A foeder (pronounced FOOD-er) is the Dutch word (originally "voeder" in Dutch, and perhaps changed by Rodenbach's French-speaking management to adopt the "f" from the French version, "foudre" ) for a large wooden vat used for either long term fermentation or primary fermentation. In Dutch, the synonym "vaten" is often used, which translates to English as "vat". The term "vat" is used in the United Kingdom. In Germany, the term is "fass" (translates to "barrel" in English) or sometimes "Großefass" (translates to "big barrel" in English), which is phonetically related to "vat" in English or "vaten" in Dutch (note that "holzbottich" is the German word for open-top wooden vessels) . It is written as "foudre" in French, or "foedre" by some American breweries (the word "foudre" in French more typically means "thunderbolt" ). A foeder can range in size from 600 to 1 million liters .
- "As for the Foeders, you'll want to get the Foeder in place and swollen right away. Hot Liquor from your HLT will do the job. I really like to set up a CIP type loop. About 1 bbl of HLT liquor in the foeder then a loop with a spray ball up top in the foeder through the manway hole. Then we use a product called ACTO 140 sold by Birko chems [Birko Chemicals]. *Editor update: dosage is 1-2 ounces per gallon of 140F water; typical exposure time is 15-30 minutes, and then rinse . See also sodium percarbonate.* We loop that for about 30-60min. Then rinse with HLT liquor. Then if you can't purge with CO2 and fill with beer the next day we fill the Foeders up with potassium metabisulphite and citric acid. The rate is 2g of Kmeta and 1g of citric acid per litre of filtered water. Then keep this in the Foeder till you are ready to empty and fill with beer." - Chad Yakobson in an email to Brad Primozic; independently verified and approved for publication by Chad Yakobson in a private email with Dan Pixley .
- Rocky Mountain Barrel Company advises that when hydrating a new dry foeder, it is best to fill it incrementally. Otherwise, the pressure from being completely full will be too strong for any leaks towards the bottom of the tank to seal .
- As with barrels, thoroughly rinse the citric acid and potassium metabisulphite from foeders before filling them. Flush them with CO2 as well before using them if possible .
- James Howat of Black Project Spontaneous Ales describes his process of rinsing and steaming a new 'Stella' foeder that is 11hL (~9.4bbl / 290gal), and made of Slovenian Oak.
- Tips and advice on reviving a 100 year old foeder.
- Swelling a foeder in one day with garden mister heads, by Mat Waddel and Jace Marti.
- MTF thread on ozone versus steam for foeders.
- Brandon Jones recommends wet liner epoxy to seal cracks in barrels; use on the inside as per the manufacturer's instructions .
Egg shaped foeders sit horizontally and are reminiscent of an egg shape. This has the benefit of taking advantage of vertical space, as well as limiting headspace more so than traditional foeders .
The following businesses specialize in the crafting and/or selling of foeders.
- Foeder Crafters
- Premier Wine Cask.
- Rocky Mountain Barrel Company (May not be reflected on website; offers barrels converted to foeders)
- Wilhelm Eder 
- Keystone Fermentation Supply.
- Foeder Smith (also has very small foeders for homebrewers).
- Quercus Cooperage (also has homebrew scale foeders.
- French Perle de Quintessence Pression (technically not a foeder). See also this MTF thread for reviews/discussion of this product.
- Discussion on upright versus horizontal foeders.
- Thread with tips on building foeders.
- Thread about a Ron Pattinson book passage ("Strong!") on brewers putting sand on the lids of their wooden vats.
Additional Articles on MTF Wiki
- Roel Mulder. "A small history of Flemish old brown (and red) – 1." 08/11/2020.
- Kunze, Wolfgang. "Technology: Brewing and Malting, Sixth Edition." 2019. Pgs 31,32.
- Großes Fass des Heidelberger Schlosses. German Wikipedia. Retrieved 01/21/2020.
- Benedicht Koch. Private correspondence with Dan Pixley on the German word for "foeder". 01/18/2020.
- Foudre. French Wikipedia. Retrieved 10/23/2019.
- Dutch Wikipedia. Rodenbach (brouwerij). Retrieved 10/23/2019.
- Martyn Cornell. Zythophile magazine. 10/18/2019. Retrieved 10/23/2019.
- Ron Pattenson. Shut Up About Barclay Perkins blog. 05/10/2019. Retrieved 10/23/2019.
- Jim Dykstra. "What is a Foeder?". The Beer Connoisseur. 09/08/2016. Retrieved 10/23/2019.
- Reported communication with Dana Johnson by Nicki Sener. Milk The Funk Facebook group. 09/09/2023.
- Conversation with Brad Primozic on the Milk The Funk Facebook group. 3/5/2015.
- Rocky Mountain barrel Company Facebook post. 10/30/2019.
- Conversation with Mike Makris of The Rare Barrel and Brandon Jones of Yazoo Brewing Co regarding rinsing and flushing foeders. 12/22/2015.
- Brandon Jones. Milk The Funk Facebook group thread on repairing a crack in a foeder. 11/17/2018.
- Shane Stewart and Ryan Buxton. Milk the Funk Facebook group post on egg shaped foeders. 02/16/2018.
- Conversation with Jeff Porn on MTF. 5/25/2015.