Brew in a Bag (BIAB) Review and Process

by Karl | Updated: January 2, 2019

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


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.


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.


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.


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.

How did the bag do?


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.

Full Transcript:

Hey guys, this is Todd with 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 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 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!


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