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.
- 1 Types of Wood Used in Barrels
- 2 Types of Barrels
- 3 Barrel Alternatives
- 4 Toast level and Volume
- 5 Using Barrels for fermentation and/or aging
- 6 Barrel Care
- 7 Misc Info
- 8 General Resources and Articles
- 8.1 General Cooperage
- 8.2 Maintenance and Repairs
- 8.3 Racking Canes
- 8.4 Steamers and Cleaners
- 8.5 Pyramid Stacking and Barrel Taps
- 8.6 Bungs
- 8.7 Waxing Small Barrels
- 8.8 Embrace The Funk Tips
- 8.9 Vinnie Nail
- 8.10 Racks
- 8.11 General Barrel Aging Information
- 8.12 Pumps
- 8.13 Milk The Funk Tips and Discussions
- 9 Sourcing Barrels - Manufacturers and Suppliers
- 10 See Also
- 11 References
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 , possibly due to the inability of producers to use barrels for many subsequent batches of bourbon (as would be common in wine).
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 . These lactones both contribute a coconut character but the cis-lactone has a much lower flavor and aroma threshold , 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 
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
Types of Barrels
Oxygen ingress will vary greatly even between the same type of barrels .
Sherry barrels typically have the most oxygen ingress .
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 .
Wine barrels typically have less oxygen ingress than spirit and sherry barrels . A standard 60 gallon Bordeux Chateau barrel weighs around 100 pounds (50 kg) empty, and about 600 pounds (275 kg) full .
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 .
- 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.)
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.
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
- The Squarrel Barrel.
- Titan Barrel Works "titan Barrel". See also this MTF thread.
- Inner Stave 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 ||None||6-12 months||noticeable vanillin|
|American Oak||Medium Plus Toast||Spirals||0.33*1x8" Spirals per gallon ||None||6-12 months||noticeable vanillin|
|American Oak||Medium Toast||Cubes||0.4 oz per gallon ||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 ||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 ||None||1-3 weeks||good tannin|
|French Oak||Light Toast||Spirals||1.16" long spiral per gallon ||None||1-3 weeks||Some structure, but otherwise not noticeable|
|Various Woods (Black Swan Barrel Alternatives)||Honeycomb||1" long honeycomb per gallon ||none||6 weeks||May not be suitable for clean beers|
- See also Jeffrey Crane's guide to oak aging alternatives: part 1, part 2, and the other parts Jeff will never finish.
- Tips on MTF on soaking oak chips/cubes/spirals in wine.
- Tips on MTF on using wood other than oak.
- "Oak Alternatives" by Tim Vandergrift in Wine Maker Magazine.
- "Oak Varieties and Shapes: A Comprehensive Overview" by Cat Stewart on HBT.
Alternative vessels include amphorea and food-safe concrete vessels used in wine making.
- See Concrete Beer Tanks and this MTF thread.
- MTF amphora thread and this MTF thread and this MTF thread.
- Alex Seitz from VonSeitz Theoreticales explains the amphora building process, and discusses a gruit made with Mud King and amaranth.
- Another MTF thread on using Terra-cotta pieces to age in another vessel, as well as success/failures on aging in amphorae above/below ground.
- Using other types of stones/rocks in beer to gain minerality.
- Qvevri Project (amphorea manufacturer).
- "Preparing Our Qvevri: Coating the Interior with Beeswax", Wine Trail Traveler blog.
- Amphorea/Clay Cooking Pot Videos:
Toast level and Volume
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 .
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, 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 , 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 .
Using Barrels for fermentation and/or aging
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 .
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 (~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) . 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 .
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 (~9 minutes in, ~16 minutes in).
Barrels can be modified to operate as tanks such as mash tuns and/or fruiting vessels:
- Casey, Ale Apothecary, Ethan Protas MTF Thread
- Levi Funk thread, with tips from Tilquin.
- Funk Factory Brewing modified barrel for aging beer on fruit. Associated MTF thread here.
- Glacier Tanks custom manways for barrels and puncheons. See also Glacier Tanks LLC sells a manway fitting for barrels. 
- A different implementation of the Glacier Tank produce by Rusty Abernathy on MTF.
- Vertically stored barrels can have their bung sealed by using a silicon bung, rubber bung, or wooden bung .
- Homebrewer Samuel Neitzke's modification of small barrels for a CO2 post and a sample port for easy transfers and CO2 purging.
- MTF thread on dealing with fruit flies, and fitting blow off tubes.
- MTF thread on dealing with fruit flies in general (specifically during open fermentation, but applies everywhere else too).
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  (~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) . Steamed barrels should be allowed to cool before bunging; cooling with a bung installed can lead to imploding barrels . 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 
Swelling With Steam
Below is a general process for steaming barrels provided by Johnny Horn:
- Tighten staves by hammering the hoops towards the bilge.
- Swell barrel with cold water (boiling water if possible) to check for leaks.
- Steam for at least 30 mins.
- Swell with water to check for leaks again.
- Rinse, repeat.
Swelling Without Steam
- Tighten the hoops.
- Pump hot water in through a spray ball until it’s about 2” deep.
- Hard bung the barrel, and rotate ~75° every 10-15 minutes.
- 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.
- See also Barrel Builders Barrel Maintenance Repair Manual, Section 2.3 (using SO2 for soaking more than 2 days).
- See also Vadai Barrel Prep Instructions (using hot water for soaking 2 days).
- From End Table to Aging Vessel: Reconditioning an old barrel. Ale of the Riverwards Blog by Ed Coffey. See also this this MTF thread on swelling an old, dry barrel.
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  , 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" .
Some producers remove heads from barrels during cleaning. This may be beneficial if whole fruit is used in the barrel 
MTF barrel cleaning threads:
- Alex Buck describes the barrel cleaning process for pyramid stacked barrels at Black Project.
- Advice on cleaning out an old wine barrel with dried mold in it.
- James Howat of Black Project Spontaneous Ales describes his process of rinsing and steaming a new 'Stella' foeder that is 11hL (~9.4bbl / 290gal). Steamed barrels should be allowed to cool before bunging; cooling with a bung installed can lead to imploding barrels. Steam just before filling is one way to avoid this problem .
- GW Kent barrel washer; video of washer in action by Ryan Fields.
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 other presumably better designed 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 . 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 found 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; 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 . 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. The French barrels required 12 minutes and the American oak barrels required only 9 minutes at 131°F (55°C). They could not culture Brettanomyces from the oak even after incubation of stave cross-sections in WRM for 60 days. 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 .
Swaffield and Scott (1995) found the yeast and 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 yeast and 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 .
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 . 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 .
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 . 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.
- Quality Assurance wikipage.
- MTF thread on ozone vs steam/boiling water for sanitizing barrels and breweries with a very detailed comparison of the two approaches from Nate Ferguson of Escarpment Labs.
- MTF thread discussion scientific studies about steam pasteurizing oak barrels.
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 .
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 . 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.
Sulfur Storage Solution Method:
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 (~40 min in)) is often used.
Update: The lined out instructions above have sometimes been advised by winemakers, and presumably taken from their instructions . 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) , and to check the barrel once a month and change the storage solution once a month if needed . The amount of citric acid is the same: 0.5 lb per 59 gallon barrel (1 gram per liter/0.13 ounces per gallon) . 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).
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 . 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 .
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:  [need to expand]
Used for sanitation. A separate cleaning procedure is needed separately from using ozone to sanitize.
- Barrel Builders video on barrel storage.
- Colton Schwartz overview of building an ozone machine.
- MTF thread on ozone vs steam/boiling water for sanitizing barrels and breweries with a very detailed comparison of the two approaches from Nate Ferguson of Escarpment Labs.
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
- Rocky Mountain Barrel Company repair videos.
- Brandon Jones recommends wet liner epoxy to seal cracks in barrels; use on the inside as per the manufacturer's instructions .
- Raf Soef demonstrates a broken barrel ring, with advice from MTF members on how to repair and why rings can break on MTF.
- Jeff McGuire's SOP for making a chalk and garlic paste for sealing light croze leaks (read the comments for concerns about this method).
- See also External Barrel Repair Articles.
- Comprehensive list of cooperage tools.
- 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 .
- 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") . 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 , however heavy build up of wine crystals can pose a problem . 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).
Left over wine crystals on the inside of the bunghole of a sour beer barrel. Image provided by Pedro Sarsama.
"Scaly" wine crystals from rinsing a barrel. Image provided by Stefan Wiswedel.
- 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).
- Advise from Andrew Zinn and others on barrel room layouts.
- MTF discussion on drains for barrel rooms.
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
- Barrel Builders 'Be Your Own Cooper' Lecture at the CCBA Fall Conference 11/14/16.
- Matt Albrecht at Southern Brewers Conference 2017 on Brewery Coopering Part 1 and Part 2
- A few practical beginner tips from Brandon Jones ("Working With and Repairing Old Wood for Barrel Aged beers", Craft Beer & Brewing Magazine).
- Practical Machinist spreadsheet of stave dimensions.
- Detailed cooperage instructions of a bucket (includes some techniques that are applicable to barrels, cooperage tools, and history):
Maintenance and Repairs
- Barrel Maintenance and Repair Manual, by Barrel Builders, Inc.
- Master Cooper Douglas Rennie at Seguin Moreau Napa Cooperage - Repairing Barrel Leaks Video
- Barrel Head Removal for Fermentation with Phil Burton
- American Lambic Blog - Barrel Maintenance for Lambic Brewing
- Citric Acid & Sulfite Barrel Preparation; M&M Wine Grape Company.
- Keeping It Clean - Barrel maintenance for those new to oak barrels; BYO article.
- Barrel Maintenance and Storage, Farmhouse Beer Blog.
- From End Table to Aging Vessel: Reconditioning an old barrel. Ale of the Riverwards Blog by Ed Coffey.
- Ryan Steagal's video of repairing a hole in the side of a barrel.
- The Sour Hour with James Shamas discussing small barrels for homebrewers
- Vadai Barrels Prep Instructions - good for small barrels.
- Barrel Builders video on how to tighten a barrel head using flagging.
- Barrel Builders video on using sulfur sticks.
- Barrel Builders video on repairing bore bug holes with spiles.
- Barrel Builders video on repairing a barrel that leaks between the head and stave/chime (croze).
- Using food grade epoxy to seal barrel leaks, by Jace Marti on MTF.
- Rack-It-Teer (recommended by Jay Goodwin on the Sour Hour ) 
- Bulldog Mfg
- GW Kent Bulldog
- The Eccentric Beekeeper Homemade Bulldog with Parts List
- My Pressure Racking Cane, A Beer Diary blog.
- MoreWine Gas Transfer Tool
- Brew Hardware Pressure Transfer Tool (Bulldog).
- HERIC Distribution (France; specify which fittings are needed) .
- M-Tec's Barrique-Absaugrohr (Denmark).
- Brandon Jones advises securing a stainless steel scrubby to the end of a racking cane using a stainless worm clamp for racking beer out of a barrel that contains hops/fruit in it .
Steamers and Cleaners
- Swash LG-SW-20 Steam Sanitizer.
- GW Kent Moog Barrel Cleaning System.
- GW Kent Barrel Washing Stand.
- GW Kent Electric Steam Cleaning Machine (20kW). 
- MOOG Cleaning Systems Barrel CIP.
- DIY $40 Barrel Washer by Brandon Jones.
- Gamavac and Evacublast from Gamajet (can remove fruit and lees from barrels ).
- Earlex Steam Generator. 
- DIY barrel steamer from Ethan Tripp.
- McCulloch MC1385 Deluxe Canister Steam System (cleans 2 barrels per fill; takes 10 minutes to get to boiling point) .
- DIY Barrel washing/inspection station by Jeff Porn (posted on MTF). and casters set recommended by Cameron Pryor . See also simple barrel cleaning station with two hand trucks by Kian Oveissi.
- Wagner 0282018, 705 Steamer 1-Gallon Wallpaper Steamer (modified with a triclamp connection), recommended by James Howat.
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. 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.
- Funk Factory Geuzeria - Pyramid Stacking Technique for Barrels
- MTF discussion of equipment for transferring out of pyramid stacked barrels and tap fittings.
- MTF discussion on securing bottom stacks when emptying.
- MTF discussion on stabilizing the barrels as they are stacked.
- Funk Factory Geuzeria - Barrel Tap.
- Glacier versus GW Kent barrel tap discussion.
- GW Kent Oak cask Fitting Adapter. Also see this tip from Jeff Porn on fittings.
- MTF tips and comparisons of benefits/disadvantages of barrel stacking versus using pallets/forklifts.
- TCW barrel racking wand that fits in-between pyramid stacked barrels. 
- Bokke (formerly Bokkereyder) reported that a stability engineer quoted that 7 levels of barrels in a pyramid stack using Bokke's structure was safe.
- MTF thread on racking beer out of barrels that are pyramid stacked where a bulldog can't fit, and options for solving this problem. Also discussions on what pumps to use.
- Mike Karnowski shows his hack for making a sealed bung connected to a CO2 purging line for pushing beer through a barrel tap with CO2.
- Alex Buck describes the barrel cleaning process for pyramid stacked barrels at Black Project.
- MTF Threads with demonstrations & discussions on using barrel taps:
- The "Jeff Porn" barrel taps in action. See also the tapping process.
- Using barrel taps with pyramid stacking.
- James Howat warns of minor leaking issues with Belgian corks; suggests trying tappered corks instead (work in progress).
- Mitch Ermatinger demonstrates his barrel tap and pump set up:
Porn Tap Parts List
- Barrel Tap
- 1/2" NPT threaded tri-clamp fitting
- Valve of some sort (this is what Jeff uses)
- 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) .
- Alasco Rubber & Plastics Corp. See also MTF thread about Alasco vs GW Kent ventilated bungs.
- Vin Table LLC.
- Ferm-Rite Ventilated Bungs for smaller barrels.
- GW Kent Barrel Fermentation Plus Bungs (wine barrel size). See also MTF thread about Alasco vs GW Kent ventilated bungs.
- AR Black & Co (Australia).
- Kauri Winemaking Innovation (New Zealand).
- Solid Dual Fermentation Bung (The Vintner's Vault).
- Duel Fermentation Bung (The Vintner's Vault).
- Ferm-Rite Silicone Bungs (Barrel Builders).
- Alasco Bung (GW Kent).
- Silicone Bung for small barrels (MoreBeer).
- Keystone Homebrew Supply (full-size barrel ventilated bungs and cooperage equipment.
- Ferm-Rite (Boswell Company).
Waxing Small Barrels
- Paraffin waxing a barrel, Funk Factory blog article.
- Great Fermentations Blog - Waxing Smaller Barrels with paraffin wax.
Embrace The Funk Tips
- Barrel Cleaning and Storage
- Barrel Repairs and Maintenance
- Barrel Filling Procedure
- Barrel Head Removal
- 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 
- 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) 
- Wax around the nail if it keeps weeping.
- 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 .
- 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 .
- Keep 2" steel nails handy in case the hole in the barrel head starts to get too big.
- Some brewers prefer stainless steel screws to nails, which may be easier to install and remove using a drill.
- McMaster-Carr Type 316 Stainless Steel Nail; 4D Size, 1-1/2" Length, Approximately 200 Pieces/Pack and the 6D Size, 2" Length for a backup if the hole gets bigger (as per Vinnie). Similar nails are also available on Amazon.
- Burgundeon Babble Belt Forum post by B-Dub that shares an email from Vinnie regarding his nail technique.
- See this MTF post for tips on getting a better flow if the beer trickles out of the hole, and this MTF post on which tools people prefer for pulling nails.
- First time experience of Travis "ColoradoFlyFisherman" on youtube installing a Vinnie nail in a barrel.
- For smaller barrels of 15 gallons and smaller, position the nail near the bottom of the head just above the croze. This will increase the hydrostatic pressure and help push a stream of beer out of the hole .
- Western Square Industries Barrel Rack catalog.
- "Cave rack" for the first row of pyramid stacked barrels.
- DIY barrel stand with wheels by Colin Burton (ideal for homebrewers).
- Tom Antidoot Jacobs shares his wooden racking/shelving design (3 levels high).
- Many barrel makers/brokers also offer racks for sale; see Barrel Sales below.
General Barrel Aging Information
- "Barrels in the Brewery", by Brian Hall of Brouwerij-Chugach; includes SA:V ratio for different barrel sizes
- Understanding Maturation – Part 1: Know Your Casks
- "Anson on Thursday: Oak ageing holds key to wine sweetness", an article on analyzing oak on a molecular level for desired qualities.
- BasicBrewing radio interview with CJ Shamus; great information on using small barrels for a sour beer program.
- Pumps that work well for barrel racking for pros.
- Discussion on diaphragm pumps and flex impeller pumps.
- Video that gives an overview of types of pumps in general.
- Troubleshooting problems with barrels that rack slowly.
Milk The Funk Tips and Discussions
- Dave Janssen's discussion on MTF about a CO2 Pressure Racking Cane for Barrels, with tips from Eccentric Beekeeper
- Ed Coffey's Cheap CO2 Racking Cane discussion on MTF
- Raf Soef's modified racking cane
- Autoclaving Alasco bungs.
- Tips on controlling primary fermentation in a barrel, including tips from Pierre Tilquin.
- Discussions about keeping barrels in hot and dry regions without temperature/humidity control.
- Using pallet stackers or power stackers for lifting barrels.
- Flow Meter recommendations.
- MTF quick tips on using barrels.
Sourcing Barrels - Manufacturers and Suppliers
- Black Swan Barrels.
- East Coast Wood Barrels.
- Rocky Mountain Barrel Company.
- Quality Wine Barrels.
- Adirondack Barrel Cooperage - American White Oak, new whiskey barrels.
- The Oak Cooperage (American Oak for whiskey and wine).
- J. Dias Cooperage.
- Kelvin Cooperage.
- Country Connection (Legacy Cooperages).
- Keystone Fermentation Supply (also has foudres).
- Northeast Barrel Company (east coast and west coast locations).
- Midwest Barrel Company (wine and spirit barrels; offers smaller sizes).
- The Barrel Broker.
- Wineoakbarrels.com (Europe).
- Wilhelm Eder - commercial-sized barrels available in Europe.
- Used Wine Barrels on Winebusiness.com.
- Probrewer Classifieds.
- Woodenville Whiskey barrels.
- American Barrel Exchange (might be defunct).
- Riverdrive cooperage (Where Allagash sources barrels).
- If you live in a wine-producing region, meet your local winemakers and join local winery forums to see what sorts of used stuff comes up.
- Thorslunds Kagge (Sweden).
Offers Smaller Sizes
- Oak Barrels, Ltd.
- The Barrel Mill.
- American Barrel Exchange.
- Vadai Hungarian barrels.
- Barrels Unlimited (many sizes).
- The Oak Cooperage (American Oak for whiskey and wine; offers 30 gallon, may not ship ).
- Austin Homebrew Supply (American oak 5 gal barrel).
- Adirondack Barrel Cooperage - American White Oak, new whiskey barrels (offers pro and homebrew sizes).
- Midwest Barrel Company (wine and spirit barrels; offers pro and smaller sizes).
- Black Swan Cooperage, LLC; 5, 8, 10, 15, 23, 30, and 53 gallons (call them, see this MTF thread).
- W. Elder - Smaller sized barrels available in Europe.
- Used and new barrels in Sweden.
- 5, 10, and 15 gallon from Farmhouse Brewing Supply (might require joining an emailing list).
- Woodenville Whiskey Co barrels (small and large sizes).
- Wine Oak Barrels (UK). Reportedly waxes the insides of smaller barrels .
- Keystone Homebrew 15 gallon "Dad's Hat" Rye Whiskey Barrels. (Recommended by Ed Coffey.)
- Thorslunds Kagge (Sweden). See this MTF thread for example usage.
- BrewTek 20-40L foeders (Canada).
Used Homebrew Sized Used Barrels
- Woodinville Whiskey Co - 8 gallon barrels used for whiskey aging
- Balcone's 5 gallon spirit barrels - The homebrew supplier for Balcone's 5 gallon spirit barrels
- Woodinville Whiskey Co. 8 gallon used whiskey barrels.
- Great Lakes Bourbon Barrels.
- Adventures In Homebrewing - used 15 gallon whiskey barrel.
- Homebrewing.com - used 5 gallon whiskey barrel.
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.
OakWoodBarrels.comThis website is a scam; do not purchase barrels from them . See this MTF thread.
dirtcheapbarrels.comThis website is a scam; do not purchase barrels from them. See this MTF thread.
Additional Articles on MTF Wiki
- Conversation with Jason Sledd on Milk The Funk. 05/03/2015.
- MTF discussion about bourbon barrels
- Review of quality factors on wine ageing in oak barrels. Garde-Cerdan and Ancin-Azpilicueta (2006)
- Effect of oak barrel type on the volatile composition of wine: Storage time optimization. Garde-Cerdan and Ancin-Azpilicueta (2006)
- Quercus petraea. Wikipedia. Retrieved 06/16/2018.
- Brandon Jones. Private correspondence with Dan Pixley. 06/16/2018.
- 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
- Justin Amaral. Milk the Funk Facebook post on measuring oxygen in barrels. 02/15/2018.
- Julien Miguel. "Anatomy of a Wine Barrel: Parts, Sizes, Infographic". Social Vignerons website. 06/27/2016. Retrieved 07/31/2018.
- Joseph Kearns, Justin Amaral, and Andrew Zinn. MTF thread about tightening hoops on French oak barrels. 01/23/2018.
- Milk the Funk Facebook Oak discussion
- Milk the Funk Facebook member brew CC
- Milk the Funk Facebook Oak discussion
- Milk the Funk Facebook Oak discussion
- Milk the Funk Facebook Oak discussion
- Basic Brewing Radio barrel progression
- Funk Factory Barrel Waxing
- James Shamas. Milk The Funk Facebook group. 07/13/2017.
- Various MTF Members. MTF thread about how long to wait to fill a new spirit barrel. 11/16/2017.]
- Jester King on the Sour Hour part 2
- "5 Tips on Barrel Aging from Avery Brewing Co." Andy Parker on the AHA website. Retrieved 05/10/2016.
- Various MTF members. Milk The Funk Facebook thread about Aardwolf Brewing Company in Jacksonville started by Derek Springer. 07/07/2017.
- Brandon Jones. Milk The Funk Facebook group thread on hotter temperatures for barrel rooms. 04/15/2018.
- Matthew Fields. Milk The Funk Facebook group post on wine barrel triclamp taps & manways from Glacier tanks. 02/16/2018.
- Milk The Funk Facebook group thread on how to seal the bung in a barrel. 05/02/2019.
- The Sour Hour Episode 16
- Barrel Steam Wand
- Conversation about steaming barrels and bunging on MTF. 05/31/2017.
- Joshua Martinez and Levi Funk. Milk The Funk Facebook group thread on swelling large casks with cold water. 06/13/2018.
- "Chloramine". Wikipedia. Retrieved 09/14/2016.
- "Chlorine". Wikipedia. 09/14/2016.
- "Chlorine Use in the Winery". Christian Butzke. Purdue University. Retrieved 09/14/2016.
- Crooked Stave facebook post 2-Nov-2015
- Conversation about steaming barrels and bunging on MTF. 05/31/2017.
- 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.
- Heat inactivation of wine spoilage yeast Dekkera bruxellensis by hot water treatment. Fabrizio, Vigentini, Parisi, Picozzi, Compagno, Foschino. 2015.
- Brettanomyces bruxellensis yeasts: impact on wine and winemaking. Monica Agnolucci, Antonio Tirelli, Luca Cocolin, Annita Toffanin. 2017.
- 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.
- 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.
- Nate Ferguson of Escarpment Labs. Milk The Funk Facebook thread about using ozone to sanitize barrels. 10/24/2017.
- Wines & Vines website. "Barrel-Washing Protocols". Jan 2013. retrieved 10/24/2017.
- MTF poll and various MTF members on storing barrels empty vs full. Milk The Funk Facebook group. 11/17/2017.
- 2016. Laffort sulfur disc instruction manual. South Africa
- The Sour Hour with Tim Clifford of Sante Adairius
- M&M Wine Grape Co. Citric Acid & Sulfite Barrel Preparation. Retrieved 03/06/2016.
- Mike Makris. Milk The Funk Facebook group. 04/12/2017.
- The Sour Hour Episode 28 (~49 minutes in). Jay Goodwin from The Rare Barrel. 02/17/2016
- 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.
- Andrew Zinn. Milk The Funk Facebook group. 05/19/2017.
- Andrew Zinn on rinsing barrels with cold water first. Milk The Funk Facebook post. 11/18/2017.
- Ozone sanitation for barrels
- Brandon Jones. Milk The Funk Facebook group thread on repairing a crack in a foeder. 11/17/2018.
- Lambicland by Webb, Pollard and McGinn (2010)
- Conversation with Gareth Young and Raf Soef on MTF regarding lambic barrels. 09/22/2015.
- Wikipedia. Potassium bitartrate. Retrieved 09/30/2015.
- Monash Scientific. Potassium bitartrate. Retrieved 09/30/2015.
- Conversation in Milk The Funk about tartrates. 09/30/2015.
- UNDERSTANDING WINE TARTRATES. Jordan Winery. Retrieved 09/30/2015.
- Brandon Jones. Milk The Funk facebook comment on wine crystals. 10/10/2017.
- The Sour Hour Podcast, Episode 39, ~56 minutes in. Jay Goodwin. Retrieved 08/06/2016.
- Anthony Baraff. Milk The Funk Facebook thread on bulldogs in Europe. 04/17/2019.
- Brandon Jones. Milk The Funk Facebook group. 07/11/2017.
- Sean McVeigh on GW Kent steamer. Milk The Funk Facebook group. 11/1/2017.
- MTF conversation with Brandon Fender regarding cleaning barrels. 08/31/2016.
- Steamer recommendation from Gregory Wilhelm on MTF. 09/06/2016.
- Conversation with Cameron Pryor on steam cleaners on MTF. 11/20/2016.
- Conversation 1 with Cameron Pryor on MTF about a barrel steaming station. 11/20/2016.
- Conversation 2 with Cameron Pryor on MTF about a barrel steaming station. 11/20/2016.
- Tristan Stewart. MIlk The Funk Facebook thread on Tristan's brewery and racking wand for pyramid stacked barrels. 02/07/2018.
- Question on MTF regarding what type of bung/airlock. 12/24/2016.
- Quoted email from Vinnie Cilurzo on the Burgundian Babble Belt forum. Retrieved 12/1/2016.
- Andrew Zinn on MTF. Drilling a Vinnie Nail. 08/29/2017.
- Mattias Terpstra on MTF. Vinnie Nail diameter for metric. 08/29/2017.
- Various MTF members. Tools for removing a Vinnie Nail. 08/29/2017.
- Sean McVeigh on MTF. Removing a Vinnie Nail without making a mess. 08/29/2017.
- Matt Warren. Milk The Funk Facebook group post. 10/05/2016.
- Private correspondence with The Oak Cooperage by Caleb Buck. 02/13/2017.
- Conversation with Ryan Sealey on MTF regarding Wine Oak Barrels . 01/29/2017.
- "SCAM ALERT: Fake bourbon barrel company deceives customers". Chris Chandler. WLKY newspaper website. 12/21/2018.