BIAZB: Brew in a Ziplock Bag

Johannes Fahrenkrug
Home Brewing
Published in
5 min readMar 24, 2021

Brew your beer like you cook your steak.

I was interviewed about this technique by James Spencer on Basic Brewing Radio in this episode:

I usually brew 2.5 gallon batches, but I recently rediscovered the joy and simplicity of brewing small 1 gallon batches. I own an Anova Sous Vide stick that I’ve used for brewing in the past, but I never really liked it: The sous vide stick should only really be in contact with water, not with sweet wort. Also, when separating the sous vide stick from the mash using a hop spider or something similar exposed another flaw: the mash temperature was uneven, because the stick only really recirculated “in place”, but didn’t evenly heat the mash. What to do?

It turns out you can sous vide your mash, just like you can sous vide a steak: in a ziplock bag!


  • Use filtered water (or whatever brewing water you want to use) and put enough of it in a pot so the water goes at least above the “min” line on the sous vide stick. This is usually a little more than your mash and sparge water combined.
  • Using the sous vide stick, heat the water bath to the desired strike water temperature.
  • Put your crushed grains in a 1 gallon or 2.5 gallon ziplock bag. Don’t cut corners on the bags, get the good ones.
  • Once the water has reached the strike temperature, turn off the sous vide stick so the water can cool down to mash temps while you dough in.
  • Using a 1.25 quarts of water per 1 pound of grain ratio, add strike water from the pot to the ziplock bag and mix everything thoroughly with a whisk or spoon (just make sure it’s not something with sharp edges that would damage the bag). Also be careful not to get any grain particles in the “zip.” Seal the bag.
  • Put the bag in the water bath. I like to clip it to the edge of the pot. Set the sous vide stick to your mash temperature and turn it on.
  • After about an hour, increase the temp to 170º F for mashout.
  • Using BBQ gloves or something similar, take out the bag and place it on a colander or a strainer. Carefully open it: The hot grains are very eager to get out of the bag, especially when using a 1 gallon bag. It’s much easier when using a 2.5 gallon bag. Sparge using the appropriate amount of water from the pot’s water bath. It serves a dual purpose: Water bath for the mash and sparge water!
  • Boil etc as usual.


I’ve made several tasty beers using this technique and I really enjoy it. Here’s a random list of things that might be an advantage of this technique.

  • Easy temp control during the mash.
  • Low equipment cost.
  • No extra vessel for the sparge water needed because both mash water and sparge water heat up at the same time.
  • Possibly clearer wort as compared to BIAB because you can sparge.
  • Possibility of mashing grains for two different beers at the same time in the same pot.
  • Cleanup is a breeze.
  • Easy to do a step mash.
  • Easy to do a sour mash: You could just lower the water bath temp to 113/120º F after the mash, keep the mash in the ziplock bag, inoculate with uncrushed grains, and let it sour in the same ziplock bag for a few days. Since it’s not exposed to oxygen you shouldn’t get any dumpster flavors etc.
  • Might be interesting for LODO brewers.
  • Possibility to do a thick mash with the simplicity of BIAB: Simply put your BIAB bag in the kettle, follow the process described above with the ziplock bag and the water bath, and then dump the contents of the ziplock bag into the water bath after the mash. Lift out the BIAB bag as you would after a normal BIAB mash. Just make sure you adjust the amount of water in the kettle to match your sparge water before you empty the contents of the ziplock bag into it.


Of course this process isn’t perfect. Here are a few challenges:

  • Gravity limit because of bag size. In a 1 gallon ziplock bag the maximum is about 2.6 pounds when using 1.25 quarts of water per pound of grain.
  • Can’t stir mash in 1 gallon bag. Not a problem when using 2.5 gallon bags.
  • I love the smell of grains during the mash. With the ziplock bag you don’t get to smell the mash. For some that might actually be an advantage.
  • Difficult to handle 1 gallon bags: They can be hard to close, especially if little grain particles get in the “zip”. Again: Use 2.5 gallon bags if you can. Much easier to handle.


I enjoy this process and I want to experiment with it some more. One thing I’d like to try soon is an overnight mash: Not using a sous vide stick at all, I’d like to put the strike water in the ziplock bag the night before and just let it sit (preferably in an insulated cooler or something) and the sparge and brew the next morning. The length of the mash will probably make up for any loss of temperature.

So there you have it: BIAZB — Brew in a Ziplock Bag. Not the greatest thing since sliced bread, but maybe another tool in the toolbox.