Technique: Brew-In-A-Bag

Learn how to brew great beer with one of the easiest all-grain methods available.

Hi homebrewers,

Making the move to a traditional all-grain set-up can be daunting, especially the idea of having to purchase a mash-tun, a huge kettle another pot, for sparge water and lots of other expensive equipment. But fear not, there is a way to brew all-grain without having to buy lots of expensive equipment: a technique called Brew-In-A-Bag or BIAB.

What is BIAB?

Traditional all-grain brewing requires using a large mash tun (often a 50 L esky/cooler) in which the milled malted barley goes with hot water, before being drained and rinsed (sparged) a number of times to extract the wort. It requires calculations of temperatures and volumes for the water used in the initial mash and then again for sparging. This means that you need a mash tun fitted with mesh pipes to ensure drainage, a kettle to collect and boil your wort and another large pot to bring your sparge water up to temperature. While this is a process that’s been followed for many hundreds of years, there is an easier way, without all of the expensive equipment.

BIAB originated in Australia about 10 years ago. Basically, BIAB is a single-kettle, full-volume (usually about 35 L) mash done inside a large fine mesh bag (often a fabric known as voile). After mashing, the mesh bag containing the grain is removed and allowed to drain. The resulting wort is then treated as normal and boiled with hops added at various stages for bittering, flavour and aroma.

What are the pros and cons of BIAB over traditional all-grain methods?

There are many benefits to choosing to go down the BIAB route. These include:

  • Ease. BIAB is perhaps the easiest of all all-grain methods. Very little equipment is required. At very least, you will need 40-50 L kettle, a propane burner and a large voile brew bag (you should be able to get these from your local HBS or eBay).
  • Quality. BIAB can make beers as good as any traditional all-grain method. I brew BIAB and produce great beer that everybody loves.
  • Cheap. Compared to other methods of all-grain brewing, BIAB is relatively cheap, requiring very few pieces of new equipment.
  • Flexibility. BIAB is a very forgiving method and its ease means that even new brewers will be making fantastic beers without too much effort or practice.
  • Space-saving. With very little equipment, BIAB takes up a small amount of space. Perfect to those living in small apartments or town houses.

There are however, while very few, limitations and disadvantages to BIAB

  • Heavy. A water-logged bag of grain can be heavy and requires a bit of strength to lift it. Many people will go down the route of setting up pulley systems to deal with this.
  • High-gravity beers. While not impossible, fitting a large grain bill (over 6 kg) into your kettle might be a bit challenging if you’re attempting to do a full volume brew. There are work-arounds, but 10 kg of wet grain is going to be heavy!
  • Dangerous. Okay, I’ll admit, lifting a big bag of really hot grain out of a big pot full of hot liquid can be a tad stressful. Really though, provided that you use care you should be okay. A pulley system, even if it’s just a rope slung over the clothesline (like me) will help.

As you can see, it’s pretty clear that the benefits outweigh the negatives greatly. So let’s have a look at how to brew-in-a-bag.

How to BIAB.

The method for BIAB is pretty simple, but we’ll run through it step by step.

Step One: Strike water

Depending on how long you’re planning to boil your wort, you’ll need to adjust your initial water volume. Many recipes will recommend that you boil your wort for 90 minutes. This is a great way to minimise the DMS (the cooked corn flavours) and it’s pretty much what I stick to. Also, the grain will absorb a fair bit of water – usually about 0.6 L / kg (0.3 quarts / lb). For me, this means that I usually use about 35 L (9.25 gallons).

Next we need to heat the water. If your recipe says to mash at 66ºC (151ºF), then you’ll need to make your water a bit hotter. This is to account for the temperature drop that will happen when you dump in your colder 5 kg of grain. When it comes to strike water temperature for BIAB, there’s two ways to do this: fast and loose, or measured and accurate.


  • Fast and Loose. A pretty easy way to hit your strike temperature is to aim for 2ºC (3.6ºF) hotter than your mash temperature. Depending on how much grain you have, you may over- or under-shoot your temperature. If this happens, add some boiling water or stir like crazy until you hit your temperature.
  • Measured and Accurate. The second way doesn’t take much more effort, just a few calculations. Luckily, I’m a lazy bastard and there are a couple of great pieces of software, like Beersmith and Brewer’s Friend, that can help you with these. It’s pretty simple, just punch in information like the weight of your grain, the grain temperature, the grain to water ratio and your target temperature, and it will tell you what strike temperature you’re going for.

Right, so now you measured out your water and it’s up to temperature. Let’s move onto the next step.

Step Two: Cracking the grain

Milling your grain is essential to proper conversion. The milling process cracks the grain open so the hot water can mix the enzymes and starch and convert it into that sweet sweet wort. Anyway, you want the grain to be milled so at least some of the husks are left intact. If the grain is cracked too fine it will drain poorly. Too large and it won’t convert properly. If you’re a lazy bastard like me then just get your home-brew shop to mill it for you.

If you’ve got specialty grains like oats, rice or corn, then you might benefit from adding some rice hulls. These will help your mash drain properly when it comes time. Just chuck a few big handfuls in and mix it around.


Step Three: Doughing-in

Next step is doughing-in. Basically, doughing-in is a fancy term for mixing the cracked grain with the water. Line your kettle with your brew bag, take the temperature to ensure the strike water is correct and begin slowly pouring in your grain into the water. Stir the grain in while you pour, ensuring that no clumps of grain form. If they do, just break them up. Once you’ve mixed in all your grain check the temperature again. If you’re off your mash temperature, then now’s the time to add more heat or keep stirring until the temperature comes down. Probably don’t do this in socks like I was.


Step Four: Mashing

Right, so we’ve cracked our grain and doughed-in. Now what. Well, not much. Wrap the kettle up in a couple of blankets and let it sit for 90 minutes for the enzymes to do their thing. I use one of those thin foam camping mats, then wrap a big old second-hand blanket around it.


What happens during the mashing process?
Basically, malted grain is grain that has sprouted, before being kilned to stop the germination process. The sprouting process increases the amount of enzymes in the grain. For the plant, these enzymes convert the starches in the grain, supplying it with everything it needs to start growing into a new plant. For brewers, we use these enzymes to convert that starch into sugars – both fermentable and non-fermentable. Mashing at different temperatures will create different proportions of fermentable to non-fermentable sugars. More fermentable sugars will create a beer with a very light body and a higher ABV, whereas more non-fermentable sugar will create a beer with big body, but less alcohol. More grain will make a more alcoholic beer. Once we have released these sugars, we boil the liquid with hops and ferment it – creating beer.
Step 5: Drain the bag

After our 90 minutes is up, it’s time to drain the bag. You can just pull it out (carefully) and hold it like a sucker, or figure it out and tie it up to drain for 10-15 minutes. I tie it to my clothes-line. After this, if you want a bit of extra wort you can give the bag a light squeeze. Don’t squeeze it too much though, otherwise you’ll start to extract tannins from the grain and make the beer taste harsh.


Step 6: Bring the wort to a boil

So the next step is pretty easy too. Just follow your recipe. Bring the wort to a hot break. This is where it’ll foam up initially, then fall back down into the wort. Start your boil timer from this point. Your recipe will most likely tell you to boil between 60 and 90 minute. You’ll most likely add bittering hops in at around 60 minutes, then depending on your style perhaps more at 20 minutes for flavour and in the last 5 minutes for aroma. When you’re adding hops you can use little tie-up cloth bags or you can use a hop bazooka like the one in the picture.


Step 7: Cool the wort

There are lots of ways to cool your wort. Traditionalists will advise you to cool the wort as quickly as possible. This requires immersion or counter-flow chillers and a whole lot of water. These devices are also expensive. Okay to be honest, the quicker you chill the more pronounced your aroma hops will be, but there is another way. The no-chill method is the easiest way to finish it off. Basically, you put the boiling wort into a HDPE cube, sterilising the inside and effectively canning your hot wort for whenever you choose to use it.

Step 8: Ferment

Once cooled, dump into the fermentor, aerate and pitch your yeast. Ferment at a controlled temperature recommended by the recipe, or at very least, the yeast package. Then bottle and enjoy!

Well there you are, eight simple steps to making all-grain beer. Check out some of the recipes on this site or others and go for it!

Happy brewing!

2 comments on “Technique: Brew-In-A-BagAdd yours →

  1. Why can’t the wort be decanted into the fermenter to cool directly rather than putting it into an intermediate container?

    1. You absolutely can put it straight into your fermentor. I did drain mine straight into my plastic fermentor on a several occasions and it gets rather soft. Apart from that, it worked well.

      A word of caution though, make sure whatever FV you are using is heat safe. The last thing anyone wants is a melted plastic fermentor or brew bucket, or even worse a cracked glass carboy and 20L of near boiling wort emptying onto the floor and people around it.

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