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Jason Sledd's barrel and bulldog [1]

Barrels are wooden fermentation vessels which are an ideal vessel for fermenting many funky and mixed-fermentation beers. Many of the best mixed fermentation beers are aged in oak barrels or foeders. This page discusses the sorts of barrels and barrel alternatives available to pro and home brewers and influences those barrels have on the final beer to help brewers choose the barrel or barrel alternative that is right for them. In addition, this page gives some suggestions for using and taking care of barrels.

Types of Wood Used in Barrels

The type of wood used to make a barrel can impact both the flavor compounds that the barrel can provide as well as the rates at which gasses (O2) are allowed to penetrate through the wood. The characteristics of a given wood are dependent on the species used but also on factors such as more local conditions where the wood was grown in addition to the seasoning and toasting process. Toasting is discussed further in its own section below.


Acacia wood, also known as "Black Locust," is a species of tree native to the southeastern United States - although its roots have spread worldwide, from Europe all the way to Asia and as far south as Southern Africa. More recently, Acacia has been used as an alternative to the traditional white oak when aging White wine.

Although white wine is often aged in steel casks, wine makers have since discovered that aging in an Acacia barrel preserves the wines aromatic and fruit characteristics. Acacia wood does not contain as much tannin content as oak, thus, it better preserves freshness as well as floral and varietal characteristics. Additionally, white wines aged in Acacia barrels do not suffer from a loss of overall structure. Acacia wood is well suited for aging White wines as it does not contribute the stronger flavors one may find in oak, which may overwhelm a white wine, while stiff allowing a small amount of gas transfer.

American White Oak

American White Oak (Quercus alba) is regarded as one of the preeminent species of hardwood grown here in the United States of America. This species of White Oak has tyloses, an outgrowth of the parenchyma cells which stems from a reaction to natural stresses in the environment such as drought; which gives the wood a closed cellular structure, making it water- and rot- resistant. This closed structure also results in less air transfer through the wood than other oak types such as French oak.

Within the Wine & Spirits industry, Quercus Alba or American White Oak is the primary source of material in the production of Whiskey barrels (especially in the case of bourbon, which is legally required to be aged in charred new oak barrels). What makes this species of wood key to the whiskey industry is it chemical structure and the effect this imparts on the aging whiskey. American White Oak is known for its high vanillin content, oak lactone (coconut/bourbon characteristic), and wood sugars which all affect the bourbons taste. Additionally, American White Oak affects the coloring of the bourbon itself. Impure wood varieties like Pine contain resin canals which pass strong flavors into maturing whiskey. Note that the char levels in some spirits barrels might make them a less ideal candidate for many mixed-fermentation beers. In addition, some bourbon barrels are not constructed as sturdily as wine barrels [2], possibly due to the inability of producers to use barrels for many subsequent batches of bourbon (as would be common in wine).

French Oak

French oak (Quercus sessilis/Quercus petraea and Quercus robur) contributes comparatively more trans-3-Methyl-4-octanolide while American oak contributes more cis-3-Methyl-4-octanolide to beer.[3] These lactones both contribute a coconut character but the cis-lactone has a much lower flavor and aroma threshold,[4] therefore American oak barrels may give more of a lactone flavor and aroma impact. Q. sessilis is more common in wine aging and Q. robur is more common for cognac barrels.[3]

Hungarian Oak

(Quercus petraea, or commonly Sessile Oak.[5][6])

Romanian White Oak


Chestnut (Castanea sativa) can be a cheaper alternative to oak for barrels. Chestnut barrels are used by some lambic producers (though generally most lambic barrels are oak). Chestnut allows more gas permeability than oak, and therefore will allow more oxygen transfer than a comparable barrel made out of oak.[7]

Types of Barrels

(In progress)

Oxygen ingress will vary greatly even between the same type of barrels.[8]

Sherry Barrels

Sherry barrels typically have the most oxygen ingress.[8]

Spirit Barrels

Spirit barrels typically have less oxygen ingress than sherry barrels, but more than wine barrels. This also depends on the condition and char level of the spirit barrel.[8]

Wine Barrels

Wine barrels typically have less oxygen ingress than spirit and sherry barrels.[8] A standard 60 gallon Bordeux Chateau barrel weighs around 100 pounds (50 kg) empty, and about 600 pounds (275 kg) full.[9]

French wine barrels will have their hoops secured into place by nails. If the staves need to be tightened during swelling, then the nails must be removed. The nails can be removed with pliers or a hoop driver so that the hoops can be tightened. After tightening, the nails can be hammered back in, although some brewers just leave the nails out permanently. Justin Amaral recommends buying nails from Barrel Builders as they are reportedly easier to remove. [10]

  • Château Barrels (thin staves, recessed head, chestnut hoops, thin reed wrapped around the chestnut hoops on either side of the barrel head, a pine crossbar.)

Barrel Alternatives

in progress

A number of wood products are available to homebrewers to get wood characteristics without using a barrel. While barrel flavors are generally not the primary goal of funky beer brewers who use barrels for fermentation and aging, wood can contribute some of the additional characteristics that barrels offer (such as mouthfeel influences) and can also be used to house microbes in a similar way to a barrel (Vinnie's dimebags). The most common non-barrel wood products available to brewers are oak based. Advantages of using these products over barrels include reduced cost, ease of use, and a more efficient use of the wood (the entire surface of the wood is exposed to the beer as opposed to only 40% of a barrel's surface area) [11].

Chips - Oak chips maximize surface area and have less variability in the depth of toast. Oak chips are not ideal because if the brewer is after flavor contribution chips will be more one dimensional and if the brewer is not after a wood flavor contribution, oak chips will give faster flavor extraction than other options and will therefore not give the other benefits of oak as well as other products.

Cubes - Oak cubes are readily available to brewers. They offer greater toast complexity and a lower surface area to volume ratio than chips. (reference Vinnie's dimebags, amos oak in primary)

Rods - Rods offer a similar product to cubes however the surface area to volume ratio is even smaller. In addition, rods (and lumber) are the primary source for alternative woods. See John Gasparine's 2013 NHC presentation on alternative wood aging (AHA membership required).

Spirals - Wood spirals are basically rods that have been shaped to increase the surface area. They offer the same potential benefit as rods and cubes in dimension of toast flavor. Based on faster flavor extraction than rods, spirals may not be the ideal choice for brewers looking for the non-flavor benefits of wood.

Honeycombs - Honeycombs are similar to oak spirals in what they offer and they maximize the surface area even more.

Lumber Stores - Some woods traditionally used in barrels such as oak go through a prolonged curing process before being formed into a barrel and toasted. If you are trying to use one of these woods, be aware that just getting wood from a lumber store and toasting it yourself will not give the same results as properly cured woods used to make barrels and barrel alternative products. Lumber stores can be good resources for finding some 'exotic' non-traditional woods to use in their beers. For brewers interested in this we recommend this presentation from the 2013 National Homebrewers Conference given by John Gasparine (must be an AHA member to access). Note that some woods may contain compounds not safe for consumption so be careful and research your woods before you use them.

Patented Barrel Alternative Products

MTF Member Usage Suggestions

We'd love to hear your experiences! Please contribute them in this MTF Facebook thread.

Pre-treatments refers to anything the brewer might do with the barrel alternative before putting it in their beer (such as boiling, soaking in boiling water, soaking in wine or spirits etc.). Some brewers prefer pre-treatments to remove some of the more aggressive character of the wood and approach the sort of semi-neutralized barrel character that brewers might achieve from use of second hand wine or spirit barrels.

Wood Type Toast Level Format Amount Pre-treatment Contact Time Oak presence/Notes
American Oak Medium Toast Spirals 0.33*1x8" Spirals per gallon [12] None 6-12 months noticeable vanillin
American Oak Medium Plus Toast Spirals 0.33*1x8" Spirals per gallon [12] None 6-12 months noticeable vanillin
American Oak Medium Toast Cubes 0.4 oz per gallon [13] Boiled 11 months Could have used more oak. Note that the base beer was rather assertive.
French Oak Medium Toast Cubes 0.15-0.25 oz per gallon, depending on beer color/strength [14] Boiled Used cubes also re-used in 50-50 blends with fresh in subesquent batches
French Oak Bordeaux Blend (4 toast levels) Spirals 1.16" long spiral per gallon [15] None 1-3 weeks good tannin
French Oak Light Toast Spirals 1.16" long spiral per gallon [15] None 1-3 weeks Some structure, but otherwise not noticeable
Various Woods (Black Swan Barrel Alternatives) Honeycomb 1" long honeycomb per gallon [16] none 6 weeks May not be suitable for clean beers

Concrete/Clay Vessels

Alternative vessels include amphorea (also known as "Kvevri" in Georgian wine making [17]) and food-safe concrete vessels used in wine making.

Toast level and Volume

In progress

Barrels and barrel products are generally available in toast levels of light, medium, medium+ and heavy as well as varying levels of char. in addition to different wood types, different toast levels each have their own characteristics and are chosen for different purposes. Barrels used for aging spirits such as whiskey generally have some degree of charring, or at least heavy toast, while red wine barrels may be more commonly in the medium or med+ range. While the homebrewer and professional brewer does not always have full control over the toast levels of the barrels that they are getting (as the barrels are frequently used by wine and spirit producers before being acquired by brewers), brewers will likely find that different toast levels are better suited different beers.

Some brewers select specific barrels based on what they previously held as a fundamental component of certain beers (e.g. Russian River, Cantillon 50N, 3F Zenne). In addition, sometimes brewers aren't looking for barrel flavor in their sour beers and are more interested in the medium that barrels provide for fermentation in addition to some less flavor active compounds that barrels may contribute (--source: Jay and Tim Clifford for on the sour hour, probably something from JvR). Due to the delicate balance that good mixed-fermentation beers have, an aggressive barrel character may not always fit and brewers will have to get a feel for their barrels to know how long it takes for a beer to develop appropriate barrel character compared to how long until it develops the right fermentation character. For a first fill, it is recommended to taste the beer regularly to see how it is developing, and it may be necessary to allow additional aging in other vessels like carboys or stainless tanks for the beer to arrive at the right level of both fermentation development and barrel that the brewer is targeting.

---flavor description table to come (see also the flavor descriptions for different wood types above)----

Barrels are also available in a number of different volumes. Typical volumes of wine barrels are around 228L (60 gal) and may vary slightly depending on region and cooper. See this article for standard wine barrel sizes. See this article for a list of spirit barrel types and sizes. Professional breweries generally use barrels of this volume and larger.

For homebrewers, filling a barrel of such volume can be a bit more tricky and may require a group effort and/or many brews. Some smaller barrels are available for homebrewers via craft distillers and some specialty producers like Vadai. These barrels which can be found in the 5-15 gallon range provide an attractive option for homebrewers though some special considerations may be needed.

First, smaller volumes mean a greater surface area to volume ratio. This means that both flavor extraction from the barrel will be faster and O2 pickup will be greater (as oxygen penetration is tied to the barrel's surface area). Both of these factors make these small barrels attractive to craft distillers as they can shorten the aging time for certain flavor developments, but for the homebrewer looking to produce long-aged mixed-fermentation beers with no barrel flavor impact to supportive barrel character rather than strong barrel character, this is not ideal. The barrel character can be partially stripped by repeated use and soaking with water. One approach to this is to fill the barrel with hot water and allow it to cool overnight. The cooling will extract a lot out of the barrel, which can then be discarded. Because many of the small barrels available to homebrewers are derived from distilleries and therefore may be more likely a heavier toast level, it may take longer to remove the character of the wood and a progression of beers may be needed to make the barrel appropriately neutral for long aged sour beers [18]. Shortening the residency time of beer in smaller barrels can also reduce the effects of oxygen pick up (which results in acetic acid and ethyl acetate) and barrel wood character.

The environment in which smaller sized barrels are housed can play a role in how much oxygen enters the barrel. Temperature shifts within the barrel form a vacuum that causes air to get sucked in. In drier regions with low humidity, and regions that are hot and low in humidity (under ~30% on average), barrels can dry out and evaporate faster.

Second, the staves of smaller barrels are generally thinner allows greater oxygen permeability. So smaller barrels, both by surface area to volume ratio and by generally thinner staves, allow greater O2 transfer to the beer than larger barrels. Homebrewers may wish to counteract this O2 transfer by waxing smaller barrels [19], topping up regularly, keeping humidity around 40-50% and temperature as steady as possible, and aging for a shorter amount of time (1-3 months).

1-5 Liter Barrels

There are also various barrels on the market that are very small (1-5 liters). These barrels are designed as novelty items or perhaps aging spirits where oxygen exposure might not be as big of an issue as it is for beer (especially sour beer). The problems of a low volume and a high surface area expressed above are an even greater a threat when aging sour beer in such a small barrel. When Brettanomyces is exposed to oxygen, it produces acetic acid and small barrels can quickly produce too much acetic acid. Although aging for a very short amount of time in these very small barrels (perhaps 1 month or less) might produce favorable results, we recommend against aging sour beer in barrels that are smaller than 5 gallons (19 liters). Some people warn that the manufacturer of these small barrels uses very thin staves even for their larger version (20 liter). They are sold by a large number of outlets, and can be identified by their spigot and dot in the center of the head [20].

Using Barrels for fermentation and/or aging

in progress

How long should you wait to fill a new barrel? There are a few factors to consider here when deciding on how long to keep a barrel empty when first receiving it. For wine barrels, mold can develop inside if they are not cleaned out. Spirit barrels have less of a problem with mold due to the high ABV of the spirits. Another problem is barrels drying out. Many barrels are dry when they are received, and in that case, they need to be swelled before use (see Swelling Barrels). Spirit barrels might remain swelled from the spirits inside if the outside environment is humid enough, or if the brewer is occasionally spraying the barrels with water to keep them swollen. Storing them for too long (generally, more than a month is considered "too long" by brewers) might make the barrels dry out, and then when rehydrating them some of the spirit/wine characters will be lost during the hydration process. Filling the barrels as soon as possible is therefore preferred for preserving the spirit/wine character, but if the barrel dries out then they can often be swollen again successfully [21].

Should you top off or not? Yes (Tilqiun, Rare Barrel) No (Rare Barrel[22](~7 minutes in), Jester King[22](~7 minutes in), Crooked Stave, The Bruery). See also this MTF thread.

How long should you leave a beer in a barrel? The aging time will depend on what sort of beer you are making, what your desired outcomes are, and the characteristics your barrel gives. Belgian lambic is aged in barrels upwards of 4 years with no ill effects. Other beers can go through a barrel primary fermentation or very short aging and be out of the barrel in weeks to months. The longer you age a beer in a barrel, the more barrel character you will extract (in terms of both flavor and tannin structure). This is probably of secondary importance to how much the barrel has been used/how neutral it is, so keep your individual barrel characteristics in mind when determining aging time. Generally, producers of mixed fermentation beers do not report noticing problems from autolysis in prolonged aging on yeast sediment [22](~9 minutes in).

Andy Parker from Avery Brewing Co., in discussing non-sour beer in barrels, says that they get a complete extraction of flavor from barrels within 2 months. After four months, effects from oxidation can be detected, and after twelve months the more porous barrels display heavier effects from oxidation. Parker recommends removing the beer from a barrel based on the effects of the oxidation of individual barrels (in sour beer, this could have an affect on the perception of acetic acid and ethyl acetate, as well as other oxidative characteristics such as sherry notes, depending on the style of the beer) [23]. Sour beer generally takes longer to mature in barrels due to the microbial activity, however this advice might still apply to sour beers in certain barrels that are experiencing too much or very fast oxidation due to being more porous than other barrels.

What environmental conditions should barrels be aged in? Generally, a humidity level of 40-60% is desirable. This helps decrease the evaporation rate, which helps reduce the amount of oxygen the beer is exposed to. Temperatures should be as stable as possible, however, temperature fluctuations sometimes cannot be avoided, and seasonal changes are thought to be an important part of the extended fermentation of beers such as Belgian Lambic. Some brewers have reported success with daily temperature swings and hot temperatures above 90°F [24][25].

Should you clean your barrel after every use? Jester King reports preferring barrels that get a bit more yeast in them (when using barrels as secondary vessels) and they may use barrels for 2-3 subsequent beers before rinsing out the trub [22](~9 minutes in, ~16 minutes in).

Controlling Oxygen

Controlling Mold in Humid Climates

Modifying barrels

Barrels can be modified to operate as tanks such as mash tuns and/or fruiting vessels:

Temperature Control

Fruit Flies

Preventing Mildew

Barrel Care


Swelling barrels

Swelling barrels involves soaking the heads and/or staves of a barrel with water to cause them to swell up and form a tight seal. If a barrel has been stored dry, it might be necessary to swell the barrel, or at least leak test it, before filling it with beer. In general, using steam to swell barrels is preferred over water because it strips less character away from the oak. There are many approaches to swelling barrels. For example, The Rare Barrel swells barrels in a couple of different ways. When they are not worried about preserving the character of what was previously held in the barrel, they fill the barrels with water without storage chemicals for a maximum of 48 hours before changing water if the barrel is not fully swollen [28] (~33 minutes in).---To do--- external swelling (ref rare barrel, Tilquin head swelling, Todd Ashman Eclipse).
External swelling can be done by placing a barrel on its head and cover the upward facing head with hot water for several hours. Flip the barrel on its other head and repeat. This process swells the heads which in turn pushes the staves tighter together in the hoops.
Although impractical for homebrewers, commercial brewers and winemakers can use steam to swell barrels (although wallpaper steamers are a good option for homebrewers) [29]. Steamed barrels should be allowed to cool before bunging; cooling with a bung installed can lead to imploding barrels [30]. Steaming can also be a technique for cleaning used barrels.

Large oak casks that are larger than normal wine/bourbon barrels are sometimes sealed with wax by the manufacturer or a cooper. Some coopers recommend to swell large casks using only cold water so that the wax that is between the staves does not melt [31]

Swelling With Steam

Below is a general process for steaming barrels provided by Johnny Horn:

  1. Tighten staves by hammering the hoops towards the bilge.
  2. Swell barrel with cold water (boiling water if possible) to check for leaks.
  3. Steam for at least 30 mins.
  4. Swell with water to check for leaks again.
  5. Rinse, repeat.

Swelling Without Steam

Andrew Zinn's method:

  1. Tighten the hoops.
  2. Pump hot water in through a spray ball until it’s about 2” deep.
  3. Hard bung the barrel, and rotate ~75° every 10-15 minutes.
  4. If the bung has pulled a vacuum by the time it’s on its 5th rotation, the barrel is ready to rinse, purge with CO2, and fill with beer or wort.


Steam or hot water can be used to clean out barrels. See Steamers and Cleaning Stations below. Cleaning chemicals are often avoided by many brewers, although Barrel Builders includes instructions for using chemical cleaners such as sodium percarbonate products like Proxycarb™, Acto 140™, Leraspet SPO, or soda ash, followed by a citric acid wash. A product called "Barolkleen" is also available and should be followed up with a citric acid wash. See this MTF thread for more information. It is advised not to use water that contains chlorine or chloramine to clean barrels. The residual chlorine or chloramine may not be enough to impact flavor directly once emptied from the barrel, but these chemicals form hypochlorite [32] [33], which is one of the two things needed to cause 2,4,6-trichloroanisole (TCA). The second thing needed to produce TCA is mold. TCA is a common off-flavor in the wine world, and is described as "moldy, musty, cork taint" [34].

Some producers remove heads from barrels during cleaning. This may be beneficial if whole fruit is used in the barrel [35]

MTF barrel cleaning threads:


Heat has been established as the most reliable way to sanitize surfaces, with Brettanomyces beginning to die at around 37°C [37][38]. The complete thermal death of Brettanomyces in wines has been reported to be accomplished at 50°C for 5 minutes. [39][38]. Sanitizing barrels that are infected with Brettanomyces or other beer/wine spoilers is notoriously difficult, and some believe it to be impossible. While two previous studies (Schmid et al. 2011 and Barata et al. 2013) found that steam was not effective at sanitizing oak, these studies have had their experimental designs criticized by more recent studies (Fabrizio et al. 2015 and Cartwright et al. 2018). For example, Schmid et al. (2011) inoculated oak chips with nutrient broth instead of using barrels that represented real-world conditions, and Barata et al. (2013) only applied steam for 10 minutes [40].

In contrast, Fabrizio et al. (2015) and Cartwright et al. (2018) found that it is possible that steam is an effective way to kill all Brettanomyces in oak barrels that previously held B. bruxellensis inoculated wine. Fabrizio et al. (2015) proposed that the most effective and preferred method is to heat the inside of the oak barrel to at least 140°F (60°C) for 20 minutes with hot water or steam. This was demonstrated to be an effective way of killing Brettanomyces that was found growing as deep as 8 mm within the wood of 3-year old barrels infected with Brettanomyces. Note that this might not be hot enough to kill other heat-tolerant microbes; however, these heat-tolerant species tend not to be able to survive in beer. Steam treatments that are higher in temperature and longer should not present any concerns to the barrels themselves; however, if hot water is used instead of steam then the longer the water is exposed to the barrel the more character from the barrel that gets removed by the water [41][42].

Cartwright et al. (2018) confirmed these results and reported that as little as 12 minutes of steam was enough to eliminate Brettanomyces in both French and American oak wine barrels that were previously inoculated with B. bruxellensis for 6 to 7 months. In general, the French oak barrels had larger populations of B. bruxellensis than the American oak barrels, likely due to American oak being less dense. The staves closest to the bungholes had the largest population of B. bruxellensis 0-4mm into the wood, likely due to better access to oxygen, but there were also large populations within the bottom staves which were found at deeper levels into the wood (5-9mm deep). Oak barrels with heavy toast levels tended to have higher populations perhaps due to more cracks in the staves or more availability of cellobiose. The French barrels required 12 minutes and the American oak barrels required only 9 minutes at 131°F (55°C) to eliminate all B. bruxellensis from even the deepest points into the oak where B. bruxellensis has been found (up to 9mm). Before this was achieved, it took 4 minutes to reach this temperature at 9.5mm into the oak. They could not culture Brettanomyces from the oak even after incubation of stave cross-sections in WRM for 60 days. Hot water was also reported by the same research group to effectively eliminate Brettanomyces from oak barrels, although it took longer (70°C for 30 minutes or 80°C for 20 minutes). The researchers expressed the opinion that the effect of heat treatment on barrel quality needs to be researched. Although it has been reported that extensive heating can destroy desirable oak flavor compounds such as guaiacol, 4-methylguiaicol, furfural, lactones, eugenol, and vanillin, degradation of these compounds requires temperatures between 248°F (120°C) and 365°F (185°C) for 1 to 6 hours, so significant degradation of desirable oak flavor compounds is not expected to occur with 12 to 20 minutes of 131°F (55°C) to 140°F (60°C) of steam pasteurization [40][43][44].

Swaffield and Scott (1995) found that the lactic acid bacteria belonging to the genre Lactobacillus, Pediococcus, and Leuconostoc that were in cider penetrated oak blocks up to 1.25 cm after 9 weeks of being submerged 1 mm into the cider, so it is possible that bacteria can grow deeper than 8 mm into oak, although these oak cubes were made from virgin oak vats and might not accurately reflect what would be found if these same microbes were inoculated in oak barrels [45]. Additionally, some strains of Lactobacillus can survive higher temperatures than Brettanomyces can; see Lactobacillus for more information. Other yeast species may also be more resistant to heat sanitation in barrels. Specifically, Debaryomyces hansenii, Candida parapsilosis, Candida ishiwadae have been found to be more resistant to steam treatment in wine barrels than B. bruxellensis [46].

Ozone has been shown to be an effective way to kill Brettanomyces that is buried in the wood of oak barrels (it has been found to burrow as deeply as 8 mm into oak barrels), but the ozone must be applied for an adequate time to allow for the ozone to diffuse into the oak. The amount of time needed to completely kill Brettanomyces living within barrels with ozone is not known, but it was found that 30 minutes of exposure to 40 mg/m3 ozone concentration was not enough time and the presence of organic material interferes with the ozone's ability to kill [47]. The concentration of ozone is known to be a more important killing factor than time, therefore some recommend filling the barrel with liquid ozone, or rinsing with hot water first to open the pores of the wood and then rinsing with ozone liquid [48][49].

Other non-thermal methods of pasteurizing barrels have been explored. Microwave treatment at 3000 W for 3 minutes of barrels filled with water reduced populations by 35% in French oak barrels and 67% in American oak barrels up to the 8 mm depth in which Brettanomyces can survive within the wood of oak barrels. High power ultrasonics (17 W/L for 3 minutes) applied to barrels filled with 60°C water kills all Brettanomyces up to 4 mm within the oak, but has limited penetration of the wood passed 4 mm [40]. The use of sulfur dioxide (SO2) has been shown to inhibit Brettanomyces and other microbes; however, Brettanomyces cells that are exposed to sulfur dioxide can enter a state known as "viable but nonculturable" (VBNC) meaning that they cannot complete cell division (grow) but can still maintain a small amount of metabolism, and can be revived when the sulfur dioxide is no longer in their environment. Therefore, sulfur dioxide is not an effective way to completely sanitize oak barrels (although it has been used successfully to store non-infected barrels). See VBNC in Yeast for more information.

Other sanitizers such as StarSan or iodine should be avoided due to absorption of chemicals into the wood.

See also:


Storing Empty

Previously, some brewers have advised filling empty barrels with storage solution, burning sulfur sticks, or filling with ozone. However, recent trends with commercial brewers are to store barrels completely empty and then steam them to swell them and tighten the hoops before use. Some brewers have reported residual sulfur flavors when stored with a sulfur solution. Also, after storing a barrel with a sulfur solution, it needs to be steamed for an extended amount of time to remove the sulfur, so since the steaming process will be employed either way many brewers don't see the need to store with a sulfur solution. Some brewers have reported difficulty rinsing barrels properly when they are pyramid stacked and cannot be moved. Other brewers have had no problem removing the sulfur from barrels that were stored with a sulfur storage solution, and some suggest that small amounts of sulfur will help protect the beer from oxidation. Additionally, storing barrels with a sulfur solution ensures that mold growth does not become an issue. Still, other brewers recommend storing barrels empty for only 2 or 4 weeks (some brewers recommend burning a sulfur stick during the initial empty storage time, others store completely empty), but after that, they should be filled with a sulfur solution or ozone [50].

Burning sulfur sticks/wicks or disks: for the preservation of empty barrels or other wooden vessels, burn 4 g of sulfur per hectoliter of capacity and repeat every 40 - 50 days [51]. To use disks, use a disk holder (e.g. GW Kent sulfur disk holder or create a wire hook to suspend the sulfur disc in the barrel. Light the disc and place into the barrel, inserting a bung to prevent the SO2 gas from escaping. Leave to burn for a few minutes before removing and bunging the barrel for storage.

Note: Do not burn sulfur in used spirit barrels, as there is a risk of explosion. Once a spirit barrel has had a beer aged in it, the ethanol levels within the barrel won't be high enough to cause an explosion. The general rule of thumb is if the spirit can be smelled inside the barrel, don't light a sulfur disc in it.

Storing full

Sulfur Storage Solution Method:

Barrels can be stored full with a solution of water, potassium metabisulfite, and citric acid. The citric acid is used to lower the pH which is necessary to make the potassium metabisulfite antimicrobial (see this Cornell University blog post).

A storage solution of 1 g citric acid and 2 g potassium metabisulfite per L (or 1 lb potassium metabisulfite and 0.5 lb citric acid per 225 L barrel[52] (~40 min in)) is often used.

Update: The lined out instructions above have sometimes been advised by winemakers, and presumably taken from their instructions [53]. Jay Goodwin from The Rare Barrel; however, reported sulfur off-flavors in beers from using too much potassium metabisulfite in their barrels. The beers needed extended aging for the sulfur to be volatilized off. Eric Salazar from New Belgium Brewing advised that they cut the potassium metabisulfite powder down to 1 ounce per 59 gallon barrel (~0.017 ounces per gallon/~0.127 grams per liter) [54], and to check the barrel once a month and change the storage solution once a month if needed [55][56]. The amount of citric acid is the same: 0.5 lb per 59 gallon barrel (1 gram per liter/0.13 ounces per gallon) [56]. Before using a barrel holding this sort of storage solution, the barrel should be intensely sprayed and rinsed (not just filled up with hot water and dumped). Steaming the barrel before hand can also reduce microbial populations (see Sanitizing Barrels above).

Andrew Zinn from Wicked Weed reported that the recommendation above was not enough potassium metabisulfite to prevent microbial growth. They found that 0.3 grams of potassium metabisulfite per liter was the best balance between inhibiting microbial growth while limiting residual sulfur aromas in the barrel. Barrels with this holding solution have been reportedly free of microbial growth for 6+ months. Barrels are only filled with holding solution if they are going to sit for longer than a month; anything earlier than that is sulfured by burning an SO2 tab [57]. They also found that first rinsing the sediment out of barrels with cold water briefly before rinsing with hot water or steaming helps remove residual sulfur [58].

This method is not recommended by some brewers due to the residual sulfur that can be difficult to rinse from the barrel, and the over-extraction of the barrel's flavor compounds into the storage soltuion.

Ozone Method: [59] [need to expand]

Used for sanitation. A separate cleaning procedure is needed separately from using ozone to sanitize.

Moving To New Facility

At times brewers are faced with the challenge of moving barrels full of beer to a new facility. Some brewers recommend emptying the barrels into totes and purging the head space with CO2. Others recommend using a forklift to carefully move the barrels still on racks into the moving vehicle, and gently drive the barrels to the new location. Once the barrels are set in place at the new facility, purge the headspace of the barrels with CO2. Moving full barrels can be risky to the beer by introducing oxygen and potentially unsafe to workers. Use caution. See also this MTF thread.

Maintenance and Repairs

132 gallon Oloroso Sherry cask with a broken ring. Image provided by Raf Soef.

Misc Info

  • Barrels can be stored upright and used to add fruit to beer. A "punch-down" (punch down) process can be used to gently push the fruit under the surface of the beer to make sure it has contact within the beer, that CO2 is released, and that mold does not form. See "Punch Down Beer", blog article on Funk Factory Guezeria on fruiting in an upright barrel and punching down fruit.
  • Barrels used by some lambic producers (notably 3 Fonteinen and De Cam) were originally 4000 liter barrels used by breweries like Pilsner Urquell. The barrels used for lager brewing are pitched. However, they were rebuilt to hold 1000 liters, and the pitch was removed before being sent to lambic brewers in Pajottenland [61][62].
  • Potassium bitartrate (KHTa) is formed in wine, through the reaction between the bitartrate ion (HTa-), from tartaric acid (H2Ta), and the potassium ion (K+) found in grapes, especially grape skins. It is also known as potassium hydrogen tartrate, and commonly called "Cream of Tartar", "wine crystals", potassium salt of tartaric acid, tartrates, argols, tartres (French), Weinstein (German - "wine stones") [63][64]. KHTa build up appears as crystals in wine barrels. It has no affect on the taste of wine, and is assumed to have no affect on the taste of beer [65][66], however heavy build up of wine crystals can pose a problem [67]. They can be removed from the inside surface of barrels through cleaning with Proxycarb™ or another sodium percarbonate based cleaner such as scent-free Oxyclean™ (see the Barrel Builders Barrel Maintenance Repair Manual).
  • Over sulfuring of sour beer is a somewhat common problem. It often results from using too much sulfur to store in a barrel. Sulfur can also be the result of fermentation. Additional time will eventually allow the sulfur to age out. Other recommendations include running the beer through a food safe copper pipe, purging the beer with CO2, using a wine product called Redules, or even simply transferring the beer from one vessel to another (the small amount of oxygen pick up combined with yeast activity will typically reduce the sulfur).

Room/Drain Layouts

MTF Threads:

Management Software


Innerstaves are extra wood planks that are inserted into a barrel by a cooper to add more wood flavor to wine. Some brewers recommend removing them or asking their barrel broker not to sell them barrels with innerstaves. See also this MTF thread for an example and advice.

General Resources and Articles

General Cooperage

Maintenance and Repairs

Racking Canes

Steamers and Cleaners

Pyramid Stacking and Barrel Taps

Pyramid stacking is a semi-permanent structure of barrels that are stacked upon each other with wood wedges to secure their location. Barrels are first stacked empty, and once filled they do not move. The head is often drilled with a 15/16th drill bit near the bottom of the barrel when lying horizontally, and plugged with a standard champagne cork. To empty the barrel, the champagne cork is removed and a barrel tap is inserted into the hole to rack the beer. This method requires less space horizontally than using barrel racks and avoids the cost of barrel racks, however, if a barrel on a bottom row needs to be removed then all of the barrels above it also need to be emptied and moved. Mobility of barrels is therefore sacrificed for space and cheaper cost. Another benefit of pyramid stacking is that a forklift is not required. See also Andrew Zinn's list of benefits to pyramid stacking.

Barrel Tap Manufacturers:

Informational MTF posts:

Porn Tap Parts List

  1. Barrel Tap
  2. 1/2" NPT threaded tri-clamp fitting
  3. Valve of some sort (this is what Jeff uses)
  4. Tr Clover Clamp and seal

In the end, you can really decide what you want to put on the end of the tap, the threads are 1/2" NPT. Jeff Porn demos the barrel tap here.


One way ventillation silicone bungs are generally recommended for long aging sour beers in barrels (after primary fermentation) [78].



Waxing Small Barrels

Embrace The Funk Tips

Vinnie Nail

Steps [79]:

  1. When the barrel is full of beer and with a bung in the bunghole to prevent extra spillage, drill a hole using a 7/64 drill bit in the middle of the barrel head. Try not to drill all the way in to avoid mess [80]
  2. Quickly but gently hammer in the 1-1/2" nail the rest of the way. Metric users: substitute nail for a 3mm width by 30mm length nail, and a 3mm drill bit (smaller diameters might not pour well) [81]
  3. Wax around the nail if it keeps weeping.
  4. Choose a tool to remove the nail with. Popular recommendations are: channellock pliers, 9" side cutting pliers, small pry bar, traditional "curved claw" hammer, vice grips [82].
  5. To pull a sample, remove the nail with the chosen tool (remove the bung/airlock as well if there is not enough pressure), take a sample, and then hammer in the nail again. Optional: to avoid messes, remove the nail most of the way with the tool, and then put the tool down and pick up a glass, and remove the mail the rest of the way with your free hand [83].
  6. Keep 2" steel nails handy in case the hole in the barrel head starts to get too big.


General Barrel Aging Information


Milk The Funk Tips and Discussions

Sourcing Barrels - Manufacturers and Suppliers

Pro Sizes

Offers Smaller Sizes

Used Homebrew Sized Used Barrels

Scam Websites

These are sites that have been reported by MTF members as being scam websites pretending to sell oak barrels. We recommend that you do not buy anything from them nor visit their website.

  • This website is a scam; do not purchase barrels from them [87]. See this MTF thread.
  • This website is a scam; do not purchase barrels from them. See this MTF thread.

See Also

Additional Articles on MTF Wiki

External Resources


  1. Conversation with Jason Sledd on Milk The Funk. 05/03/2015.
  2. MTF discussion about bourbon barrels
  3. 3.0 3.1 Review of quality factors on wine ageing in oak barrels. Garde-Cerdan and Ancin-Azpilicueta (2006)
  4. Effect of oak barrel type on the volatile composition of wine: Storage time optimization. Garde-Cerdan and Ancin-Azpilicueta (2006)
  5. Quercus petraea. Wikipedia. Retrieved 06/16/2018.
  6. Brandon Jones. Private correspondence with Dan Pixley. 06/16/2018.
  7. Effect of aging in new oak, one-year-used oak, chestnut barrels and bottle on color, phenolics and gustative profile of three monovarietal red wines. Gambuti et al., 2010
  8. 8.0 8.1 8.2 8.3 Justin Amaral. Milk the Funk Facebook post on measuring oxygen in barrels. 02/15/2018.
  9. Julien Miguel. "Anatomy of a Wine Barrel: Parts, Sizes, Infographic". Social Vignerons website. 06/27/2016. Retrieved 07/31/2018.
  10. Joseph Kearns, Justin Amaral, and Andrew Zinn. MTF thread about tightening hoops on French oak barrels. 01/23/2018.
  11. Influence of oak chips addition on the physicochemical properties of beer. Monika Cioch‑Skoneczny, Mateusz Bajerski, Krystian Klimczak, Paweł Satora, Szymon Skoneczny. European Food Research and Technology. 2022.
  12. 12.0 12.1 Milk the Funk Facebook Oak discussion
  13. Milk the Funk Facebook member brew CC
  14. Milk the Funk Facebook Oak discussion
  15. 15.0 15.1 Milk the Funk Facebook Oak discussion
  16. Milk the Funk Facebook Oak discussion
  17. "Kvevri". Wikipedia. Retrieved 11/13/2020.
  18. Basic Brewing Radio barrel progression
  19. Funk Factory Barrel Waxing
  20. James Shamas. Milk The Funk Facebook group. 07/13/2017.
  21. Various MTF Members. MTF thread about how long to wait to fill a new spirit barrel. 11/16/2017.]
  22. 22.0 22.1 22.2 22.3 Jester King on the Sour Hour part 2
  23. "5 Tips on Barrel Aging from Avery Brewing Co." Andy Parker on the AHA website. Retrieved 05/10/2016.
  24. Various MTF members. Milk The Funk Facebook thread about Aardwolf Brewing Company in Jacksonville started by Derek Springer. 07/07/2017.
  25. Brandon Jones. Milk The Funk Facebook group thread on hotter temperatures for barrel rooms. 04/15/2018.
  26. Matthew Fields. Milk The Funk Facebook group post on wine barrel triclamp taps & manways from Glacier tanks. 02/16/2018.
  27. Milk The Funk Facebook group thread on how to seal the bung in a barrel. 05/02/2019.
  28. The Sour Hour Episode 16
  29. Barrel Steam Wand
  30. Conversation about steaming barrels and bunging on MTF. 05/31/2017.
  31. Joshua Martinez and Levi Funk. Milk The Funk Facebook group thread on swelling large casks with cold water. 06/13/2018.
  32. "Chloramine". Wikipedia. Retrieved 09/14/2016.
  33. "Chlorine". Wikipedia. 09/14/2016.
  34. "Chlorine Use in the Winery". Christian Butzke. Purdue University. Retrieved 09/14/2016.
  35. Crooked Stave facebook post 2-Nov-2015
  36. Conversation about steaming barrels and bunging on MTF. 05/31/2017.
  37. Thermal inactivation of the wine spoilage yeasts Dekkera/Brettanomyces. José António Couto, Filipe Neves, Francisco Campos, Tim Hogg. 2005. DOI: 10.1016/j.ijfoodmicro.2005.03.014.
  38. 38.0 38.1 Survival and metabolism of hydroxycinnamic acids by Dekkera bruxellensis in monovarietal wines. Adriana Nunes de Lima, Rui Magalhães, Francisco Manuel Campos, José António Couto. 2020. DOI:
  39. Thermal inactivation of the wine spoilage yeasts Dekkera/Brettanomyces. José António Couto, Filipe Neves, Francisco Campos, Tim Hogg. 2005. DOI: 10.1016/j.ijfoodmicro.2005.03.014.
  40. 40.0 40.1 40.2 Reduction of Brettanomyces bruxellensis Populations from Oak Barrel Staves Using Steam. Zachary M. Cartwright, Dean A. Glawe, Charles G. Edwards. 2018. DOI: 10.5344/ajev.2018.18024.
  41. Heat inactivation of wine spoilage yeast Dekkera bruxellensis by hot water treatment. Fabrizio, Vigentini, Parisi, Picozzi, Compagno, Foschino. 2015.
  42. Brettanomyces bruxellensis yeasts: impact on wine and winemaking. Monica Agnolucci, Antonio Tirelli, Luca Cocolin, Annita Toffanin. 2017.
  43. Zachary Cartwright and Charles Edwards. "Wine maturation: What can a winemaker do about 'Brettanomyces bruxellensis' present in oak barrels?" Wine & Viticulture Journal. Volume 34 Issue 4 (Spring 2019).
  44. Edwards, C.G. and Cartwright, Z.M. (2019) Applicatio nof heated water to reduce populations of Brettanomyces bruxellensis present in oak barrel staves. Sth. Afr. J. Enol. Vitic. 40:1-8.
  45. Existence and Development of Natural Microbial Populations in Wooden Storage Vats Used for Alcoholic Cider Maturation. C. H. Swaffield and J. A. Scott. 1995. DOI: 10.1094/ASBCJ-53-0117.
  46. Guzzon, R., Widmann, G., Malacarne, M. et al. Survey of the yeast population inside wine barrels and the effects of certain techniques in preventing microbiological spoilage. Eur Food Res Technol 233, 285–291 (2011).
  47. Survey of the yeast population inside wine barrels and the effects of certain techniques in preventing microbiological spoilage. Guzzon, Raffaele & Widmann, Giacomo & Malacarne, Mario & Nardin, Tiziana & Nicolini, Giorgio & Larcher, Roberto. 2011.
  48. Nate Ferguson of Escarpment Labs. Milk The Funk Facebook thread about using ozone to sanitize barrels. 10/24/2017.
  49. Wines & Vines website. "Barrel-Washing Protocols". Jan 2013. retrieved 10/24/2017.
  50. MTF poll and various MTF members on storing barrels empty vs full. Milk The Funk Facebook group. 11/17/2017.
  51. 2016. Laffort sulfur disc instruction manual. South Africa
  52. The Sour Hour with Tim Clifford of Sante Adairius
  53. M&M Wine Grape Co. Citric Acid & Sulfite Barrel Preparation. Retrieved 03/06/2016.
  54. Mike Makris. Milk The Funk Facebook group. 04/12/2017.
  55. The Sour Hour Episode 28 (~49 minutes in). Jay Goodwin from The Rare Barrel. 02/17/2016
  56. 56.0 56.1 Private correspondence with Mike Makris from The Rare Barrel by Dan Pixley when asked to clarify the amounts that Eric from NBB recommended. 03/06/2016.
  57. Andrew Zinn. Milk The Funk Facebook group. 05/19/2017.
  58. Andrew Zinn on rinsing barrels with cold water first. Milk The Funk Facebook post. 11/18/2017.
  59. Ozone sanitation for barrels
  60. Brandon Jones. Milk The Funk Facebook group thread on repairing a crack in a foeder. 11/17/2018.
  61. Lambicland by Webb, Pollard and McGinn (2010)
  62. Conversation with Gareth Young and Raf Soef on MTF regarding lambic barrels. 09/22/2015.
  63. Wikipedia. Potassium bitartrate. Retrieved 09/30/2015.
  64. Monash Scientific. Potassium bitartrate. Retrieved 09/30/2015.
  65. Conversation in Milk The Funk about tartrates. 09/30/2015.
  66. UNDERSTANDING WINE TARTRATES. Jordan Winery. Retrieved 09/30/2015.
  67. Brandon Jones. Milk The Funk facebook comment on wine crystals. 10/10/2017.
  68. The Sour Hour Podcast, Episode 39, ~56 minutes in. Jay Goodwin. Retrieved 08/06/2016.
  69. Anthony Baraff. Milk The Funk Facebook thread on bulldogs in Europe. 04/17/2019.
  70. Brandon Jones. Milk The Funk Facebook group. 07/11/2017.
  71. Sean McVeigh on GW Kent steamer. Milk The Funk Facebook group. 11/1/2017.
  72. MTF conversation with Brandon Fender regarding cleaning barrels. 08/31/2016.
  73. Steamer recommendation from Gregory Wilhelm on MTF. 09/06/2016.
  74. Conversation with Cameron Pryor on steam cleaners on MTF. 11/20/2016.
  75. Conversation 1 with Cameron Pryor on MTF about a barrel steaming station. 11/20/2016.
  76. Conversation 2 with Cameron Pryor on MTF about a barrel steaming station. 11/20/2016.
  77. Tristan Stewart. Milk The Funk Facebook thread on Tristan's brewery and racking wand for pyramid stacked barrels. 02/07/2018.
  78. Question on MTF regarding what type of bung/airlock. 12/24/2016.
  79. Quoted email from Vinnie Cilurzo on the Burgundian Babble Belt forum. Retrieved 12/1/2016.
  80. Andrew Zinn on MTF. Drilling a Vinnie Nail. 08/29/2017.
  81. Mattias Terpstra on MTF. Vinnie Nail diameter for metric. 08/29/2017.
  82. Various MTF members. Tools for removing a Vinnie Nail. 08/29/2017.
  83. Sean McVeigh on MTF. Removing a Vinnie Nail without making a mess. 08/29/2017.
  84. Matt Warren. Milk The Funk Facebook group post. 10/05/2016.
  85. Private correspondence with The Oak Cooperage by Caleb Buck. 02/13/2017.
  86. Conversation with Ryan Sealey on MTF regarding Wine Oak Barrels . 01/29/2017.
  87. "SCAM ALERT: Fake bourbon barrel company deceives customers". Chris Chandler. WLKY newspaper website. 12/21/2018.