Brew in a Bag (BIAB) Review and Process

by Karl Updated on August 12, 2021

Brew in a bag (BIAB) is an unstoppable force. What started out as a brewing technique that was scoffed at and criticized has become a legitimate homebrewing movement.

Below, I’ll tell you about my first all-grain brewing experience using the BIAB brewing method and review the bag that I used.

Here’s the gist of it:

  • Everything is done in one vessel. You mash and boil in the same kettle and there is no sparge (at least traditionally).
  • You mash in your pre-boil volume of water, taking into account evaporation and grain loss.
  • When you’re done mashing, you remove the bag, let it drip for a few minutes, then set it aside and bring the wort to a boil.

Pretty simple, eh? That’s the idea.

Here are some things to consider when BIAB bag shopping:

  • Fit: Standard vs Custom
  • Material
  • Weave density
  • Draw strings or velcro to cinch around the kettle
  • Straps for hanging the bag

Fit

You basically have two choices: Standard or custom fit. A standard bag will fit a range of kettles, some better than others. On the other hand, a custom bag is made to your specifications.

The standard bags are certainly cheaper, but the custom fit can satisfy unique needs. For instance, if you want to direct fire your kettle for step mashing, you can get a shorter bag to keep it from coming into contact with the bottom of your kettle.

Keep in mind that a correctly fitting bag saves you money on a false bottom or screen.

Materials

As far as I can tell, most bags are nylon, polyester or plastic. Just like anything else you get what you pay for, thicker more durable fabrics last longer and cost more. The weave also makes a difference as does double stitching.

I like the finer weave bags.  They do better job of filtering out fine materials, especially if you like to double crush or fine crush your grains.

Drawstrings/Velcro

You will need to keep your bag securely in place while mashing. You can do this with clips, good fit, velcro or with draw strings. Straps will also serve the same purpose by fitting over kettle handles.

I personally have not found drawstrings that useful.  I have seen the velcro bags in action and they work very well for securing the bag during your mash.

Straps

The straps are the best option for hanging your bag from a pulley system, ladder or even holding the bag with your arms.  

I don’t recommend using your arms unless you are trying to combine brewing with strength training (P-90X homebrewers edition, anyone?).

To collect all of your wort, you want to let your bag drain for at least 10-15 minutes. Save your back and figure out a way to hang your bag.

The Real Time Saver

The first time your all-grain brewing mashtun cleanup consists of lifting and dumping a bag, you will wonder why you didn’t buy one long ago. I think we can all agree that shoveling grain out of a mashtun is one the worst parts of a brew day.

Nothing makes me happier than saving time and effort when I am brewing. Believe me, it is worth spending $10 to $35 to avoid that step. There are bag makers for almost any brewing equipment, including coolers. Whether you are a traditional all-grain brewer or a BIAB enthusiast, I will fill you in what you need to know.

I beat the crap out of bags. If I am not ripping one of the flimsier bags by snagging my built-in thermometer, I am overloading them and destroying them by draining them for an hour from my pulley system.

After destroying a bag a brew session for a period of time, I moved to higher quality bags. They still received the same punishment, but lasted in spite of my abuse.

My BIAB Batches

The first question that pops up for anyone who wants to try out BIAB is, “Where do I get a bag?”

As you can guess, the bag is important. It’s got to be big enough to handle all of your grain and support its weight when wet. You really don’t want your bag ripping during the mash and having your grains empty into the kettle.

A lot of brewers use paint strainer bags. Those have mixed reviews, but what everyone agrees on is that voile is a great material to use. You can sew them yourself, but that wasn’t a project I was up to.

The bags are a sub$50 investment, which I figured was worth it since with BIAB you’re replacing potentially hundreds of dollars worth of equipment.

Might as well make sure you have a good bag, right? These are even customized for keggle brewers like me by adding a tapered bottom. It makes getting the bag out of the keggle easier.

Most Popular
2pk Extra Large (26" x 22") Reusable Brew in a Bag
$15.99
  • SAVE TIME AND MONEY versus traditional mash tuns when...
  • DURABLE - These bags are made of durable polyester and...
  • EXTRA LARGE - 26" wide and 22" tall to ensure you can...
  • This bag will fit kettles up to 17" in diameter and...
  • TWO PACK: This listing is for (2) Homebrew Mesh Brew in...
Detail Page
11/28/2021 12:09 am GMT

How did the bag do?

Beautifully.

I brewed two beers with it, my Brett beer and winter warmer. The winter warmer had the larger grain bill at 14 lbs. This was no problem for the bag. It’s seriously heavy duty and the handles make lifting it no problem.

Some pictures from that brew day are below.

BIAB Bag in keggle during mashing
Mashing 14 pounds of grain in a keggle
BIAB bag in mash tun with lid
BIAB mashing with the lid on
Holding up the BIAB bag
The bag easily holds 14 pounds of grain

You can see how large the bag actually is. I’m sure I could have handled 20 lbs of grain.

The way it fit around the keggle was very nice. I didn’t ever worry about it slipping into the wort.

This bag is awesome, and if you want to try out BIAB then I highly recommend you try this style of brewing out.

Brew in a Bag (BIAB) using a pulley for all-grain brewing method

Do I recommend brewing in a bag [BIAB]?

So far so good.

Two batches isn’t much, and the Brett beer is still getting funky in the basement, but the winter warmer turned out good. At least there was nothing negative I could point to that was the result of doing a BIAB vs traditional brewing.

It’s commonly said that efficiency suffers but I was able to get 74% with no sparge on the first batch and 76% with a dunk sparge on the second batch.

There are some drawbacks though. Lifting a waterlogged bag out of hot wort ain’t easy and it takes so serious shoulder muscles (which I lack) to hold it there while it drips. If I stayed with this method of all-grain brewing, I would use some sort of rope and pulley system like some BIAB brewers use. If you have a really large grain batch size, managing the bag manually will be a PITA.

Overall I think BIAB is a great thing for people getting into all-grain and even experienced brewers who want to cut down on the amount of equipment they own. Personally I’m happy with my set up and will be sticking with it.

How to Actually Brew in a Bag? The Full Brewing Method Process:

I also recently took The Brew Bag mash tun filter for a test drive.

Did it outperform the false bottom I had been using in my cooler? It sure did.

Here are some awesome things I’ve been able to do with The Brew Bag:

  • Increase mash efficiency by about 5%. The filter is so fine that you can double crush or fine crush the grain, and you can literally squeeze all of the wort out. I’m getting about 78% mash efficiency now.
  • Save about an hour of time. There’s no need to vorlauf since nothing gets through. You can skip the sparge step altogether if you have enough room in the cooler. Also, cleanup is much easier.
  • Reap the benefits of BIAB and then some. OK, not all of the benefits of BIAB brewing method, but definitely some as mentioned above. Plus, coolers are much better than brew kettles at keeping the mash temperature stable at any batch size. Check out my video above to learn more about using bag filters with cooler mash tuns.

If you use a false bottom, braid, or manifold, then I can just about guarantee you won’t regret making the switch to a bag filter like this one. And if you need a cooler, here is the 10 gallon Igloo cooler that I use for all-grain brewing on Amazon.

Should You Trade in Your False Bottom for a Mesh Brew Bag? Yes, yeas you should.

Most Popular
2pk Extra Large (26" x 22") Reusable Brew in a Bag
$15.99
  • SAVE TIME AND MONEY versus traditional mash tuns when...
  • DURABLE - These bags are made of durable polyester and...
  • EXTRA LARGE - 26" wide and 22" tall to ensure you can...
  • This bag will fit kettles up to 17" in diameter and...
  • TWO PACK: This listing is for (2) Homebrew Mesh Brew in...
Detail Page
11/28/2021 12:09 am GMT

Tips for Brewing Big Beers with BIAB

These statements about Brew in a Bag (BIAB) sound familiar?

  • “Are you doing BIAB to learn about all-grain brewing?”
  • “BIAB is a good stepping stone to real brewing”
  • “You can’t get good efficiency BIAB, you can’t brew big beers”
Full Mashtun

I have heard all the misconceptions about BIAB floating around. Most of the ‘information’ came from genuinely well-intentioned brewers, while some of it from patronizing ones.  

Let me assure you that any beer you can make with a three-tiered rig you can also make with your BIAB setup. You can overcome any of the differences with some small process adjustments and a little creativity.

I don’t see BIAB as being limited as much as a different brewing process. Some parts of the process makes for better beer.

Where BIAB Shines with Big Beers

You can sparge with BIAB, but most of us do no-sparge brewing. No-sparge brewing makes for better and more flavorful wort since it is not watered down by sparge water.  Essentially, you are sticking with the absolute best wort your malted grain has to offer.

Traditional English parti-gyle brewing used no sparge brewing for specialty big beers and then made smaller table beers with the second runnings. That is why BIAB is perfect for most big flavorful beers (and makes for a pretty good parti-gyle platform too) .  

For big beers, like a barleywine, no-sparge brewing provides the rich, malty and flavorful wort you want for a beer that can cellar for years.  

I am still drinking the first barleywine I made in 2012 (in fact, I am drinking one as I write this) and it gets better every year. I re-brewed the recipe in January and the batch is currently aging.

Right after you brew it, the hop bitterness smacks you in the face followed by a hefty malt backbone.  As a young beer, it can be unbalanced.  The hops fade over time as malt flavors and aromas morph into something more interesting and unique. After four years of cellaring, the beer has hints of raisin and caramelized sugar with elements of creme brulee and sherry in the aroma.   

I use a lot of dextrin and caramunich malt since the large amount of sugar thins the body.  Here’s the recipe

RobertsBigBarleyWine2012

Robert’s Big Burly BIAB Barley Wine

American Barleywine — BIAB — 1/9/16

  • American Barleywine BJCP Style: 19C All Grain
  • Boil Size: 6.75 gal
  • Boil Time: 60 min
  • OG:  1.108
  • Estimated Efficiency:  75%
  • ABV:  12.7%
  • Yeast:  Saf-ale 05 (2 packets rehydrated)

Malt               

  • 8oz        Rice Hulls
  • 14 pounds     Pale Malt, Maris Otter
  • 1.5 pounds     Caramunich Malt
  • 1 pound     Cara-Pils/Dextrine
  • 4 oz        Caramel/Crystal Malt -120L
  • 2 pounds    Extra Light Dry Extract (3.0 SRM)               
  • 2 pounds     Brown Sugar, Light (8.0 SRM)  

Hops

  • 2 oz of Chinook @First wort hop
  • 2 oz Northern Brewer @ 10-mins
  • Mash at 149F for 90-mins

Fermentation:

  • Pitch at 64F and hold for 48-hours
  • Allow the temp to rise 1 degree F per day holding 70F for 3 weeks
  • Keg or transfer to secondary and don’t think about it again for at least three months.  

Tips for Brewing Big Beers with BIAB

When brewing a high gravity BIAB batch, think about your system and combine the techniques below to hit your target gravity.

First, I will start with ways to maximize your mashtun space. Second, I will give you some strategies for adding fermentables.

To make all of this easier, I would highly recommend buying brewing software, such as BeerSmith. The software is easier and less error prone than using pen and paper or spreadsheets.  

Getting the most out of your mashtun space

Here a few ways to maximize the extract from the space you have:

  • Recirculate
  • Stir your mash vigorously to ensure conversion
  • Do a mashout
  • Boil for 90-mins instead of 60
  • Cold steep all of your kilned malts

Recirculate

This option requires a pump.  If you don’t have one, don’t worry, we have you covered with the next option.

I spend at least 20-mins of my mash recirculating my wort.  When I moved to BIAB, I was concerned about efficiency, so I added a port to the lid of my kettle for closed recirculation.

I was pleasantly surprised after a few brew sessions that my efficiency increased. My mash efficiency is typically over 80%.

Don’t get too hung up on efficiency.  As long as it is a fairly consistent number and you are making good beer, you’ve figured it out.  

This step ensures that the enzymes responsible for converting the starch from your grain to sugar are distributed throughout your grain bed while ensuring starch is more available. I typically heat my mash while re-circulating to avoid temperature loss.  It takes practice to get the heating just right.  

I use this to monitor the temperature at my pump:

TempGauge

In my experience, you can get a good jump in efficiency by adding a recirculation step.  

Stir your mash vigorously

This step has the same effect as recirculating, but without a pump.  Before I bought a pump, I would heat my mashtun while stirring vigorously.  

Again, it takes practice to ensure you don’t overheat your mash or create hot spots, so slower is better. It is always easier to heat your mash than to cool it.

If you want some strategies for troubleshooting your mash temp take a look at this post.

Do a mashout at 165-170 degrees and hold for 10-mins

Heating your mash past 165 will denature the enzymes converting your mash and decrease your wort viscosity.  This allows you to extract more sugars from your grains.  I would recommend recirculating or stirring during this step.    

Boil for 90-mins (or 120) instead of 60

There is no magic here. Your wort concentrates as you boil. The longer you boil, the more concentrated the wort.  

I would recommend using software like BeerSmith or a boil off calculator to determine how long to boil to hit your starting gravity.  

Be careful about boiling too vigorously for too long — you could heavily caramelize your wort. This is great if you are making a wee heavy, but not for other styles.  

Cold steep your kilned malts

This one is pretty self-explanatory.  Cold steep your dark grains (crystal, chocolate, cara malts) and leave your mashtun space for malts that require conversion.  

Depending on your recipe, this could allow for a pound or two of additional malt.

Double crush or fine crush your grainMillingGrain

Lautering your mash with BIAB is a lot easier since you don’t have the same worries about a stuck mash or setting a grain bed thanks to a finely weaved filter bag. Many brewers use this as an opportunity to fine crush or double crush their grain.

Fine crushing means you are setting a smaller gap on your mill. Double crushing means you are running the grain through the mill twice.  

I personally have not seen the advantage of double crushing or fine crushing my grain. As I stated previously, my efficiency never suffered when I moved to BIAB.  

Having said that, brewers that I respect and trust swear by it. This probably brings an efficiency increase of a few points.

Now that you squeezed every little bit of efficiency out of your system, why not just add fermentables?

Add what you need to supplement your grain bill:

Sugar

I have been adding regular table sugar and maple syrup to my beers for a long time. Adding sugar can dry out your beers and thin the body. You can compensate for this by adding dextrin, crystal or flaked malts.  

According to the American Homebrewers Association’s yeast book, yeast produce enzymes early in fermentation to break down maltose (the sugar from malted grain). The presence of too much simple sugar may hinder this production. This can lead to under attenuated beers.  

But when sugar is added a few days into fermentation, it creates a simple sugar party for your yeast when they thought they would have mostly maltose. That’s why I typically add sugar to my fermenter rather than to my kettle.

A good rule of thumb: 1# of sugar adds about 46 points of gravity per gallon or 9.2 points for 5-gallons.  For example, if your wort’s gravity is at 1.080 and you add a pound of sugar, you are now almost to 1.090.  

Tip:  For big beers, if you add sugar to the fermenter, also add yeast nutrient to your sugar addition to reduce yeast stress.

Malt extract

If your setup can only hold enough grain to get to 1.080, then make up for it in the last 15-mins with LME or DME.

You can determine the right amount by using BeerSmith.

A good rule of thumb, 1# of LME adds about 36 points of gravity per gallon or 7.2 points for 5-gallons.  DME adds about 40 points of gravity per gallon or 8 points for 5-gallons.

Tip: Keep the formula above and a few pounds of LME on hand all the time. It is great to have when you undershoot your gravity and want to hit your numbers.

Wrap Up

I have been brewing since college and it wasn’t until reading Gordon Strong’s Brewing Better Beer that I began to value the process of brewing above looking for the one best way to brew.

Spending time perfecting a brewing process with the equipment you have (and re-perfecting it when you get new equipment) brings consistency to your beer.

Create a brewing process that works for what you want out of the hobby, whether it’s small batch brewing, brewing quickly, maximizing repeatability, or just making good beer to share with your friends.

Full Video Transcript:

Hey guys, this is Todd with Homebrewacademy.com and today we’re going to look at using the Brew in a bag technique with a cooler mash tun. Now this is not at all a new concept, but I feel like it’s underrated.

So I want to tell you about my experience with it so far.

If you’re a traditional brew-in-a-bagger, you might be laughing at me already, but if you haven’t thought about using a bag filter in a cooler before, and let’s take a second to look at both sides.

Now I’m in an actual Brew in a Bag set up, you mash in the same vessel that you boil in such as a pot or a kettle obviously. And really the only problem with those kinds of containers is they don’t hold heat very well.

Depending on your setup, you may have to monitor it to some degree, switch the heat source on and off, or wrapping the whole thing in some way to insulate it.

And some people even use the oven to maintain their temperature. So the good thing about the traditional approach is that you only have to worry about one piece of equipment.

You don’t have to worry about transferring any wart and there’s just less to clean up. You can also easily adjust the temperature of the mash if you need to. Like if you missed your mash temperature or if you’re doing a multistep mash.

I personally like mashing in a cooler, you just hit your strike temperature, close the lid and then come back when it’s done. You don’t have to worry about heat loss or adjusting the strike temperature. You just set it and forget it.

Now the traditional approach and using a cooler both have their pros and cons and it really comes down to a matter of personal preference and what helps you in some way, whether it’s consistency in your brewing or just an easier brew day.

When I made the switch to an all-grain, I bought a 10 gallon round cooler, a false bottom and a nice ball valve and that worked perfectly fine. But I wish I had known about these bag filters before dropping all that cash. I’ve found that it’s much easier and faster to use a bag filter like this guy.

This is the Brew Bag. They’re custom made to fit anything that you mash your brew in; pots, keggels, mashed tuns of any shape and size. It’s made out of a very strong and finally woven nylon mesh that doesn’t let any grain bits through.

In fact, you can double crush or find crush your grain to maximize your efficiency and you don’t have to worry about thing. Now when you go on to brewinabag.com you’re going to have to give them the measurements of your mash tun so that they can make a bag that fits just right.

It needs to be loose enough to fill the hole mash ton. On, but snug enough to make it easy to secure it. Some bags have Velcro straps that help tighten the bag around the mash tun, but this bag only has these loops.

So it’s recommended that you use a bungee cord or something similar to make sure that the bag doesn’t slip, which can happen when you’re mashing in and stirring around a lot. I wrote a bungee cord through the handles and each loop on the bag and that seems to work pretty well. You can also have a friend hold the bag in place. Just make sure don’t splash them in the face.

Now if you’re new to the brewinabag concept, this is where you start seeing the benefits of the technique. Once the mash is complete and you’re ready to drain the tongue, you can do one of two things.

You can open up the valve and let the word drain right into the kettle, or you can hang the bag and let all wart drain back into the mash tun. There is no need to vorlauf since there’s no worry of any grain getting through the bag. So that will save you a few minutes right there, especially if you’re sparging multiple times.

So let’s talk about hanging the bag for a minute. In order to get the most out of a bag filter, you’re going to want to hang it. Having the ability to hang the bag prevents flux barges and allows you to get nearly all the liquid from the grain.

There’s all kinds of different ways to hang the bag and it depends on where you brew and the kind of equipment that you’re using.

I brew outside, so I made a pretty simple rig out of an a ladder. Take a 2×4 and eye hook. The top of the ladder has a couple of holes in it, so I’ll just center the 2×4 over the top of the ladder and then I’m marked where the hole was and install the eye hook there.

Then you just attach the pulley hook and now you’ve got a very sturdy and portable pulley rig that costs less than $15 if you’ve already got the ladder. You can buy these pulleys from brew in a bag.com. They’re easy to use. They have a nice locking mechanism and they hold up to 150 pounds, which is plenty.

So once you’ve put all the loops on the hook and you’ve voiced it up the bag, and it usually takes a while for all the work to naturally drain out of the grain. So what you can do is actually squeeze the grain using a thick pair of heat resistant PVC gloves like these. I can get a majority of the liquid out in about five to 10 minutes using this technique. Just be careful not to burn yourself.

So now that all the has been extracted, it’s time for cleanup. Now I’m not going to lie, I hated just about every part of cleaning out the mashed home with my old setup. Half the time the false bottom would fall out when dumping the grain and it was just a pain in the blood trying to get all the green bits out of the filter.

But with the brew bag, you just grab it at the bottom, you turn it over and about 99% of the grain flies right out. Then you just turn the bag inside out, spray it off, hang it to dry, and that’s it.

It doesn’t get much easier than that.

So just to recap, you can use a bag that’s typically used in brew bag setups as a filter for cooler mash tun. It’s a great option if you like the idea of mashing in a cooler and not having to worry about temperature management.

I put this bag through some serious pain and I’ve been really impressed with the quality of the material and now I’m just a huge fan of this process in general. It saves me a lot of time during the mash and cleanup processes. It gives me more time for the good stuff!

Cheers.

Karl S: Lead marketer, brewer, dad, and husband. Pretty much an all-round awesome guy.