What is Brew in a Bag or BIAB?

What is BIAB

For those just starting out, brew in a bag or BIAB is a method of brewing that allows you to brew all grain beer in a single vessel. Traditionally beer has been and still is brewed in commercial breweries using several vessels called tuns, kettles and tanks, depending on their use and purpose. Home brewers for the most part have used scaled down versions of these with the most popular being the three vessel system. Typically the all grain home brewer would employ a cooler for a mash tun, an electric kettle or large pot for a hot liquor tank and another large pot as a boil kettle, and this system would require the brewer to move the liquor from the liquor tank, to the mash tun and then onto the boil kettle and finally into the fermenter after cooling. BIAB on the other hand allows you to mash and boil in the same kettle thus saving equipment and extra complexity. BIAB brewers can even utilise a single vessel and brew with either no sparging or reduced sparging by heating most of the liquor in the kettle before mashing in and then using a regular kitchen kettle to do a light sparge or rinse of the grains at the end of the mash. Then once the mash and sparge are done you can empty the grain bag into a recycling bin or a compost pile, give it a rinse and clean and it’s good for the next brew and you can even do this while your kettle is slowly coming to the boil to save time.

Types Of BIAB

Whilst BIAB is the method, there is more than one way to practice this brewing method depending on the equipment you are using and BIAB is more than just a nylon grain bag. In fact BIAB can also include non-bag single vessel brewing as these systems typically use either a malt pipe  which mimics a mash tun or a grain basket which serves a similar purpose as the nylon bag. Typical single vessel systems with a malt pipe include the brewzilla and grainfather all in one brewing systems and others like them. These systems use a solid malt pipe which is a stainless steel tube with a removable mesh bottom disc that slides inside the brew kettle and contains your grain for the mashing and sparging processes. Then when you’ve finished you lift it out completely and your kettle is now ready to boil the remaining wort. 

During the mashing process this malt pipe mimics a mash tun by allowing the wort to pass through the grains from the top to the bottom of the pipe where it can then be recirculated or pumped back to the top of the mash. Another variation of this system is the newer brew in a basket system which is becoming more popular now with a number of new brands entering the home brew market. The difference with these systems is the solid walled malt pipe is replaced by a stainless steel mesh basket that allows water to move through the sides of the grain bed and not just top to bottom, and this more closely mimics the nylon bag of traditional BIAB. A solid basket would allow you to get a proper grain bed like a malt pipe for sparging but also allow liquid to strain through in all directions like a nylon bag. It will be interesting to see in time how the grain basket compares to the malt pipe system in regards to mash efficiency and wort clarity. These non-typical BIAB systems can also be used either as single vessel systems with varying degrees of sparging employed in the process from a large kettle or secondary pot and cook top, or they can also be used with a second kettle doing the job of a hot liquor tank and be in effect two vessel brewing systems.

Traditional BIAB

And finally the original BIAB method that most people understand as brew in a bag utilises a nylon mesh bag that goes into and lines the inside of either a large pot or an electric kettle. With this system most people will typically insert the bag once strike temperature is achieved and use clamps to keep it in place while they pour in the grist. This way you can make sure that the grain is fully mixed with the strike water to avoid any lumps or dough balls. You could also fill the grain bag with the dry grist and insert it into the strike water like a gigantic tea bag but you will find that if you don’t stir the grain, you will like get dry pockets and dough balls that won’t mix in properly within the initial saccrification period of the mash. The beauty of this system is that it’s much easier to rinse and clean a grain bag than it is to clean a separate mash tun or even a malt pipe with its mesh screens, and a grain bag can be folded away after use and packed in even a tiny container thus taking up no extra space in your brewing area or shed.

The downside of brewing in a nylon bag is you don’t get a solid grain bed which is much easier to sparge or rinse than grain in a grain bag. Malt pipe or brew in a basket systems allow you to easily sparge with the pipe or basket partially lifted out of the wort, whereas many people who use nylon bags find that they need a second large container and a sieve to be able to rinse the grains in the bag properly. You will also have to deal with differences in your mash efficiency when you BIAB and often when doing BIAB for the first its not unusual to get a loss of efficiency of several points or more. This likely happens due to both the lack of traditional sparging and the size of the grain crush. Typically most grains are crushed to a size that suits traditional mash tuns and sparging techniques, and often brewers will mill or crush their grain slightly finer to compensate for this loss of efficiency. Some brewers though will also compensate by simply adding more grain to the grain bill to begin with and accepting a loss of efficiency as a given. 

And as for traditional sparging techniques, most of these are designed to slowly and thoroughly rinse the grains of of their residual sugars while not disturbing the grain bed, and seeing as the grain bed in BIAB is lifted out of the wort at mash out and compressed in the process, these methods wont work as well. So some BIAB brewers simply do whats called a no sparge mash where they will mash with the full volume of liquor and lift and drain the bag only while they begin the heating process for the boil. Others will do a mini sparge or rinse where they will mash with around 80% of the liquor and rinse a little at the end. 

I personally use the rinse or mini sparge method the most and i will typically do quite a thin mash with the majority of the liquor being in the mash in the beginning. But I also use an external pump to recirculate my wort during the mash, and the pump has two benefits for me, firstly it stabilizes the mash temperature better by recirculating the wort which stops dramatically different temperature zones from forming in my mash. Before I used a pump to recirculate it wasn't uncommon to see my mash temperature overshoot by 4 degrees Celsius when the heating element kicked in during the mash. And secondly I believe i have gotten a boost in my efficiency by recirculating the wort during the mash. At the moment i'm still undecided about how much I've gained but I hope to do a side by side test in the next few months to find out!

Why BIAB?

So why would you choose to brew in a bag over any other type of brewing system? Well so far I’ve given some answers already but for the new brewer just starting out in brewing or the brewer who is moving from extract brewing to all grain here is a list of reasons why you would consider BIAB as your next brewing system

1. BIAB is cheaper! That’s right, it’s probably the cheapest way to get into all grain brewing and you can get setup for as little as $200 for a full sized system if you already have some brewing equipment from fermenting extracts, or roughly $300 for everything, including a fermenting vessel and all the pieces of gear you need for you brew day. Plus if you wanted to start small you also have the option of buying a small batch kit that comes with everything you need for around $120-$150! Now if you decided to buy an all in one electric system with either a malt pipe or a grain basket then you are going to pay a fair bit more and prices for these systems range from $400 right up to $1500 or more depending on the brand and perceived quality of the unit you are buying. But even if you are buying a more expensive $1,500 system your still cheaper that a $3,000 three vessel system which is the fairest comparison.
2. BIAB has less vessels, and therefore less to clean, less space to store it and less that can go wrong. These statements are all true depending on the type of BIAB system you buy but you are still dealing essentially with a single vessel system so in the end you only have one vessel to clean and one vessel to store etc.
3. Almost any large domestic or commercial electric kettle can be turned into a single vessel brew system with the addition of a nylon bag! That’s right, you can use a 35L commercial office urn if you had one or you can use any number of electric kettles that are sold by many different home brewing stores as hot liquor tanks. The benefit of kettles designed to be hot liquor tanks for home brewers is that they are already setup to be able to heat water to specific temperatures which is very hand for mashing. Most commercial electric urns are only designed for boiling water for coffee and tea so ha e more limited temperature options if any. And you will even find that some brands of electric kettles made for home brewers are actually cut down versions of their own all in one brewing systems so they share the same dimensions and have a basic temperature control to replace the more complicated controller used by all in one brewing systems. This means that you can often purchase accessories for the brewing system that will fit in the kettle like a false bottom so you can heat it with a nylon bag in place!
4. Most BIAB systems are self made or made with interchangeability in mind. That means you create the system yourself using the parts that you source from your home brew suppliers. The benefit of this is you can get all the parts you need from the cheapest suppliers and mix products and suppliers in the process. You can also build a system with better or larger parts and parts that up-gradable or replaceable very easily. So when you have a pump issue or a hose issue you dont have to pull apart you machine to fix it! You can also buy pre-made systems that have interchangeable parts that you gives you the benefit of being able to replace or upgrade as needed or you can also buy systems that have everything built together in one product that requires no thinking or assembly at all. But remember that all in one systems with everything built in often have smaller and less powerful pumps that block easier and if something breaks inside you could be up for expensive shipping and repairs!
5. And lastly to add to number 4 you can build your own custom system! This is definitely something that a lot of home brew enthusiasts enjoy and i'm definitely in the camp of liking to make my own system. I've personally utilized an electric brewing kettle with a nylon bag and an external pump setup that I added myself to recirculate my mash and this gives me the ability to further stabilize my mash temperatures and also to move the wort as needed for a cooling system.

So there you have it, I hope I've given you a good idea what BIAB is and how it can suit you as a home brewer. For many of us BIAB will be a great starting point for our adventures in all grain brewing, for some of us it will be a system for life while for others it will be just one of the stops along the way. Whichever it is for you, if any, I hope it serves you well.

Happy Brewing!