COVID-19 Update: We Are Fully Operational at This Time and Shipping Daily M-F.

This blog provides information for educational purposes only. Read our complete summary for more info.

March 24, 2022

How to Mash Beer | Brew In A Bag | BIAB

how to mash beer biab

Mashing is simply the process of combining hot water with malted grain to enzymatically break down starches into fermentable sugars. 

Mashing with an electric brew-in-the-bag (BIAB) system has several benefits including:

  1. You can simply set the temp on the controller versus having to wrap a kettle in a blanket and using a cooler
  2. You can also simply turn a switch to activate the pump, as opposed to having to manually collect and pour liquid back into the mash tun.
  3. Less equipment. The BIAB system uses a large mesh basket and a single pot vs 3 pots that a traditional brewing system requires.
  4. When it comes to “mash out,” you can just increase the temperature on the controller instead of boiling another kettle of water and dumping it into the cooler hoping to hit the target.

Here, we will walk through the steps in basic mashing and the different steps involved in what’s called “single-infusion mashing.” But some recipes might call for more advanced mashing techniques, which is something you can read more about in a separate article we have written.

Equipment Needed For Making A Mash

The mash process will go well if you begin with the right equipment, which begins with your mash tun. Some old school homebrew mash tuns are insulated, such as ones made from igloo water coolers; but BIAB systems, such as Clawhammer’s 10 gallon BIAB system, utilize embedded elements and electronic temperature control so they do not require insulation.

Of course, you’ll need the proper amount of grains and water to conduct the mashing process. You may also need to adjust the chemistry of your water before you begin. You can read more about the impact of water chemistry in our article on that topic.

The Mash Process Explained

If using a non temp controlled vessel, the key to a successful “mash-in” is to ensure that mash water reaches the proper temperature after it's mixed with milled grain. To hit the target “rest” or conversion temperature for the particular style being brewed, brewing water will initially need to be heated to a higher temperature than the actual desired mash temperature. This is called “strike temp,” and is necessary because when adding several pounds of room temperature grain to a pot of hot water it will significantly lower the temperature inside the pot. To determine strike temperature, use brewing software such as Brewfather, or just use an online strike water temperature calculator. You might need to check your mash every 15 minutes or so to adjust your temperature.

If using a temp controlled vessel, strike temp doesn’t matter as much. In fact, when we brew beer, we routinely ignore the strike temperature because the controller is able to quickly adjust if needed. Our process is simple, we dial in the desired mash temp on our brewing controller, then add the grain. That’s it. The controller takes care of the rest.

Mash Circulation

Many BIAB brewing systems, including Clawhammer’s, utilizes a pump and hoses to circulate liquid through the grain bed during the mash. Clawhammer’s system actually utilizes a spray valve to ensure that liquid isn’t blasted straight down into the grains, creating a cavity in the middle.

Mash Temperature

Light bodied beers are typically mashed between 145º to 149º degrees F (63-65 C) , while more full-bodied styles are mashed at higher temperatures of about 154-158 degrees F (68-70 C).

If using an insulated vessel without temp control, you will want to check the temperature at different depths inside the mash tun to ensure mash consistency. If using temp control and a pump, the circulation of liquid will keep temperature even.

Note, exceeding 170F will kill enzymes that convert starch to sugar during the mash. If the mash gets too hot, you can cool it by adding ice cubes or cold water. Conversely, you can also increase the temperature by adding boiling water.

How To Test Your Mash For Completion

Once grains have been mashed for 60 to 90 minutes, you can begin to test that the conversion has reached completion. The most basic test you can perform is taste some of the liquid that’s pooled in the grain bed. If it’s become sweet, the mash worked.

This isn’t typically and also isn’t recommended, but you can also perform a more advanced test using iodine, which can alert you to remaining starch waiting to be converted. Start by picking up a small bottle of “tincture of iodine” at your homebrew shop or local pharmacy. Also get a clean white bowl. Then take a sample of the liquid mash, add it to the bowl along with a drop or two of iodine, and watch what happens.

If the iodine turns a color ranging from dark purple to black, give your mash another 15 minutes before repeating the test.  If the iodine remains rust colored, yellow, or light brown, conversion has finished. If the mash process takes more than a couple of hours, you have likely erred in your temperature calculations somewhere along the line or mashed in too hot and denatured the enzymes in the malt.

Performing A Mash Out

Once you have completed your mash, you perform a “mash out,” which involves raising the temperature of the mash to 170 degrees F (77 C) which makes it easier for you to lauter (drain), the remaining “sweet wort” from your tun.

To Sparge or Not to Sparge

Brew in a bag brewing typically does not involve sparging. It can, but it typically doesn’t. Efficiency will be reduced slightly, but most brewing software accounts for this.

If you are using the brew-in-a-bag method and are hell bent on some sort of a sparge, you can also take out your grain bag and place it in a separate container. Then add water heated to 167 degree F (75 C) and let the grains steep for between 1 to 10 minutes. Then lift out the bag and then pour the liquid back in with the rest of your sweet wort. But note, adding  water to the recipe that was not accounted for during recipe creation could actually reduce ABV, not increase it.

If using a traditional mash tun without a basket, you will “sparge” or rinse the grains to collect as much of the converted sugars from them as possible.  The simplest way to tackle this is by pouring two to three batches of water that is heated to the same temperature as your grain bed into the mash tun, stirring it, and then letting it rest before running it out of your spigot. You could also vorlauf or recirculate your wort by draining your wort through your spigot and then pouring back over the mash several times until the wort flows clearly out of the tun.

Once you've completed all the steps to separate your sweet wort from your grains, you’re ready to move on to boiling wort – which is the final step before kicking off your beer’s fermentation cycle.

  • what effect does mash temp have on spirits? if someone mashed the same bill twice. once at 149 and a second at 155, fermented and then ran those threw a still. would there be a difference in the end results? the 155 would have less fermentable sugars, would that make a sweeter spirit?

    Posted by daniel on April 01, 2022

Leave a comment

Please note, the design of our website does not allow us to respond directly to blog comments. Please email us directly regarding questions about products. We don't answer questions about recipes, procedures, etc. However, feel free to leave a comment or respond to comments made by others!

Enter your email address below and we'll send you a free eBook on how to get started with brewing or distilling!