carbonate the beer depending on the vitality of the yeast in the beer. The brewer should consider keeping plastic kegging equipment such as serving lines and taps separate from kegs that serve clean beers.
A spunding valve can also be used to help guard against over-carbonation when keg conditioning. The CO2 gauges on spunding valves can be inaccurate, however, so finding the correct PSI setting requires the following technique. The goal is to set it to be around 30 PSI for room temperature conditioning. First, pressurize the keg to 30 PSI using a reliable CO2 regulator, then remove the gas line while the keg is still pressurized. Fully tighten the spunding valve's pressure release valve (PRV) so that no gas is released, and attach it to the keg's gas line. Slowly turn the PRV on the spunding valve so that the gas is released. Continue to release the gas until the faintest "hiss" of gas can be heard, and then slightly tighten the PRV. The PRV might be set to something like 40 or 50 PSI, but the reliable CO2 regulator can be used to verify that the spunding valve's PRV is set to the desired level. The actual PSI within the keg might oscillate around 27-32 PSI, so this technique might need some trial and error. Shoot for under-carbonation versus over-carbonation. If the beer is slightly under-carbonated, force carbonation can make up the difference. Slight over-carbonation should be avoided because it could make the beer very difficult to serve [30].
Another method for setting the spunding valve's PRV to the correct PSI setting would be to use a keg of beer that is already perfectly carbonated. Allow the keg to warm to conditioning temperatures. Attach the spunding valve with the PRV completely closed. Slowly release the PRV until you hear a slight hiss. This should reach the PSI setting that the spunding valve needs to be set at to reach around the same carbonation for other kegs. Kegs should be filled up to the same headspace as the keg that was used to set the PRV setting [31].
  • Green glass v Brown glass - Some bottle types, especially champagne style bottles, may be more available in green glass compared to brown glass. Green glass does a worse job shielding the beer from UV spectrum light, which can interact with hop compounds to produce 'skunky' or lightstruck flavors and aromas. Many classic Belgian mixed fermentation beers are found in green glass, and some producers in North America seek out green glass over brown glass for their beers [32][33] (~11 minutes in) (also, Bob Sylvester). See also Lightstruck.
  • Crown caps v corks - Deciding between corks and caps will depend on the specific beer and the brewer's goals with the beer. Caps are a cheaper closure and are also easier to apply. Aside from aesthetics, you may choose corks when intending to age or store beers lying down in order to keep the beer from interacting with the cap. Some producers have observed that crown caps contribute to an off-flavor in their beer, especially if the beer is acidic. Pierre Tilquin closes some bottles of every blend with crown caps in order to test carbonation levels. He has noticed that the crown capped bottles have an off flavor not present in the corked bottles [34]. Other producers regularly package their acidic beer with crown caps (e.g. the Rare Barrel, Boon Geuze in 25 cl bottles) and have not mentioned a problem with doing so.


See Corking and Floor Corker fore more information on corking and using floor corkers.


Usually, only pasteurized sour beer is canned due to the danger of over-carbonating canned beer, however, some brewers have been experimenting with canning mixed fermentation beer and allowing the beer to naturally carbonate in the cans. It is recommended that brewers contact their can supplier to verify that the plastic liners for the cans are rated to handle the pH of sour beer (3-4 pH; kettle soured or otherwise) and to find out the lifespan of the cans. Cans have been found to preserve some hop compounds such as myrcene and caryophyllene better than bottles because bottle caps can strip some of these compounds [35].

See also:


Using Sulfite

It may be possible to use sulfite to inhibit refermentation of unfermented sugars.


Bottle Suppliers

Single Cases


Bulk 29mm Caps

See also:

Corkers, Corks, and Cages

See Corking.

Bottle Fillers

Cheap and DIY

Mid Tier Products

Wire Storage Containers

Label Makers

Efficient label makers starting at around $1500 USD.


Density Meters



Mobile Canners

Companies that can sour/funky beer.


See Also

Additional Articles on MTF Wiki

External Resources


  1. 1.0 1.1 The Sour Hour episode 6 Listener Q&A
  2. "Accurately Calculating Sugar Additions for Carbonation." Kai Troester. Retrieved 08/07/2016.
  3. "Recommended Beer Degassing Methods and Alternatives Matrix". ASBC Methods of Analysis. Retrieved 03/04/2020.
  4. Casey Brewing & Blending fruit strainer
  5. Jean at Cantillon making a filter
  6. Conversation on MTF regarding bottle conditioning yeast. 11/21/2016.
  7. an Landschoot, A., Vanbeneden, N., Vanderputten, D. and Derdelinckx, G. (2004). Effect of pitching yeast preparation on the refermentation of beer in bottles. Cerevisia 29:140-147.
  8. Van den Berg, S., Demeyere, K. and Van Landschoot, A. (2001). The use of dried yeast for the bottle refermentation of beer. Cerevisia 26:102-108.
  9. Terminal acidic shock inhibits sour beer bottle conditioning by Saccharomyces cerevisiae. Cody M. Rogers, Devon Veatch, Adam Covey, Caleb Staton, Matthew L. Bochman. 2016.
  10. 10.0 10.1 Blending Calculator - pH, ABV and Carbonation. Jeff Crane. Blending Calculator - pH, ABV and Carbonation. Bikes, Beer, & Adventures Blog. June 12, 2015.
  11. 11.0 11.1 S. M. Van Zandycke, T. Fischborn, D. Peterson, G. Oliver, and C. D. Powell (2011). The Use of Dry Yeast for Bottle Conditioning. MBAA Technical Quarterly. doi:10.1094/TQ-48-1-0225-01.
  12. Advances in Microbial Physiology, Volume 22. Academic Press, Sep 15, 1981. Pg 94-95.
  13. Conversation with Bryan of Sui Generis Blog on MTF on Killer Factor for Saccharomyces. 11/16/2015.
  14. Strains of Yeast Lethal to Brewery Yeasts. A.P. Maule and P.D. Thomas. 1972.
  15. 15.0 15.1 A New Wine Saccharomyces cerevisiae Killer Toxin (Klus), Encoded by a Double-Stranded RNA Virus, with Broad Antifungal Activity Is Evolutionarily Related to a Chromosomal Host Gene. Nieves Rodríguez-Cousiño, Matilde Maqueda, Jesús Ambrona, Emiliano Zamora, Rosa Esteban and Manuel Ramírez. 2011
  16. Non-Saccharomyces killer toxins: Possible biocontrol agents against Brettanomyces in wine? S. Afr. J. Enol. Vitic. vol.36 n.1 Stellenbosch. 2015.
  17. Conversation with Richard Preiss on MTF. 03/28/2016.
  18. Conversation with Richard Preiss on MTF. 02/15/2017.
  19. Conversation with James Sites about thiol producing wine strains on MTF. 08/19/2016.
  20. Wine yeast acclimation protocol for Escarpment Labs by Richard Preiss. 08/01/2016.
  21. 21.0 21.1 Tomme Arthur from the Lost Abbey on the Sour Hour
  22. Tonsmeire, Michael. American Sour Beer: Innovative Techniques for Mixed Fermentations. Brewers Publications. 06/15/2014. ISBN-13:9781938469138. Pg 271.
  23. Conversation with Bob Sylvester on his bottle conditioning methods on MTF. 09/26/2015.
  24. Brewers Friend's priming calculator.
  25. Discussion on MTF with Bob Sylvester, clarifying residual CO2 levels in his finished beer. 11/07/2016.
  26. 26.0 26.1 "Kathleen Round 3 - More Hops!" The Farmhouse Obsession Blog by Andrew "Gus" Addkison. 06/08/2016. Retrieved 06/08/2016.
  27. Bob Sylvester on rehydrating yeast and sugar together. Milk The Funk Facebook group. 12/13/2017.
  28. Bob Sylvester and Allen Stone. Milk The Funk Facebook group thread about keg conditioning and fill level. 10/26/2018.
  29. Don Million. Keg Your Beers! Brew Your Own Magazine. 2003.
  30. Keg conditioning thread on MTF with Bryan from Sui Generis and Devin Henry. 08/12/2016.
  31. Keg conditioning thread on MTF with Taylor John Caron. 11/07/2016.
  32. Jester King blog post about green bottles
  33. Jester King on the Sour Hour, pt 2
  34. Conversation between Pierre Tilquin and Dave Janssen, 24-Oct-2015
  35. Kemp, O., Hofmann, S., Braumann, I., Jensen, S., Fenton, A., and Oladokun, O. (2021) Changes in key hop-derived compounds and their impact on perceived dry-hop flavour in beers after storage at cold and ambient temperature. J. Inst. Brew.,
  36. Conversation with Chris Anderson on MTF. 9/22/2016.
  37. Rowan Chadwick. Milk The Funk Facebook group thread on bottle cleaners for small brewers. 04/25/2018.