What is BIAB (Brewing-in-a-Bag)?


By Columbus P. Fuggles
BIAB (Brewing-in-a-Bag)
Beginning a new hobby can be an exciting experience but it can also sometimes be a daunting one. Consider the jargon involved in joining the homebrewing community: one could be forgiven for quickly becoming confused reading the language involved in homebrewing techniques. Many terms used by authors and brewers come from Latin, German, Greek, or Old English – not common in Modern English parlance. Some terms are acronyms that writers throw in assuming readers know them. And some terms don’t even register as words. Take BIAB, for example. What is BIAB, how can it help you, and how can learning this one acronym save you time, space, money, and most importantly headache?
BIAB stands for “Brewing-in-a-Bag”. Often relegated to a subsection or footnote of many texts and sometimes omitted altogether, even in major texts like John Palmer’s How to Brew or Randy Mosher’s Mastering Homebrewing, BIAB takes up just one or two paragraphs. Palmer writes, “The brew-in-a-bag (BIAB) method turns the traditional process on its head by removing the grain from the mash instead of removing the wort (Old English, literally “spice”) from the grain”1. Mosher describes BIAB as “replacing a stainless mash basket with a cloth one…. A mash is made as usual, and after mash-out, the bag is lifted by its handle so it’s free of the wort, allowed to drain for a time, maybe squeezed and prodded a bit, then the mash is discarded”2. In essence, BIAB is a simplification of the sparge (Latin, literally “to sprinkle”) process.
So how can BIAB save time? Traditionally, once mash is complete, brewers typically vorlauf (German, literally “recirculate”) their wort. They recirculate the wort over a false bottom of the tun (Old English, “barrel”) so that particles are not suspended and contribute off-flavors during the boil. BIAB eliminates the need for this step completely! Because there is no false bottom, only a cloth bag, the next step in the process is to lift the bag from the pot! As Mosher says, some folks squeeze the saturated grain to get some of that last bit of fermentable sugar out.
Eliminating the lauter (German, literally “clear”) tun completely can save the homebrewer hundreds of dollars! Cloth – or now space-age fabrics like nylon – bags are not only reusable, cheap, and sustainable, they also come in a variety of shapes and sizes to fit your brew pot. Instead of another piece of brewing equipment taking up space in the garage between brew days, you can rinse your bag, throw it in the washing machine and fold it with the rest of the laundry.

Basic Overview of BIAB (Brewing-in-a-Bag) process: 

  1. Decide on a recipe
  2. Because there will be no sparge, heat a final volume of water to strike temperature. Some brewing software has built-in BIAB calculators to easily compute the final volume.
  3. Submerge your grain bag into the hot water and either dunk the grain or use a paddle or whisk to break up “dough balls” that may stick together once the bag is submerged. Ensure that each grain is surrounded by water.
  4. If using a step-mash schedule, make sure your grain bag is not resting on the bottom of the heating vessel. Some brewers stretch the edge of the bag over the edge of the vessel or use clothespins or clips to keep it in place and prevent it from scorching along the bottom.
  5. When the mash schedule is complete, raise the bag from the water. Some brewers use a colander or drying rack resting over the vessel so the bag can drain. Others use a bucket (or set of buckets) to press the grain bag to extract any last fermentable sugars.
  6. Boil as regular! Spent grain makes great stew, bread, or dog treats!


1 Palmer, John. How to brew: ingredients, methods, recipes, and equipment for brewing beer at home, Boulder, Colo. : Brewers Publications, [2006], p. 300.

2 Mosher, Randy. Mastering Homebrew: The Complete Guide to Brewing Delicious Beer, Chronicle Books, [2015], p. 124.


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