How to Get Started with Brew in a Bag

by Dane Wilson | Last Updated: August 31, 2021

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After having completed multiple extract brews and mastering the process, you might be wondering what comes next. The next big step is all-grain brewing, the most advanced home brewing method. Does that sound a little intimidating or complicated? Yes, even more seasoned home brewers would agree that all-grain brewing can be intensive, which is why there’s a decent halfway point: the brew in a bag or BIAB method.

You can still use the best recipes in your arsenal and save a huge amount of time. Why? Because when you brew in a bag, the mashing, boiling, and cooling is done in a single pot or kettle.

Sound good? Then you’re going to need to know how to brew in a bag, so let’s begin!

What is The Brew in a Bag Method

The brew in a bag method is a lot like using a tea bag to brew a cup of tea. You essentially steep the grains in water to get beer. Of course, the process is a bit more difficult than making a cup of tea.

There’s a technical term brewing in a bag. It’s “all-grain, single-vessel, no-sparge brewing,” and that’s entirely too long. But the term does outline what brewing in a bag is exactly. The “all-grain” part refers to the crushed malts you use instead of extracts. Your single vessel is the pot or kettle that you will be using the entire time. The last bit—no-sparge—means that you can skip washing or lautering your grains.

The BIAB Four Essential Steps

Brew in a bag is a great way to get started with homebrewing or can be used to make your current brewing process even easier. All you need to do is follow the steps outlined for you in this guide.

The four essential steps to the BIAB method:

1. Turn your starches into malt and sugars through mashing
2. Remove the wort, or the liquid, from the leftover grains
3. Add hops then boil everything to achieve your desired level of bitterness and aroma
4. Add yeast to ferment the sugars into beer

Pros and Cons of Brew in a Bag

As you might have already guessed, there are some advantages to the BIAB method, which is why it’s so popular.

What Equipment Do You Need for BIAB?

You don’t need a lot to start brewing in a bag. You’ll need to seek out a few items that you might have yet, but you’ll find most of the equipment list is already in your possession.

You will need:

1. A Brew Bag

This probably comes as no surprise. You can’t brew in a bag if you don’t have the bag. Check out our tips for finding the best brew bag in the next section.

2. Brew Kettle

As mentioned before, brewing in a bag means everything you do—the mashing and the boiling—is going to be done in a single vessel. This means that you’re probably going to have to get yourself a bigger brewing kettle than the one you already have. Remember, you’re going to need enough room to accommodate the pre-boiling part as well as the wort you boil before fermentation.

In other words, to do the BIAB method, you’re going to need a 15-gallon brew kettle to make a 5-gallon batch of beer.

3. Hydrometer and Thermometer

Since you want to hit your target mashing temperature and stay there, it’s important that you have a reliable thermometer. After all, you’re going to need to calculate out the grain absorption rate and strike temperature.

The hydrometer is useful for when you want to measure the original and final gravity of your home-brewed beer.

4. Brewer’s Gloves

You’ll see a little later on why having a pair of brewer’s gloves on hand (pun intended) is a great idea. You’re going to want to purchase a pair that protects both your hands and forearms. Otherwise, you could have boiling hot water trickling down your arms when you go to hoist your brew bag up for draining.

5. Leverage For Lifting The Bag

Many BIAB lovers set up either an A-frame ladder, pulley system, or tripod to let the wort drain completely from the brew bag. Using muscle to hoist the bag is going to be dangerous, so plan out how you’d like to drain the bag first!

6. All-Grain Recipes and Ingredients

Good news! You won’t have to alter many all-grain brewing recipes to be able to brew them in a bag. Simply pick a recipe you would like to try and get to work. It might take some trial and error, but that’s part of the fun.

7. Insulation

While you wouldn’t think about swaddling your brew kettle for extract brewing, you’re going to need to embrace the change. During mashing, temperature control is essential. You can insulate the brew kettle by wrapping a blanket around it. Another option is putting the kettle in the oven or an electric smoker during the rest period.

8. Heat Source

Induction or propane burners or an electric stove are the best ways to heat the brew in a bag kettle. This also means you have greater flexibility when choosing where you want to brew your beer. You can easily set up your BIAB station on a balcony, porch, deck, kitchen, or garage.

You don’t want to use an immersion heater for BIAB, since the coils could burn the bag within the kettle.

Finding The Best Bag For Brew in a Bag

Obviously the bag you use for BIAB is going to be essential to the whole process. Without a quality bag, your beer won’t be the best it can be. Here are some things to consider when you go shopping for a brew bag:

• Fit/Sizing
• Material
• Weave
• Straps and other convenient features
• Velcro cinch vs drawstrings

Let’s have a closer look at these things:

Fit – Custom vs Standard Sizing

There are many options for brew bags out there. One thing to prioritize is the fit. You don’t want to get a bag that is too big for the kettle. If the bag touches the bottom, the bag or the grains inside could get scorched by the heat source.

Standard-sized bags are going to be cheaper than custom-fitted ones, but it might be a good idea to invest in a bag made for your homebrew setup.

A company called The Brew Bag makes bags specially for the BIAB method, as you might have guessed from their name. You can get a standard or customized fit for your kettle. Plus, the bags are durable, reusable, and do an excellent job. You really can’t ask for more.

Materials

Most brew bags made today are either plastic, polyester, or nylon. The more you pay, the thicker and better the material. Look for bags that have double stitching, since that means nothing is going to seep out or escape the bag but all that flavor.

One example of a great brew bag is the Era Natural Mesh Strainer Bag, which is BPA-free and can withstand temperatures up to 248 degrees F (120 degrees C).

Weave Density

Do you plan on double crushing or finely crushing your grains for malt? Then you’re going to need a tightly woven bag. The density of the weave indicates how well grains are going to be filtered out of the malt and wort.

Straps

When you’re brewing a bigger batch of beer, your brew bag is going to end up feeling like a massive kettlebell. This is why straps that connect to a pulley system is a smart design. You can hoist the bag up by the straps to help the bag drain for 10-15 minutes.

Velcro vs Drawstrings

The bag is going to need to be secure during the mashing and brewing process. Many bags come with Velcro, drawstrings, clips, or other convenient features to keep it in place. Some brewers say that Velcro bags are more secure, but you should try both if you’re unsure which one is best for your setup.

The Step By Step How-To For Brew in a Bag

We’ve said it once, but it’s worth repeating: the brew in the bag method is beyond simple. Having gone through the equipment list, you might think otherwise, but just wait until you read how to brew in a bag successfully.

Let’s get started.

1. Preparing Your Brew Grains

The first thing you want to do, before you even begin the brewing process, is clean and sanitize your equipment. Cleaning and sanitizing is one of the most important steps, because even the slightest speck of dirt or bacteria could adversely affect your beer.

Next, since brew in a bag is similar to all-grain brewing, you’re going to need to pre-crush the grains for mixing prior to making the wort.

Crushing your malt grains plays a role in getting the most flavor and starches. Without the starches, you won’t have enough sugar to ferment into alcohol. Wherever you purchase your grains should be able to handle the crushing part for you, but you can always crush your own with a roller mill or even a rolling pin.

2. Making Calculations

Now we get to the fun part (unless you dislike mathematics). You could potentially skip the calculations by using a BIAB calculator. If you need metric measurements for the upcoming formulas, keep the following conversions in mind: 1 pound = 0.45 kg, and 1 gallon = 3.78 L.

Original Gravity and Final Gravity

The first two calculations you make are for original gravity (OG) and final gravity (FG). The former refers to the gravity of the mash prior to fermentation, while your target gravity, or final gravity, is measured once the beer has fermented. You’re going to want to know the OG and desired FG to help with measuring sugar and predicting what qualities you beer will have with the given amount of sugar.

The OG is always going to be a larger number than the FG. This is due to the yeast metabolizing the sugar within the wort. Sugar is dense, but once it has become alcohol, it’s not as dense as the beer’s water content.

Since calculating the OG and FG can be complicated, check out this nifty OG/FG calculator from Homebrew Academy.

Strike Water Amount

BIAB doesn’t use the same 1-2 quarts of water for 1 pound of grain. This means you’re going to use strike water, which is what we call water that is added to the grains for mashing.

You’re going to need to know 3 things to calculate how much strike water you need:

• Weight of the grain. How much grain do you need?
• Absorption rate. How fast does the grain absorb water? Usually, this runs around 0.1 to 0.125 gallons for 1 pound of grain.
• Boil-off rate. How fast does the water boil away? The boil-off rate varies, but you should be easy to track it after a couple of home brews.

Calculating The Pre-Boil Volume

Keeping those variables in mind, you can now start to figure out how much strike water a recipe needs. First, you’re going to need the pre-boil volume, which is calculated using the following formula:

T*B+V=P

• T = the boil time (hours)
• B = the boil-off rate (gallons per hour)
• V = the volume of the batch (gallons)
• P = the pre-boil volume (gallons)

So let’s say you want to brew up 5 gallons of BIAB beer. You know that the grains absorb at a rate of 0.1 gallons per 1 pound of grain, that your boil time is 1 hour, and that you have a boil-off rate of about a 1 gallon per hour.

Plug those numbers into the formula and you get: 1×1+5=6, showing that you need 6 gallons of water to brew 5 gallons of beer.

Calculating Strike Water Amount

Knowing the pre-boil volume means you can begin calculating the strike water volume. The formula is:

A*G+P=Sv

• A = the grain absorption rate (gal/lb)
• G = the total amount of grain (pounds)
• P = the pre-boil volume (gallons)
• Sv = the strike water volume

Put that together and you have: 0.1×12.5+6=7.25. This means that you will need 7.25 gallons of strike water for the 5-gallon home-brewed beer batch.

Calculating Strike Water Temperature

The next thing you need to do is figure out the target mash rest temperature. What that means is the temperature at which the mash will rest before you remove the brew bag, drain it, and then proceed with the boiling.

A general rule of thumb in the homebrew world states that your strike water temperature should be between 8-12 degrees F (4.4-6.6 degrees C) to have your desired mash temperature.

For instance, if you’re 1-hour long mash rest needs 153 degrees F (67.2 degrees C), your strike water temperature should be around 161-165 degrees F (71.6-73.8 degrees C).

You’re going to want to commit to remaining within that target range, because it guarantees that your beer is going to be delicious.

3. Mashing The Grains

Whew! Tired yet? But we’ve only just begun. With all your numbers and gear gathered up, it’s time to make the mash.

1. Add the calculated amount of strike water to the brew kettle.
2. Heat the water to the desired temperature.
3. Put on your brewer’s gloves. Add your brew bag to the water and secure it in place on the kettle.
4. Pour the crushed malting grains into the bag. Stir the contents gently then cover.
5. Grab your thermometer and monitor the temperature. You want to keep the water at the target mash temperature. If the water gets too hot, add some ice cubes. If it’s too cool, add some hot water to the pot. You can also turn on the burner if the temperature continues to fall.
6. Once you have hit the target mash temperature, you can remove the kettle from the heat and wrap it up in insulation. Although it’s recommended that you take the brew kettle away from the heat source for safety, you can keep it where it is. If you do that, be sure to keep the insulation away from the heat, as the material could be flammable.
7. Let the mash rest for the amount of time specified in your recipe.

Don’t succumb to the urge to check on the temperature once you’ve wrapped up the mash and have it resting. You don’t want to disturb the kettle and cause a rapid loss of heat.

4. Draining The Wort

Once your mash is done resting, you need to remove the brew bag from the wort you’ve cooked up. This process is called lautering. Since the water and bag are going to be hot, be sure to wear your brewer’s gloves. Gently remove the bag from the kettle to let the wort drain out. Keep in mind that the contents of the bag and the bag itself are going to be soaked through and incredibly heavy.

Here are some tips for draining the bag completely:

• You can use a sturdy grill rack or large colander to set the brew bag on. Place the rack or colander directly over the opening of the brew kettle or bucket so that the wort can drip back into the container.
• Rig up a pulley system to lift the bag directly out of the pot and hang it.
• Gently—very gently—massage the bag to extract any extra wort. Don’t squeeze it like a stress ball, because that could release bitter tannins.

After the wort drains out completely, empty the grains for your brewing bag into the trash or your composting pile. The bag can be hung to dry. Shake out any remaining grains. With that, your bag is once again ready to use.

5. Boiling The Wort

As the wort drains, you can heat the water for boiling. From this part onward, the process is going to be pretty much the same for whichever form of brewing you choose. Add in the hops according to your recipe. Include finings if you’d like.

6. Cooling and Transferring

Chilling the wort and transferring it to the fermenter is the same as other brewing methods. Want to save even more time? Grab a plate chiller or immersion chiller to get the wort cool fast. If you don’t have such a device, fill the bath with ice and set the brew kettle down there. You want the temperature of the wort to be around 65-75 degrees F before doing anything else.

Transfer your wort carefully to the fermenter. Avoid adding any stray pieces of hops or grains that escaped the bag.

Don’t forget to check the original gravity of the wort during this time. You’re going to need the OG to get the FG and then figure out the alcohol by volume (if you want).

7. Pitching Yeast

Once you’ve calculated the OG, add your yeast to the fermenter. Set your beer aside in a cool area away from daylight for about 7-14 days. The amount of time spent during primary fermentation is based on the kind of beer you’re fermenting. After a week, take another measurement with the hydrometer to see if the beer has hit the target final gravity. When it does, it’s time to bottle your beer.

Ta-da! You’ve successfully gotten through your first round of brew in a bag. From here, you can follow your usual beer-bottling process. Soon, you’ll be able to try your BIAB beer and let everyone know how easy and fun it is to do.

Final Thoughts on BIAB

New and experienced brewers alike can choose the brew in a bag method for added convenience, consistency, and simplicity. Brewing in a bag gives you absolute control over the entire brewing process while eliminating some of the more time-consuming steps, like prepping and sparging. Unlike a three vessel setup, you can make fantastic beer in as little as three hours and with a single kettle.

So are you going to try to make your next homebrew the brew in a bag way?

Brew in a Bag FAQ