Released: My first BIAB

The Homebrew Forum

Help Support The Homebrew Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Sep 12, 2011
Reaction score
Getting Started in BIAB

What and why?
Brew In A Bag (BIAB) is a technique or system for brewing fully mashed, all grain beer in a single vessel. One pot acts as HLT, mashtun and boiler. As the name suggests, a bag plays a very important role in the process.
Brew In A Bag has certain advantages over a three vessel based system, most notably in terms of convenience. While a three vessel system can be made small, collapsible and quite simple to pack away, everything you would ever need to Brew In A Bag will fit inside your pot. While a permanently installed three vessel system in your garage or shed may be quite quick to get a brew on, having a collapsible three vessel system will take a while to set up and check over and Brewing In A Bag will still get you a brew on quicker than either!
Of course there are disadvantages too, a three vessel system allows real flexibility in terms of mash profiles, some complex ones would be really awkward in a Bag Brew, also "big"

The equipment requirement for Brewing In A Bag is significantly shorter and less costly than a three vessel based brewery, you've got two less vessels for a start!

The pot.
Your single vessel can be as simple as just a big pot. I did my first Brew In A Bag with just that " a big pot on the hob, no tap or hop stopper or any other bells or whistles " and it produced a perfect pint. That said, it still produces great beer and it's easier to get the wort out now that it does have a tap and hop stopper!
For single brew lengths (5 gallons) consider a 50l pot. A pretty standard 5% brew will need around 37l of water + the space that the grain takes up and you really don"t want to be getting right up to the top! Before you buy however, consider where your brewing is going: Is BIAB a stopgap to get you brewing all grain beer but you intend to build a full three vessel system? Maybe you want to brew more than 5 gallons at a time (either BIAB or future three vessel)? This was my situation, so I bought a 70l pot allowing me to boil for a 10 gallon brew. As it happens this will allow for a double length 4 or 5% beer Brewed In A Bag, albeit using an offshoot process from BIAB called maxi-BIAB, more on that later.
Three aspects need to be considered together in determining the configuration of your pot:
- Heat source; gas or electricity
- Pot material; stainless steel or food grade plastic
- Draining and filtering
Clearly using gas rules out plastic pots but it also pretty much rules out a bottom draining configuration in a steel pot too " you don"t want to subject sealing washers or dry solder joints to a propane flame. Here"s a handy decision tree to help you decide:


For gas users, you can BIAB on your gas hob with great results but this ties you to brewing in your kitchen and tying up the hob for most of the day, SWMBO may not be too impressed if trying to make Sunday lunch while you brew and you will need a decent cooker hood extractor to cope with the steam from the boil. The alternative is a dedicated burner and bottle. Anything over around 7.5kW should get you a decent boil and you can take your brewing to your shed, garage or garden. If you are going to boil outside you should consider some form of wind break to make sure you get the maximum heat into the bottom of your pot. If you have a big pot, then you could consider a paella pan burner to give more heating area or the more standard square ones.
For electricity users the consideration really is only the number and type of elements to fit to your pot. Much discussion exists on this topic in various brewery build threads, the general consensus though is that two kettle (or other "proper"

One hole in your pot that you really do need is a drain. Siphoning your wort out from your pot is possible but is time consuming and tends to result in a lot of "break material"

Simple side draining hop stopper and tap setup:

Another addition you might consider is a sight glass, a clear polycarbonate tube emanating from near the bottom of your boiler and running up the side giving an indication of the fill level.

Building stainless steel electric boiler is a very useful guide and is applicable to both stainless and plastic vessels.
How to convert a thermo box into a mash tun shows the concepts of fitting a bottom drain, albeit with the additional complication of it being in an insulated pot.

Boilers and pots from: The Malt Miller : The Homebrew Company : Baliihoo

Grain Bag
The only really BIAB-only piece of kit you"ll have to invest in is a grain bag. There are commercial models available but they won"t fit a big pot, you"ll have to befriend a seamstress to get one made. Pure cotton muslin voile is ideal as is the nylon voile used for curtains. Just remember that there is going to be 10kg of wet grain in there at the end of the mash. Seams need to be triple stitched and taped and a drawstring on the top is a must. Tapes running under the bag and crossing in the middle of the bottom panel mean that the pressure on the bottom seams and material is reduced. Simply cut a circle 5cm larger diameter than the external diameter of your pot, then a rectangle with one edge about 10cm longer than your pot is high and the other edge about 5cm longer than the circumference of the circle you just cut: so that's length = (3.14 x (pot diameter + 5) ) + 5.

I've stuck the formulae into a little spreadsheet, just add your pot height and diameter and it works out the size of panels you need to cut. BIABBagCalc.xlsx

Grain bags from: The Homebrew Company : Balliihoo

Mash Paddle
The chances are that you already have a plastic paddle if you came from kit brewing and this is ideal for BIAB, if not, they are inexpensive and readily available.

Mash paddles from: The Homebrew Company : Balliihoo

A decent thermometer is a must. A digital meat thermometer is ideal and one of the "stick it in and leave it in the oven"my mash is too cool"

Thermometers from: The Malt Miller : The Homebrew Company : Balliihoo

Hydrometer and trial jar, refractometer
Essential in all grain brewing to make sure your mash has been efficient enough and to help hit the gravities specified in your recipes.

Hydrometers, trial jars and refactometers from: The Malt Miller : The Homebrew Company : Balliihoo

Turkey baster
Ideal for extracting wort from between the pot and bag for testing! A ladle would also work pretty well but is more awkward.

You"ll need a bucket (your intended FV will be fine) and another vessel of some kind " I use a jam pan.

Various kitchen utensils
Jugs and colanders are really useful too

You need to time your mash, boil and additions. Most brewing software has built in timers I now use Beersmith Lite on the iPad for my brewday timing.

Wort Chiller
Some method of cooling your wort is required. This can be as simple as just leaving your FV to cool in a cold place (outside or a bath of cold water), a dedicated canister for cooling, an immersion or a counterflow chiller.

Wort chillers from: The Malt Miller : The Homebrew Company

Most brewing software can handle BIAB equipment and mash profiles. Personally I chose Beersmith and, with some tweaking here and there, I've got profiles that are starting to work well with my equipment.

Brewing software: THBF Recipes : Beersmith : Beer Engine : Brewmate : ProMash : Brewtarget : Beer Calculus : QBrew and there are plenty more if you have a google.

Wort aerator
A big balloon whisk, electric hand whisk or my personal favourite, the paint mixing paddle and cordless drill!

Your first BIAB
With your equipment all gathered, a shot of courage and a healthy dose of optimism it"s time to crack on and Brew In Your Bag. Here"s a simple recipe to get you started, based in fair part on Graham Wheeler"s Hooky Bitter Recipe (and I thoroughly recommend his book "Brew Your Own British Real Ale"

Rookie BIABitter

3.25kg Maris Otter
0.36kg Flaked Maize
0.24kg Crystal Malt (135.0 EBC)
0.03 kg Black Malt (1300.0 EBC)

Hops etc:
28.00 g Challenger [7.00 %] @ 90.0 min
5.00 g Irish Moss @ 10.0 min (rehydrated in wort 15 mins before addition)
10.00 g Fuggles [4.50 %] @ 10.0 min

1pkt Nottingham or similar

Dry Hops:
20.00 g East Kent Goldings [5.00 %] Dry Hop 14.0 Days

You can make life easy on yourself by just ordering the whole recipe from those suppliers happy to do so.

Both The Malt Miller and The Homebrew Company have agreed to supply the recipe in kit form.

Note that the The Homebrew Company will provide a standard crush and so the first step of the mash time should be increased by an additional 30 mins to ensure maximum efficiency. They will also supply a whirlfloc tablet instead of Irish Moss. There is no rehydration required with these, just throw it in where the walkthrough tells you to add the rehydrated Irish Moss.

The Malt Miller will, if you ask, crush the grain finer. By the nature of using the full volume of water to mash, the enzymes which convert the starch to sugar are more dilute and so have a harder job. A finer crush allows those more dilute enzymes easier access to the starch. We also don"t have the problem of a set mash from the crush being too fine. They will be supplying the hops in 100g vac-packs which means that you will have a small collection of really classic British hops with which you can plan your next BIAB, when you have taken out what you need, just squash the bag down as best you can, seal it in a freezer bag and keep in the freezer until your next brewday...

Once you have all your ingredients, make yourself a brewsheet. Just a cribsheet of all the steps, timings, temperatures and volumes that are going to be important, this will keep you on track and give you somewhere to note down your own actual readings against your expected ones. You are unlikely to nail every one first time

...if you have brewing software, you can likely plug the values for the recipe in and it'll generate one for you. If not, I've created a spreadsheet pre-populated with the recipe and some handy defaults (based on my kit). There are instructions in the spreadsheet, read them through and either use it on your computer as you brew or print it off and write in your measurements as you go. BIAB Brewsheet.xlsx

Ingredients and brewsheet ready to roll:

also the volumes given here are for my 70l pot on gas, some searching around should give rough figures to get you started with your setup " or ask, there may well be someone already BAIBing with similar kit. You can actually work out what a sensible starting figure should be, take a look at the Addendum at the bottom...

The Mash
So, fill your pot with 35.5l litres of water and add a crushed Campden Tablet to neutralise any chlorine and chloramine in your tap water. Other water treatments for now are just an additional complication that you really don"t need wait until you have 20 more BIABs under your belt before you even think about it. Set your thermometer"s upper alarm to 70 degrees Centigrade and dangle the probe in. Turn on as much heat as you can and start to organise everything else you"ll need " do it in order, have your grain ready, your paddle etc. Stir your pot now and then just to be sure the liquor is the same temperature throughout, do it more regularly as you approach your strike temperature of 70 degrees.

Also as you get close to strike temperature, get your bag in the water, pull the opening of the bag over the lip of your pot and pull the drawstring to keep it in place. You"ll have to move your thermometer probe to inside the bag too.

As soon as you have 70 degrees C, turn off the heat and start to dough in. A big jug in one hand and your mash paddle in the other and stir as you pour in your grain rather than dumping it in and trying to stir out the lumps. You can't over-stir a BIAB, so really go for it, we don"t care if our grain gets waterlogged! When you are done, put on your lid and check time and temperature, note them both.

Grain all doughed-in and mashing:

Change your thermometer alarm settings, max should be 68 degrees C and min 65 degrees C. The actual temperature you are looking for is 66.7C but just keeping it in that range should be fine.

The grain should have taken the temperature down to about 67C. You now have a choice. You can either insulate your pot so that it doesn't lose heat over the next 90 minutes or you can just warm it up whenever the alarm goes off. As I use gas and a cotton bag this is just as simple as turning on the burners and stirring until I get back up to 67 or 68 degrees. I"d probably worry about nylon bags and electric elements though so if that"s your setup maybe go with the duvets/hot water cylinder jackets to keep the heat in.

Give your grain a good stir now and again remember the low concentration of those enzymes, mix them up a bit to get the best coverage and the most out of your grain. When 90 minutes is up, fire up your heat " again, be careful with electric elements (maybe you could pull more of the bag down the outside of the pot to make sure it is away from them) until you reach 76 degrees. Maintain this temperature for 10 minutes. This is the BIAB equivalent of a Mashout which is designed to let the amylase which makes long chain unfermentable sugar from starch continue to work but prevent the other amylase which breaks it down to fermentable maltose from doing its job thereby giving body and mouthfeel to your beer.

Once that ten minutes is nearly up, get your bucket ready and man up! This is where things get hot, heavy, sticky and sometimes a bit painful
Put your colander in the bottom of your "other"

When time is up, take the thermometer out then loosen the drawstring and unhook the front of your bag from the pot. Then quickly, without unhooking the bag from the rest of the pot first, pull the drawstring closed. Now slowly start to lift the bag out of the pot. Lots of wort will be trapped so you will have to wiggle, jiggle, bounce and do whatever you can to keep the wort running. Just don"t squeeze or you run the risk of releasing too much tannin from the grain husks.

When the flow slows down and you feel the burn in your arm muscles transfer the bag to the colander and take a rest. Get the heat on to full to get the boil under way. As the wort heats, periodically take the bag from the colander and tip the collected wort into the pot then return the bag to the colander.

The Boil
Now everything is just the same as the three vessel brewers do. Be sure to understand how your wort chiller of choice works as you will have tasks to perform towards the end of the boil to prepare it.

Just before you reach the boil, somewhere around 96 degrees, add the first batch of hops and measure your pre-boil volume and gravity, note them. Hopefully you should get around 33 litres @ 1.032.

90 minute hops in just before the boil starts and a good rolling boil:

Once you are boiling, sanitise your FV and all your fermentation bits and pieces, lid and airlock and bung and what have you. Prepare your chiller if you have such a thing.

After 65 minutes from when your wort actually starts to boil, use your turkey baster to add half a mugful of wort to your Irish Moss to rehydrate it.

After a further 15 minutes chuck the mugful of wort and Irish Moss into the pot along with the second batch of hops. If you are using an immersion chiller, you should put it in now but don"t turn the water on. If you are using a counterflow, you could sterilize the thing by running some hot wort to your FV and tipping it back into the boiler " you would ideally want to re-sanitise your FV.

Boil for a further 10 minutes and take another sample, chill to around 20 degrees and measure your gravity and your volume. Hopefully you now have about 27 or 28 litres in your pot @ 1.040.

Ten Forty. BOOM!:

If you are over gravity but under volume the chances are your efficiency is right, just add some water to bring your volume up and your gravity down. If you are over volume and under gravity then again, your efficiency is probably right but your boil off rate is wrong change it in your software next time out. This brew however you can either just ferment it and get a weaker beer or keep boiling. This will affect your 10 minute hop addition though, you would probably want to add a bit more Fuggle once you are closer to the 27l. Another alternative in this case is to use malt extract to bump up the gravity, just dissolve it in a little hot water and add it. If you are up on gravity but right on volume then you are more efficient, just ferment it for a stronger beer or you could liquor back to the right gravity and get more beer at the right strength. If you are on gravity but under volume, again just make do with less beer at the right strength.

Chill and Ferment
Next step is to get your wort out of the boiler and chilled. If you haven't used an immersion chiller you will have the "cold break material" in the collection vessel. You could rack from the collection vessel to your FV to remove this debris once cool, it should ensure a clearer beer.

The gunk that's left after the boil:

Once you are down to the required pitching temperature of your yeast, you need to aerate your wort (you want to see a really good foamy head), pitch your yeast, add your lid and airlock if you use one and tuck it up at 18 degrees to ferment.

After 5 or 6 days rack to a clean FV and add the final batch of hops, then leave it alone for a further 10-14 days.

Bottling or kegging is the same as you would for kits or extract brews you may have done, in this case use around 4.7g/l for a nice aley-but-lively carbonation.

Leave it in the warm until the bottles clear again. It should come into drinking condition about 3 weeks after that.


Calculating mash water volume.
You need to consider several things, some of which are specific to your equipment.
- The volume you want to finish with
- The amount of water the grain will absorb
- The amount of water the hops and remaining gunk in your boiler will hold
- The amount of water that will be boiled off

Notice that there is no allowance for deadspace. That will just be rolled up with the hops and trub and gunk.

Here's how we get to the 35.5l:

I want 23l in my FV.
3.88kg of grain once drained sitting on a colander will contain 2.37l of water (610g of water per kilo of dry grain).
38g of hops will hold 1.14l of water which is quite incredible! (300g per 10g of hops)
Although with a pure water run, my boiler only leaves one litre, used in anger it is much much more. 3.8l there.
Then boil off. My 70l pot boils off 3.5l per hour. That's 5.25l This varies with the surface area of your pot, the intensity of your boil, the atmospheric conditions etc.

Add them all up and we get 35.56l

So as your start point:

Start Volume = VolInFV + (grainKGs x 0.61) + (hopsG / 10 x 0.3) + trubAndDeadSpaceLitres + (boilHours * boilOffRate)

Guess your trub and dead space as the volume left when you drain clean water plus the area of the bottom of your pot in square cms * 0.00181

trubAndDeadSpace = trueDeadSpace + (3.14 * (potDiameterCms / 2) * (potDiameterCms / 2) * 0.00181)

I've worked all that calculation into an Excel brew sheet to make life easier if you and equations just don't get on. Get the BIAB Brewsheet.

Measuring volume.
Measuring your initial volume is easy, you have a jug, just add it litre by litre and keep count. Alternatively, if you have accurate enough scales you could add as many kilos of water from a hose from your tap as you need litres. Just remember that lifting a pot with 36kg water in it isn"t for the faint hearted!
If you have a sight glass things get really easy, calibrate it once and just add water until you get to where you want to be.

But what about pre- and post-boil volumes if you don't have a sight glass? It"s maths time! Measure the internal diameter of your pot. Note it down. Add, using a jug, your starting volume then measure the height from the water surface to the top of the pot.

Calculate the unused pot volume. So that's the height from the surface to the top multiplied by the diameter divided by two then squared multiplied by Pi. e.g My pot is 44.5 cm diameter and if I had 21.5 cm of space at the top, the calculation would be:

Empty volume = 21.5 x (44.5 / 2) X (44.5 / 2) x 3.14 = 32644 cubic cms.

There are 1000 cubic cms to the litre so that"s 33.241 litres.

If I had added the 35.5 litres of water then that means my pot holds 68.92l

"Why don't you just do that for the whole height of the pot?"

So during my brew I can do the same calculation as above then subtract the volume from my total capacity of 68.92l:

Wort volume = Pot Volume " ( ( (diameter / 2) x (diameter / 2) x 3.14 ) / 1000)

The other method for in-brew measurement is to build yourself a calibrated dip-stick. To do this all you need is a suitable thin stick and some time before your brew to add a litre of water, dip the stick, mark it, add a litre of water, dip the stick, mark it, add a . You get the idea.

Taking Notes.
Really, write down as much as you can! It helps you understand your kit and makes planning future brews more accurate.

Recalculating your initial water volume.
No doubt your pre- and post-boil and in-FV volumes from your first BIAB were wrong. Hardly surprising, everyone's kit is different and will have different properties.

If you have taken proper notes you will know your pre-boil volume. Subtract that from the total you started with to get your total grain absorption. Divide by the total weight of dry grain to get your new grain absorption rate.

Next you know your post boil volume. Subtract that from your pre-boil volume and divide by the number of hours you boiled for. There's your new boil off rate.

Next you knoww your volume in your FV. Subtract that from your post-boil volume to get your new hops + deadspace + trub loss volume. Subtract the hop absorption from that to give your new dead space and trub constant volume.

Use these figures when you calculate your next brew and you should get a lot nearer. Bear in mind though, that big brews and mega-hopped brews will likely throw your rates and constants out a bit. Just beware and remember to take notes!

Again, I've worked that into the BIAB Brewsheet too, just fill in all the values on your brewday and it'll work out all the stuff that wasn't quite right.
Oh, and thanks for letting me in! ;)

That's just the text for now - I'll be formatting and adding pictures over the next couple of days. Do let me have feedback and if you have any pics that might be useful, please post me a link!

Counterflow, plate and immersion chillers for a start - no chill cubes too. Electric boilers suitable for BIAB, gas burners both the square type and the paella pan ones.

bottom drain + false bottom, side drain + false bottom...

Basically anything I don't have in my set up really which is stainless, gas hob, side drain, single tube copper hop stopper, no chiller at all.


wow, that's a lot to go through :clap:

First thought - " we also don’t have the problem of a set mash from the crush being too fine." - do you mean a stuck sparge??

I wonder if the step by step walk through the brew day would work better for people if it contained some simple rules - e.g. for calculating the initial volume of water ? :hmm:

Keep working at it - it's already looking like it'll be a deeply popular How To :cheers:
BigYin said:
First thought - " we also don’t have the problem of a set mash from the crush being too fine." - do you mean a stuck sparge??

Aye, that's exactly what I mean! We don't worry about those in bag brewing. :)

I did think about it, but then thought twice because I haven't gone to the lengths of working it out... Shouldn't be too hard to do... let me have a think...

BigYin said:
t's already looking like it'll be a deeply popular How To

Thank you, I hope it will, there is a lot going for BIAB as I've discovered. :thumb: I we get more people brewing really good beer then that can only be a good thing in my book!
That looks excellent :clap:

Here's a suggestion: - you mention chilling but I'd suggest splitting certain bits that can be the same for different techniques into "how tos" in their own right and then linking to them. For example, a "How to chill your wort" and a "How to aerate your wort" etc which are separate for people who just want to know that; in your main text you just say something like "next you chill the wort - see link for how to"

What do you think? :hmm:
Yeah, it makes sense, particularly as that isn't exclusive to BIAB. Watch this, or rather some other, space...
Great work Calum, I think martins idea makes sense, a lot people may already know how to cool etc. and a link will help any one who doesn't.
I also think it is a good idea, like having chapters which you can link with clickys.

By the way when is the book coming out :lol: :lol:
graysalchemy said:
I also think it is a good idea, like having chapters which you can link with clickys.

By the way when is the book coming out :lol: :lol:

:hmm: Maybe another day... month... year... I'll add it to the crazy list of stuff to do! :lol:
Here's a suggestion: - you mention chilling but I'd suggest splitting certain bits that can be the same for different techniques into "how tos" in their own right and then linking to them. For example, a "How to chill your wort" and a "How to aerate your wort" etc which are separate for people who just want to know that; in your main text you just say something like "next you chill the wort - see link for how to"
Great idea, saves a lot or repetitive work too, could embed it and/or glossary it.

I agree entirely.

I'll strip the BIAB back to just the equipment, recipe and walk through with obvious placeholders for where the future cross linked articles will be linked. Maybe a link to a sensible search result in the forum for now? e.g. this.

Then I can write dedicated How To's for those in future. Whaddaya reckon?
No get them all written now :lol: :lol:

I'm sure you can find the time :whistle: :whistle:

Voosy's got a whole list of how to's that need doing :lol: :lol: :lol:
:lol: :tongue:
Maybe a link to a sensible search result in the forum for now? e.g. this.
Keep this to yourself but we're in the process of potentially making the search facility more user friendy which may or may not have implications to your linking. I think it would look messy for you to have to say link 4 types of cooling method individually, there's got to be a better way of doing it :hmm:
I could cheat and use google with the "site:" directive rather than sticking with the phpBB search, that way I could get more targetted results...

Mum's the word... :thumb:
Vossy1 said:
:lol: :tongue:
Maybe a link to a sensible search result in the forum for now? e.g. this.
Keep this to yourself but we're in the process of potentially making the search facility more user friendy which may or may not have implications to your linking. I think it would look messy for you to have to say link 4 types of cooling method individually, there's got to be a better way of doing it :hmm:

The better way of doing it is to have a specific how-to even if for now that has links to other specific posts that talk about each method in details. As and when time allows, the main how-to can be updated.

calumscott said:
I could cheat and use google with the "site:" directive rather than sticking with the phpBB search, that way I could get more targetted results...
Mum's the word... :thumb:

Calum, we're currently experimenting with a Google custom search embedded into the forum so no need to use the site: approach and navigate away from the forum. By the time your how-to is complete, we will probably be ready to go live with it.

Latest posts