How to Brew In A Bag (BIAB)

Making the move to Brew in a Bag (BIAB) is a great way to get into all-grain brewing. Not only is everything done in one kettle, the process is much less complicated than a normal all-grain brewing. Plus, it can be done in even the smallest of spaces. Simply put, this is how Brew in a Bag works:

Your grains go into a bag. The bag goes into a brew kettle containing pre-heated water. After an hour, the bag is removed from the brew kettle. The brew kettle now contains ready-to-boil wort. Simple, right? BIAB also removes the need for sparging  (the process where hot water is run through the grains after mashing to extract as much fermentable sugar as possible). Removing this stage cuts the length of an average brew day by at least an hour. And as everything’s done in the one kettle, there’s not too much cleaning to be done afterwards.

Personally, I made the switch from full-mash all-grain brewing to BIAB as it gave me the freedom to quickly brew small batches of around 1 gallon (4.5 liters). Not only did this let me experiment with different recipes, but I could also brew on my kitchen stove. And if something went wrong, I wasn’t lumbered with 5 gallons (23 liters) of undrinkable beer.

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Equipment needed to Brew in a Bag

biab false bottomBrew kettle – You’ll be using your brew kettle to both mash and boil. Make sure to use a brew kettle that can hold the entire pre-boil volume of water in one go, and won’t overflow once the grains are added. For example, a 5-gallon brew will need a kettle that can comfortably hold 7-8 gallons (31-36 liters) of water.

Bag – In the past, homebrewers used to make their own bags from materials like voile – a fine, mesh-like fabric used for soft-furnishings, such as curtains. Nowadays many homebrew suppliers stock BIAB bags. Commercial bags usually come with straps which can be used to easily pull the bag out of the kettle once the mash is complete. Again, this helps to make brew day as simple as possible. Tip: Place an upside down metal sieve at the bottom of the kettle. This acts as a false bottom, allowing the water to circulate throughout the bag.

Brew in a Bag step-by-stepbiab mash

Step 1 – Heat the water and add the entire pre-boil volume of water to the kettle and heat to the target strike temperature. This is usually around 160 for a five gallon batch, as the grain addition will cause the temperature to drop.

Step 2 – Add the grains Once the strike temperature is hit, turn off the heat and put the bag into the kettle, ensuring a good overhang around the kettle to stop it from slipping in. Next, add the grains. Make sure they are fully submerged and stir gently until there are no more pesky dough balls in the mash. Once the grains are added, and the dough balls removed. put the lid on your kettle to reduce heat loss.

Step 3: Mashing – By mashing in a kettle, heat will be lost at a faster rate than if using an insulated mash tun. Keep an eye on the temperature. If it starts to drop, add more heat from whichever heat source you are using (e.g. gas). Another approach is to wrap a blanket round the kettle. Obviously, remove the kettle from the heat source before reaching for the blanket! No matter what option you go with, don’t reduce the mash time. Since there is no sparge stage, this is the only opportunity you have to extract as much of the fermentable sugars as possible.

BIAB mashout

Step 4: Collecting Wort – After about 60-70 minutes, the mash stage should be complete. Slowly pull the bag out of the pot and let any excess water drain into the wort below. Be careful, the bag will be very hot. To get as much wort as possible out of the grain, I keep a separate bucket handy with a colander placed in the bottom. After mashing, put the grain bag in the colander and leave alone for about 10 minutes. This should result in some additional wort being collected at the bottom which can then be added back to the brew kettle. Some others will set up a pulley system with a ladder to hang the grain bag over the kettle so the wort will drain right into the kettle.

That’s it! The wort should now be ready for the boil. From here on out the steps are the same as if you were doing an extract or all-grain brew.

A Note on efficiency

A known downside of the brew in a bag method is that sometimes brew house efficiency can dip, but there are ways around this. Ways to increase BIAB efficiency include:

Actually Sparge – While BIAB is designed to be as simple as possible, you can still sparge after the mash. In a separate kettle heat some water to 170F (76C). Take your grain bag and submerge it in this water. Give it 10 minutes, then add this liquid to the rest of the wort.

Mill the grains as finely as possible – You can't do this with a regular all grain batch due to the risk of a stuck sparge. Since there is no dedicated sparge, you can mill the grain very finely without any risk.

Mash out for 10 minutes at 170F (76C)Shop All Grain kits

Brew in a Bag and high-gravity beers

When brewing in a bag, the grain bill is limited by the bag’s size. This can be a problem when brewing grain-hungry high-gravity recipes, as there’s a danger that the overfilled bag could split when you pull it out of the wort. There’s a couple of ways around this: one is to simply brew smaller batches of beer.

 

Alternatively, ensure you use a sturdy, properly stitched bag that is capable of securely holding a lot of grain. Remember, that sucker will be heavy when it comes time to drain it. There’s a whole bunch of forums out there covering both efficiency and high-gravity beers using brew in a bag. If your new to this type of brewing, I’d give it a go first before trying to compensate for any lack of efficiency or gravity.

Hopefully this beginner’s guide gives you everything you need to get started with brew in a bag. While this method is all about simplicity, it’s also an excellent introduction to all grain.

Happy brewing!


Tim Witherow is a writer and homebrewer based in Kent, England. Follow him on Twitter @withert.

written by Timothy Witherow

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