Instructions For How To Use The Brew Bag® using the Brew In A Bag (fabric filter) method.

You're about to make great beer!

The Brew Bag® food safe fabric filter allows the mash and boil process to be simplified through the use of one kettle and one burner for the entire process. Compare this to the typical three vessel sparge driven system which includes a hot water kettle, a mash vessel, and a boiling kettle, plus two burners. The Brew Bag® fabric filter serves as the link between the three by combining them into the same vessel.

To summarize the process, The Brew Bag® is placed in the boil kettle after the total volume of water needed to brew has been heated to strike temperature. Grain is then added to the bag (which is in the kettle) and in 45-60 minutes converts the starches into fermentable sugars (the mash). After the mash is complete, The Brew Bag® is lifted out of the kettle to drain, leaving behind the wort (that's brewer lingo for the water + grain results) which is now ready to boil.

To further explain the difference between brew in a bag and a three tier sparge set-up: to reach proper wort volume additional hot water is added to the mash tun after the mash has completed to “push” the wort out of the tun and into the boil kettle. This is called sparging. Depending on the type of sparging this step can take 30 to 90 minutes. The Brew In A Bag method eliminates this step. 

1. General Information.

The Brew Bag® is constructed of food safe polyester materials that will not leach into the wort. All materials have a heat tolerance of 330° - but are not fireproof. The bag is sewn so that it cleans with a shake and a thorough inside and out rinsing. If you use it for pellet hop additions, you will need to hand wash each time with an emulsifying dish soap like Dawn to remove the hop oil residue  .
2. Make sure it fits properly.

Get your brewing kettle, place the bag inside so that the bottom of the bag is flat on the kettle bottom and the top of the bag is outside the kettle. There should be two to four inches overhang on the outside of the kettle and the bag should fit loosely inside all around. It should not pull one way or the other off the sides as you place both your hands opposite each other inside the kettle and press the bag against the sides.

If the bag fits properly, go to step three, if not, please call us right away (815-556-9739) so we can confirm your kettle measurements against the bag you ordered. If we sent you the wrong bag we’ll credit you $5.00 off the bag purchase price and pay overnight delivery of the correct size bag. If you measured wrong, you’ll pay the shipping to return the bag and to receive the correct size.

3. Preparation for use.

Hand wash the bag in very warm water and a mild dish detergent. Triple rinse with clear water to remove all traces of detergent and then hang to dry. The bag will dry very quickly when hung. - THERE IS NO NEED TO TWIST. DO NOT PLACE IN A CLOTHES DRYER.


Basic Brewing Instructions Using The Brew Bag

1. Water Volume 

The Brew In A Bag method calls for the total volume of water to be added to the kettle all at once. To achieve a consistent result, it is necessary to understand and calculate that volume as close as possible. If your calculations are off the gravity reading will be off as well. There are two remedies; add water to the fermenter or boil kettle to lower the gravity, or boil off excess water to increase gravity.

Here’s a general rule of thumb for water volume using The Brew Bag®. An average five gallon batch grain bill (total amount of grain to be used) with pre-boil gravity of 1.035 will call for ten pounds of grain. Each pound of grain will absorb approximately 15 ounces of water. You'll squeeze the bag of grain to regain about 8 ounces, so you'll  toss about 7 ounces with with the spent grain, so it’s a loss of volume.

A five gallon batch calls for 5.25 gallons into the fermenter which equals 672 ounces

Over a sixty-minute boil, based on a number of factors, evaporation will be ten to twenty percent, but you’ll also lose water volume to evaporation heating up and cooling down, so it’s a bit more than that. Trub (proteins and other matter) loss in the kettle, plus in the fermenter will be two to four quarts. So added to the fermenter volume, that’s roughly 7.5 gallons of water. The rule of thumb is: add 8.25 gallons of water to your kettle for an average (OG - 1.035-1.050) five gallon batch. The extra water 3 quarts compared to the chart below is to compensate for the differences in water surface area (which affects evaporation) for all the different kettles used, and trub loss variations, both in the kettle and the fermenter. 

Water absorbed by 10 lbs grain = approx-10 oz per lb Evaporation 7-15% Trub - both in the kettle and the fermenter 5.25 gal into the fermenter Total water needed for 5 gal batch
100 ounces 100 ounces 100 ounces 672 ounces 972 oz = 7.59 gals

If you’re making an above average alcohol content beer, (above 1.050 OG) and use more than ten pounds of grain, add eight oz of water for every pound of grain over ten. That doesn’t sound like much, but eight pounds more (or eighteen pounds total) is sixty-four additional ounces, which is half of a gallon. You can always add water to reach volume and you can always boil longer to reduce volume. 

Total Grain Bill Average 5 gal batch

Average Total Gal Water Total Ounces Total Quarts
8-12 lbs 8.25 1056 33
15 lbs 8.725 1118 34.9
20 9.125 1168 36.5

Water Temperature

Now heat the water to your intended strike temperature (that means the temperature at which you stop heating and add the grain). The temperature of the mash (water with grain added) after adding the grain will fluctuate from batch to batch based on the temperature and volume of the grain. Measure the grain temperature each time and bear that in mind when calculating strike temperature as explained in Rule of Thumb #2 below.



Rule of thumb # 2 - Mash Temperature Calculations

The optimal strike temperature of the water for an average (post-boil gravity of 1.050) beer is approximately 157°. For a ten pound grain bill with a grain temperature of 70° F that is added to 8.25 gallons of water at 157°F (strike temperature) the water/mash temperature will drop 5° to 7° F after adding the grain. That’s why the strike water is a higher temperature than the actual desired mash temperature.

Conversion of starch into fermentable sugars occurs most favorably between 143°F and 152°F, so that’s your mash target temperature range - after adding grain. Sugars converted above 152º are not converted to alcohol by yeast to the same degree as those converted between 143º and 152º

Temp °C

Temp °F Enzyme Breaks Down
40-45 °C 104.0-113.0 °F β-Glucanase β-Glucan
50-54 °C 122.0-129.2 °F Protease Protein
62-67 °C 143.6-152.6 °F β-Amylase Starch
71-72 °C 159.8-161.6 °F α-Amylase Starch

This range is crucial to the enzymatic conversion potential of starches to fermentable sugars. After the grain has been added to the water and stirred thoroughly, record the temperature on your brew sheet instructions. You’ll reference this when recording the temperature loss over the forty-five to sixty minute mash period.

2. Maintaining Temperature

No matter what the ambient temperature, insulating the kettle after adding the grain is important. This is done to maintain the mash temperature in the proper range and keep the enzymes working on the starch to convert it to sugar. 

A good material to insulate the kettle is HVAC duct wrap that has been laid flat, cut to length and then taped with aluminum duct tape. Form a pillow out of the excess to place on the top of the kettle and then drape a blanket over the entire kettle with the insulation in place. Use a bungee cord, or velcro to secure the material to the kettle before putting the blanket on. If you don’t have access to that material, drape a couple of blankets over the kettle - MAKE CERTAIN THE FLAME HAS BEEN TURNED OFF!

If you are brewing on your stove in a three gallon pot or similar, try placing the pot in the oven compartment during the mash to serve as the insulator - do not turn the oven on.

3. Mash Time and Lifting The Brew Bag®

The grain has been added to the kettle, the lid put on, and insulating material applied to the exterior all around. Set a timer for forty-five to sixty minutes (depending of the grain bill size) and have a beer, or mow the lawn, or wash the car, or whatever. This is the prize for using The Brew Bag®, you can brew and complete other tasks at the same time.

The timer alerts you that conversion of starches to sweet wort is likely complete. Unwrap the kettle, lift the lid, and stir the mash thoroughly. Now record the temperature and write it next to the starting temperature reading. You’ll likely record 2° to 4° lower than when you started, and that’s OK as long as the temperature is in the range of 143° to 152°. 

Now lift the bag and let it drain back into the kettle. You can use your hands to lift The Brew Bag® by the loops, but it will get heavy after a few minutes. There is more than one way to lift the bag, so utilize the resources in your brewing space. It’s very simple and cheap to use a 1” x 2” x 24” or so piece of wood placed through the loops to lift The Brew Bag®. Place the wood through the loops, then lay the wood on the edge of the pot and turn it so the bag wraps around the wood and pulls The Brew Bag® out of the pot. This will also squeeze the bag at the same time. Don’t let go of the wood, and make sure to not put undue pressure on one side of the kettle or it may tip over. If you brew in your garage, installing a pulley system or a locking ratcheting pulley in the joists above your brew area is the painless way to lift the bag, and you can also use this to suspend The Brew Bag® in the kettle above the bottom of the kettle for the hop additions.
Let the bag drain until it trickles, or don’t wait, and squeeze the bag (this requires four hands or a pulley system) all around three to four times which will release the wort back into the kettle. Wear brewers gloves, this stuff is hot! Squeezing saves time. After draining, transfer the bag to another pot or your sink, or dispose of the spent grain by grasping The Brew Bag® strapping at the bottom and giving it quick jerk over the trash area. 
To understand this next concept, let’s think about diluting food coloring in a glass of water. The food coloring equates to the sugars derived from the grain during the mash, which, when mixed with water becomes wort. If we add five drops of food coloring to six ounces of water and compare that to five drops in twelve ounces of water, the coloring agent in the twelve ounces is now diluted by twice as much water and the color of the water is half as bold. A gravity reading (OG = Original Gravity) measures the amount of sugar in the wort. If we add or subtract water we change the concentration of those sugars and thus we change the gravity reading.

With that in mind, and after lifting The Brew Bag®, check the pre-boil gravity using a hydrometer or a refractometer and refer to the brew sheet for the target. If you’re within 2-4 points either side, begin the boil. If the OG is more than 5 points on the high side, you may need to add some water, or don't and settle for a stronger alcohol beer. More sugar = more alcohol. If it’s lower than the target by 5 points you may want to boil off the excess. In some cases the cause of the gravity reading being off is a result of the conversion percentage of the starches to sugars - that is generally a result of the mash temperature being too low or too high, so pay attention to those numbers and mash as close to 152° as you can.

By the way, the myth about releasing tannins from the grain by squeezing the grain bag is just that - a myth. Tannins are extracted at mash temps and are a normal result, however, pH above 5.8 combined with temperature above 170º may cause excess tannins to be extracted and that could produce a bitter tasting beer. So, use insulated rubber gloves and squeeze that bag!

4. Emptying The Brew Bag

After the wort has drained, use insulated rubber gloves to empty The Brew Bag® by grasping the bottom of the bag by the strapping and giving it a quick shake. The grain will simply fall out. Shake it a few more times and then turn it inside out and shake again. Then thoroughly rinse in warm water and hang to dry. If you are going to use The Brew Bag® for the hop additions, just rinse and set aside until the boil begins.

A helpful tip.

Ignore the lautering requirement (and this is in BeerSmith software as well) to raise the mash temperature by rinsing the grain with 170° water, or to raise the mash temp to 168° for a “mash-out”. In conventional lautering, this is done to help the wort flow, deactivate the enzymes and stop conversion - listen - you are lifting the grain out of the wort and you have already calculated your water volume and it is in the kettle - mash-out temperature and sparging is not necessary. In addition, you’re going to begin the boil in less than fifteen minutes after lifting The Brew Bag®, so you’ll exceed the 170° mark anyway. In addition, the wort sugars between the bag and the kettle bottom are super-heated and may burn as you stir the grain in the bag while heating. 

5. Boil away - we’re getting closer to the beer!

Boiling the wort does two things - it allows the hops to isomerize (literally change molecularly) which, depending on the length of time in the boil, will impart degrees of bitterness, flavor, or aroma to the beer, so this is a critical step in the process.

If you’re going to use The Brew Bag® for your hop additions, (and we recommend that you do) you must not allow the bag to come into contact with the bottom of the kettle while the flame is on as it may scorch or melt the bag. Find a way to suspend the bag into the kettle about halfway into the wort. That’s additional incentive for using an overhead lift. To keep the The Brew Bag® from billowing during the boil, add some weight to the bag by dropping in something stainless,or copper, maybe a few washers or whatever. The Brew Bag® with the hops inside needs to stay in the wort and not billow.


The second result that occurs from boiling is the reduction of the volume of wort through evaporation. You calculated this loss of volume when you were creating the total volume. At the end of the boil time if the OG result is too low, it is likely because your water volume is too high, so you need to reduce volume by boiling to evaporate and concentrate the wort and hit the OG numbers.

You must consider that the longer the hops are boiling the more bitter the beer will be - so if you need to boil off some water, and you catch the pre-boil OG number as too low, wait until the proper volume is reached through evaporation to add the hops, and then start the timer as required by the recipe.

6. When the boil time is up, lift the bag with the hops, allow it to drain, and proceed as normal to chill your wort into the fermenter.

The first time or two you brew using The Brew Bag®, you’ll discover how to control some of the variables and you’ll change things to be consistently in range of what you’re after. So consider the ambient temperature, actual mash time, the insulating properties of the insulating wrap, and with all that in mind, proceed to the next brew day.