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Brew in a Bag (BIAB)

Brew in a Bag

Brew in a Bag or BIAB is a simple brewing technique in which a brewer can step into all-grain or partial mash brewing for very little expense and with minimal equipment. This technique also has the added benefit of having less equipment to set up and clean.

The general idea behind BIAB is that instead of using multiple kettles such as a Hot Liquor Tank, Mash Tun, and Boil Kettle, the brewer only uses one large kettle with a bag inside that holds all of the grains.


 The only required equipment for BIAB brewing is a large kettle, ideally 10 to 15 g for 5-gallon batches; a nylon bag that is large enough to line the inside; and a burner to heat the kettle. If you are going to be directly heating the kettle while the bag is in place, it is also a good idea to have a false bottom or colander screen installed to keep the bag from burning. Another item that is extremely useful is a pully system which will save your back from injury when trying to lift out the water-soaked grains.

The Brewing Process:

 You will begin brewing by filling the kettle with your strike water. For a 5-gallon batch, the pre-boil target will be approximately 6.5 gallons, so keeping in mind that there will be some water absorption from the grains (approximately 1-pint per lb. of grain), there is a simple equation that we can use to help calculate the correct amount of strike water.

Strike water volume in gallons: (Total grain weight in lbs.) x 0.125 + 6.5

Preheat your water to the desired temperature. A good general guideline is to heat the pre-heat the water approximately 10°F higher than your target mash temperature and then place the bag and grain into the kettle. You will then thoroughly stir the grain to make sure that there are no clumps.  Once the grains have been added and mixed, put the lid on the kettle to hold the temperature. You will want to mash the grains for approximately 45-60 minutes to ensure that all of the starches convert to sugars.

After the mash has been completed, you will then do a mash-out by heating the kettle to 168°. This will help to improve your overall efficiency. You can then lift out the grain bag and hold it above the kettle for it to drain. Some brewers create hooks and pulley systems to help with this stage.

After the grain is finished draining, you can then discard the grains and begin your boil, completing your brew process as normal.

Many people feel that the overall efficiency that you get from BIAB is not quite as high as standard mashing and is more in line with that of “No Sparge” brewing. Although there are many brewers who are getting outstanding efficiency from BIAB. If you do end up with a lower-than-expected efficiency, many brewers find that milling their grains through the mill more than once usually helps them in extracting additional sugars. You can also make adjustments to your grain bill by adding additional base grains to compensate.


If you have any questions regarding the Brew In A Bag process, the staff of The Brew Hut are always here to help.



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