If you went through corporate training in the 1990s or saw the demonstration reel for the Video Toaster, you’re familiar with the term “paradigm shift.” Brew in a bag (BIAB) is a paradigm shift for all-grain homebrewing — a new way of thinking that is a break from the past.
Traditional thinking for all-grain brewing says you need three vessels: one to use as a hot liquor tank for heating water, another to use as a mash tun where wort (unfermented beer) is created, and a third where the wort is boiled and hops are added. BIAB calls for just one vessel – your brew kettle, where all of the above functions will happen.
As you might expect, the key to the whole equation is a bag. In my case, I use a nylon bag that I purchased from my local homebrew shop that is sold for this specific purpose. Others make their own out of material such as voile. I’ve also heard from brewers who buy paint strainer bags from the local hardware store. The key is that the bag is big enough to line the kettle, strong enough to hold several pounds of wet grain, and safe in heated water. In other words, it won’t leach any hazardous or unsavory chemicals into the wort.
Traditional All Grain Brewing
Let’s step back for a second to look at how traditional all-grain brewing works, so we can compare and contrast.
First, malted grain, usually barley, is milled in a roller mill that crushes the kernels and opens them up to the water of the mash. The grain is added to hot water in a mash tun, which has a screen of some sort in the bottom to help filter the wort and a spigot to collect it. The mash rests for an hour or so at a temperature friendly to enzymes that turn starches into sugars. Yeast will later turn those sugars into alcohol and carbon dioxide through fermentation.
After the mash rests, the wort is recirculated from the bottom to the top of the mash tun until a filter bed of husks is established. Then, the wort is drained into a kettle for boiling. At this point, brewers have a choice. They can begin to add hot water at the top of the mash tun to replace the wort coming out of the spigot and rinse (sparge) sugars from the grain (lautering). This is called continuous sparging or “fly-sparging.” Alternately, they can let all of the “first runnings” run out of the mash tun, close the spigot, and add all of the sparge water at once. This is called “batch sparging.”
One of the advantages to BIAB is that you never have to worry about a stuck sparge. If too much wheat or rye is used, for example, or if the grain has been milled too aggressively, the mash could become gummed up in a mash tun, resulting in the wort being trapped in the gooey mess. To combat this, all grain brewers often use rice hulls to keep the wort running. But sometimes even rice hulls are not a guarantee.
After the wort is collected, it is boiled. Hops and other ingredients are added. At the end of the boil, the wort is chilled and transferred to a fermenter, where yeast is added (pitched).
The BIAB Process
For BIAB, all of the water to be used in the brewing process is added to a brewing kettle. This includes the “strike” water – water used in the initial mashing, sparge water – water used for rinsing sugars from the grain, and an amount of water to compensate for the liquid that will be absorbed in the grain after mashing. The water is heated to a temperature above what is needed for the saccharification rest, which is where starches are converted to sugars (149˚F – 158˚F or 65˚C – 70˚C). That strike temperature will come down when the grain is added. Online calculators are handy for figuring out what the strike temperature needs to be.
The bag is added to the kettle to line it, and the grain is stirred in. The temperature is checked again to ensure the proper temperature has been reached. Then, the mash rests for an hour or so while the enzymes do their jobs.
The resulting mash is much thinner than traditional all grain brewers are used to. This may scare some people because thin mashes are said to contribute to thin beer. However, I have brewed low gravity beers with water-to-grain ratios as high as 3.75 quarts per pound with good results.
After the mash rest, the bag is simply removed and hung to drain above the kettle. I use the strut of a ladder as a handy place to hang the bag, but others go so far as to hang a pulley system in the ceiling of their garage.
Some may fear astringency from squeezing grain bags, but I have no such fear. In fact, I have invested in a pair of rubber gloves designed for BBQ guys who handle hot racks of ribs and pork butts. The gloves keep my hands nice and cool as I squeeze the wort from the bag. [Insert your joke about bag squeezing here.]
If you’re a traditional BIAB brewer, that’s it. You’ve collected your wort, and you’re ready to proceed to boiling as in a standard all grain batch.
After getting feedback from listeners to Basic Brewing Radio, I have added a sparging step to my BIAB process. Instead of adding all of my brewing water initially, I reserve a gallon-and-a-half or so for sparging in a second smaller pot. During the mash rest, I heat that water to around 170˚F (77˚C). After draining the bag, I put it into the second kettle with the sparge water. I stir it a bit to rinse the grain, then remove the bag for draining (and squeezing). I haven’t evaluated how much this improves my efficiency, but it makes me feel better. And isn’t that what it’s all about?
The first benefit that BIAB brings is a reduced cost of entry into all grain brewing. You don’t have to invest in a mash tun or three-teir system to brew great all grain beer. You still can, if you want to, though.
You’ll save time and effort with BIAB. I find my brew day is quicker because I’m not having to preheat and wash the cylindrical cooler that I use as a mash tun. Just a quick wash and ring out, and the bag is done.
You can mill more aggressively with BIAB. No worries about stuck sparges, so you can close the gap a bit on your grain mill, possibly leading to higher efficiencies of pulling sugars from the mash.
New beer styles are open to you through BIAB. I have brewed 100% wheat and even 100% rye beers using the bag that would have been completely impossible in my traditional mash tun. Again, no worries about a stuck sparge.
There are a couple of things that I don’t like about BIAB that I see as fairly minor. First, there seems to be more trub in the kettle with BIAB batches. I think this must have something to do with the fact that the wort doesn’t go through the filter bed of a traditional lauter and sparge. However, this can be dealt with by compensating with higher pre-boil volumes.
Wet grain is heavy. The older I get, the less I want to deal with lifting up heavy weights. So, for higher gravity beers, I still use my traditional mash tun setup. I’m also too lazy to rig a pulley system in my garage ceiling.
If you’re not careful, bags can melt or scorch. The only time this has happened with me is when I was using a smaller kettle and the bag draped too close to the flame on the outside of the kettle. If you plan on adding heat during a mash, lift the bag out while the fire is on. Or, add a rack of some sort in the bottom of your kettle to keep the bag off the hot metal.
When I first heard about Brew in a bag, I was a skeptic. However, once I brewed my first batch, I was impressed and convinced that BIAB is here to stay as a legitimate brewing technique. Since then, I have brewed many BIAB batches, including a Pilsner that required a cereal mash. I believe almost any brewing technique can be modified to brew with a bag.
Since I own a mash tun, I still use it often. It’s great to have a tool kit with many tools.But, I often think that if BIAB were around when I first started brewing, I may never have purchased one.
Hear the Basic Brewing Radio episode where I first learned the details about BIAB.