Brewing in a bag is the new rage in homebrewing. BIAB, as it is known on the internet, allows for the full range of flavor control of all-grain brewing without the expense of a mash/lauter tun or the need to sparge. The basic idea is that you put a bag in your brew pot, heat your strike water, dough in your grains, mash your grains right there in the pot, then pull the bag out and viola! You’re off to the boil.

Common complaints with the BIAB method are: cloudy wort, thin mash, poor efficiency and lack of mash temperature control. These are all non-issues in my opinion and I’ll explain why.

Cloudy wort does not make cloudy beer at the homebrew scale. If you aren’t familiar with his work, you should be. The Brulosopher is a true beer scientist and performs experiments constantly testing the tribal knowledge of the homebrew community. He has discovered a number of the common “well known facts” about brewing to be totally false!

In one of his Exbeeriments (100% his term, and is probably copywrited) he tested the idea that high amounts of trub will result in hazy beer. He found this to be utterly false and that cloudy wort does not make cloudy beer.

Another great beer scientist, Brukaiser, has done an experiment showing that mash thickness has no effect on the amount of conversion from starch to sugar. So there’s no problem with full volume mashing at all!

Brukaiser (Kai for short) has also shown that there are a number of ways to affect mash efficiency. The duration of the mash and the size of the grain crush are two of the biggest factors. When performing a BIAB brew, it is common to use a finer crush because the risk of a stuck sparge (a clogged filter) is removed, so you could theoretically grind to nearly flower! However, a crush of around 0.030″ is typical for BIAB-ers. You can also boost efficiency with a longer mash time. Many BIAB-er report efficiencies higher than traditional mash-lauter folks.

Finally there’s the issue of temperature control. This is a real issue and there are many ways to fix it. Most BIAB-ers have a jacket (either a literal jacket for humans, or a covering made from some insulating material) that they place around their brew kettle during the mash to retain heat. Or like me, they weren’t smart enough (no offense) to decide on BIAB before spending the money for a mash tun and happen to have one lying around and don’t mind an extra step or two.

I thought I was being brilliant when I thought “why not just mash in a big bag in my cooler? That’ll save me so much time and money.” Then I realized that I was not the first person to think of this and barreled into the internet to learn every BIAB technique out there.

I’ve adopted what’s known as a “hybrid BIAB” setup where I use my mash tun cooler, but still have the convenience of steeping my grain in a bag and easy cleanup. It does add an extra step and a little more work to transfer from my brew pot to the mash tun and back, but it’s not so much that it makes brew day un-fun!


So here we are. BIAB is explained and I thought I’d offer a quick how-to rundown for anyone curious about a step-by-step guide to making beer from scratch. Any experienced brewers who read this, feel free to pitch in and help out or correct my mistakes!

So here is my brewing process for a 5 gallon batch in a nutshell.

  • Heat my strike water (~7 gallons) to ~158F (this temp and volume changes depending on the size of the grain bill, and there’s a ton of online calculators for figuring out your temperature drop due to grain). This is called a full-volume mash.
  • Preheat my mash tun cooler with some hot water and dump it out. Then I fit the bag down into the cooler like a garbage bag. I use binder clips or bungee cords to hold it on the rim of the cooler.
  • Drain in my strike water from the brew pot into the cooler
  • “Dough in” (pour) my grain while slowly stirring inside the bag so that the water and grain mix evenly and there’s no hot or cold spots or lumps.
  • check my temperature and adjust as needed. Mash at 145-152F for light bodied beer and 153-160F for heavy malty beer. I can add hot or cold water at this point to adjust the temp.
  • Put on the cooler lid and have a homebrew! Stir about every 15-20 minutes to break up clumps and maintain even temperature. I mash for 90 minutes to make sure that all the starch in the grains is converted to sugar.

90 minutes later…

  • Drain the wort out of the cooler spout into the brew kettle and squeeze the bag like it owes you money! get every last drop of that sweet sticky wort!


  • Take a hydrometer sample and cool it to room temperature to measure efficiency.
  • Turn on the flame and bring the wort to a boil.
  • Add the hops as per the recipe’s hop schedule.
  • Boil 60-90 minutes depending on the recipe, and put the immersion chiller in for the last 10 minutes of the boil to sterilize it.
  • Chill the wort
  • Hopefully, my lovely assistant (ladyfriend) and resident microbiologist Lexie has already calculated our yeast pitch rate and prepared a starter a day or two in advance. So once the wort is cool to ~65F we drain wort into the fermenter, pitch the yeast and hook up the blow-off hose!

And that’s all there is to it!


A side note about brewing water:

Aside from yeast, learning about water chemistry is the most technical and difficult part about brewing in my opinion, which unfortunately makes a lot of homebrewers overlook it. The mineral content of your water can have a profound effect on your beers’ flavors.

Armed with some basic knowledge of what to look for, I set about to finding a local water report, which is not as easy as it sounds. I finally succeeded with the help of a local brewery, and then I started using a spreadsheet to correct for any deficiencies in the water. It takes time, it takes effort, and hopefully it will yield good results. I highly recommend Bru’n Water as a great place to get all your water information and he has a spectacular spreadsheet that does all the calculations you’ll need!

I typically use 5 gallons of reverse osmosis filtered water and 2 gallons of tap water, along with 1 tsp gypsum and 1 tsp calcium chloride, and ~1/5th of a campden tablet (potassium metabisulfide). I can acidify my mash using either lactic acid (somewhere in the neighborhood of 3 mL, or about 0.7 tsp) or acidulated malt. Proper mash pH is important for enzyme activity, conversion efficiency, and flavor. The ideal mash pH should be between 5.3 and 5.5 as measured by a calibrated high-quality pH meter at room temperature. pH strips don’t work well, so I don’t use them.

Good luck to anyone else attempting to fiddle with their water! and happy beering!