Brew in a bag is the perfect way to start all grain brewing – the techniques are simple and the results are great.
This detailed guide explains how to do it.
Brew in a Bag History
Brew in a bag (BIAB) originated in Australia and was initially considered controversial. Many brewers believed it produced inferior beer to all grain methods. However, nowadays it’s use is fairly widespread.
The innovation of BIAB was to combine the benefits of all grain brewing, such as greater choice of ingredients and more control over flavour, with the minimalism of extract brewing, where everything takes place in a single brew pot.
Its simplicity is ideal for beginner brewers who can’t wait to start all grain brewing.
Traditional all grain brewing involves many steps such as steeping malt in a mash tun (often a modified ice chest) before rinsing multiple times in a process known as sparging.
Calculations are performed to ensure that the temperatures and quantities of water and malt are in harmony. The wort (water with malt sugars) that is extracted at the end is boiled and fermented.
That this complicated procedure was developed before one so simple (and effective) is bizarre. Nevertheless, that is the accepted history of the subject.
Equipment For Brew In A Bag
If you already brew with beer kits or malt extract, you should have most of the brewing equipment needed for BIAB.
In addition to the basic kit you’ll also need:
- a bag
Yes. The only other item you’ll absolutely need to get is a bag made of any light weave, strong fabric. Mine is from a material similar to linen:
The most economical bag is the one you make yourself. In fact, as BIAB is still finding its feet you may struggle to buy a made for brewers bag.
If you opt to make your own, when selecting a fabric choose a strong one. By this I mean that it is able to hold 10-15 kg without breaking. The fabric will act as a filter, holding grains while liquid drains quickly through it. A popular material for many brewers is voile.
An oft-cited limitation of brew in a bag is the inability to brew strong beers due to the difficulty of lifting large amounts of grain from the brew pot. A strong handle will go some way to alleviating this problem.
(Some brewers rig pulley gear to lift the bag from the pot but this is beyond the ambitions of my minimalist setup.)
A good discussion of brew in a bag in general can be found in this article, for anyone interested in finding out more.
Depending on your equipment setup you might consider getting a false bottom for your boil pot.
During the BIAB mash stage, you leave malt (inside the bag) standing in the brew pot, which is filled with hot water.
Malt near the bottom, that is close to the hot stove, will burn unless steps are taken. Many manufacturers supply made to measure disks that fit snugly.
However, a stainless steel colander works equally well:
The perforated false bottom lifts the grains from the bed of the brew pot but allows water to circulate freely through it.
Brew In A Bag In A Nutshell
A quick guide to brew in a bag:
Malt is put into a bag and soaked in water of a pre-determined temperature.
After an hour or so the bag is removed and drained, leaving behind a sugary liquid known as wort.
This is boiled with hops that are added to contribute bitterness, aroma and taste. After cooling, the wort is aerated and yeast are added before the wort is fermented for around two weeks.
The resulting beer is bottled or kegged.
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A Typical Brew Day
The following photos and instructions describe use this English bitter recipe as an example. The steps are the same for any recipe.
1. Prepare The Brew Pot
Fill the brew pot with the water. Unlike with all grain brewing, you will mash with the full boil volume of water.
Unfortunately there aren’t any hard and fast rules about how much water to add, but as a general rule of thumb you’ll need 30 – 50% more than your target volume.
Water is lost to the grains, to evaporation, and to the hop residue that’s left in the pot. A well-draining bag will reduce loses, as will brewing lighter beers (with less grains), and using an efficient stove.
After a couple of brews you’ll have an idea of your own setup’s performance and can adjust the water quantities accordingly. For the English bitter recipe I use 21 litres of water to yield 14-16 litres of beer.
Heat your water to 1°C more than the target mash temperature of the recipe, to allow for cooling caused by the grain addition. When it’s ready, line the pot with your brew bag.
2. Add The Malt
Weigh the malt according to the requirements of the recipe.
Take care not to introduce excess air when adding it to the brew pot, or oxidation will occur and cause off-flavours.
Let the grains gently sink into the water. If you’re using finely ground additions (such as the polenta in the example bitter recipe) put that in last so the larger grain hulls can act as a filter at the bottom of the bag.
Stir the mash, again very gently, until the grains are submerged and wet.
The other purpose of stirring is to ensure uniformity of water temperature. You’ll find that the mixture is much hotter towards the bottom, and that it’s difficult to truly measure its temperature.
If it’s cooled significantly during the previous stage (quite likely) add more heat to bring the wort back to temperature. Put the lid on and leave according to the mash schedule, 70 minutes in the example recipe.
When the time has elapsed lift the bag from the wort and drain, holding it close to the beer’s surface and taking care not to splash and introduce air.
When the wort starts to drip rather than pour from the bag I usually drop it into the fermentation bucket (fitted with another colander style false bottom) so it can self-drain for twenty minutes or so.
You’ll usually get another litre or two of wort by doing this, which you can pour back into the brew pot.
You’ve made the wort. If you’re familiar with extract or beer kit brewing, you’re at the point you would be after adding the tin of malt. The following steps should be familiar.
Bring the wort fully to the boil before beginning the hop additions. Once it’s vigorously bubbling you’ll see a yellowy foam form on the surface. These are proteins joining together and leaving the liquid in a process called the hot break.
Follow the schedule of your recipe to add the bittering and flavouring hops.
5. Cool the Wort, Quickly
A key factor in getting a clear beer is how quickly you cool it after boiling. This stage is the cold break, where more proteins are forced from the wort. I use a bathtub filled with ice bottles for a cooling, but if you have one use a wort chiller.
While the cooling down takes place, prepare the yeast. The example recipe uses dried yeast and this needs to be rehydrated in around 200ml sterilised water.
6. Pitch the Yeast
Once the beer is cool transfer it to the fermenting bucket.
It should be close to fermentation temperature, which for most people is room temperature.
Pour it several times between the bucket and the brew pot to aerate it. This will make it easier for the yeast to multiply and ferment the beer.
This is the only time when air should be in contact with the wort.
Of course, sanitise the fermenter before adding the beer.
Unless you used a hop bag, it’s a good idea to pass the wort through a sieve the first time it’s poured into the bucket. Otherwise, the hop and hot break debris will remain in the beer.
Although it shouldn’t affect the taste too much (unless you leave it fermenting for several weeks), it could cause problems during bottling if the gunk is sucked through the siphon and clogs it.
Put the lid on the fermenter and leave for around two weeks before priming and bottling.
Here are a few more things to consider as you’re trying brew in a bag for yourself:
- The temperature is hard to control. Be careful not to overheat the water because it will cool very slowly, and unwanted tannins will be extracted from the malt if it’s too hot. You can always add more heat if you undershoot.
- Drops of wort dribble everywhere when you remove the bag from the pot. Put something down to protect your stove if you’re worried about that.
- Because of the relatively unrefined filtering technique brew in a bag beer can be a bit cloudy, especially if you wring every last drop of wort out of the grains. To counter this add whirlfloc or Irish moss for the last ten minutes of the boil.
- The bag can get extremely hot and heavy when full of water so take care with your hands. It should be big enough to sit comfortably in the water while leaving enough dry fabric for you to grip.
If you have any questions, leave a comment.
Otherwise, try this simple brewing technique and enjoy!