Brew-in-a-bag (BIAB) is a simplified all-grain brewing technique that developed about a decade ago among Australian homebrewers. Whether you’re new to brewing, an extract brewer looking to jump to all-grain batches, or an experienced all grainer who wants to speed up the brew day, BIAB offers an attractive alternative to traditional methods.
As the name suggests, brewing in a bag involves brewing in…well…a bag. In traditional brewing rigs, grain is mashed in a mash-lauter tun, after which time wort is drained into the boil kettle. Either in batches or as a continuous process, the grain is rinsed with sparge water from a hot liquor tank to wash additional sugars from the grain bed.
Brewing in a bag obviates the need for such a complex setup by using the boil kettle itself for the mash. The brewer lines the kettle with a large, sturdy mesh bag to contain the grain, and the grain is mashed using the full volume of water needed for the batch, plus a bit extra to account for absorption. When the mash is complete, the bag is lifted out of the kettle and allowed to drain completely. The wort is then boiled, hopped, and chilled as in traditional systems.
Brewing in a bag offers some tremendous benefits to both novice and experienced all grain brewers.
- Modest equipment needs. Unlike traditional three-vessel systems, which feature separate mash-lauter tuns, hot liquor tanks, and boil kettles, BIAB requires just one large kettle for the whole process from mash-in to knockout. The only special piece of equipment is the mesh bag itself, which can be made at home or purchased from a homebrew retailer.
- Speed. Traditional batch or fly sparging can take anywhere from fifteen minutes to an hour or more, depending on your setup. Brewing in a bag eliminates the sparge altogether, and you can fire up the boil kettle as soon as the mash is over (just make sure to lift the bag first!).
- No stuck sparges. The stuck sparge is that dreaded phenomenon in which runoff stops before the full volume of wort has been collected, and it’s usually caused by too fine a crush, gummy grains such as wheat and rye, or a lautering device that easily clogs. With BIAB, there’s no risk of a stuck sparge because there’s no sparge to begin with.
Nothing comes for free in life, and virtually every gain in simplicity carries some kind of penalty. With BIAB, the disadvantages can almost always be reduced or eliminated with a change in process or a bit of extra equipment.
- Potentially reduced extract efficiency. Extract efficiency refers to the amount of sugar extracted from grain relative to the potential sugar available in that grain. Grains are typically sparged to wash sugars into the boil kettle, but BIAB is a no-sparge method, which means some sugars may remain behind. That said, brewers who have experimented with the method have found that the fine mesh of the nylon bag permits a much finer crush than would be suitable for other lautering methods. The efficiency gains of the fine crush can offset efficiency losses associated with skipping the sparge.
- Kettle requirements. Because you mash directly in the brew kettle, you need a brew kettle capable of holding the entire pre-boil volume, PLUS the volume of the grain itself, PLUS the water absorbed by the grain. This means that brewing a 5-gallon batch, which typically has a pre-boil volume of 6 or 7 gallons, may necessitate a kettle of 15 gallons or more.
- Heavy lifting. When the mash is complete, you have to lift the grain out of the kettle using the bag in which it was mashed. This means you need a strong bag and a strong upper body. Some BIAB enthusiasts construct special pulleys to lift the bag of wet grain out of the kettle. Such pulleys offer the ability to suspend the bag over the kettle so that wort can drip down into it as the burner is fired up.
If you’ve been putting off all-grain brewing because of equipment concerns, BIAB is an excellent way to try out the process and get a feel for working with grain without investing in a ton of new equipment.