I'm an extract brewer that is going to try a BIAB 5 gallon batch. Reading about BIAB has me wondering why brewers would still do all-grain? Does sparging make that much of a difference?

Also, why do a partial mash and add extract if you have a kettle large enough to steep all the grains?

Ok, last question. Does mashing in the full volume reduce grain efficiency much?


  • Many good answers already so I'll just put an additional thought here as a comment. I have found that many all grain brewers start to scale up to ten gallon batches after they get going. I routinely do 5 gallons but my system lets me go up to 10 whenever I need/want to. BIAB at the 10 gallon level starts to get heavy and you will notice the efficiency difference at that level vs. a sparge method of all grain brewing. Brew in a bag is absolutely a great method for doing less than 5 gallon batches however. My system doesn't work well if I want to test a recipe at 2 gallons.
    – brewchez
    Aug 23, 2016 at 10:50

3 Answers 3


Well BIAB is all grain brewing. Not to be confused with just steeping specialty grains in extract brewing.

If you have a kettle big enough to do a full mash, doing a partial mash and extract is pointless. Unless it's a high gravity beer that would normally need a much larger mash. Basically if you're mashing at all it doesn't save time doing only partial. Though having some fresh grain in will make a better beer in my opinion than all extract, and gives more recipe variety.

Basically a sparge system gives you more control over temp and gives a better rinse of the grains usually giving you better efficiency.

Mashing with a full batch volume of water can give a very thin water to grist ratio and effectively reduce your diastatic power by dilution (less enzymes in actual contact with starches). Also it plays a big role in protein rests making it harder for proteins to rejoin. Usually a range of 0.25-0.35 gallons to 1 lb of grain are typical ratios to play with.


BIAB IS all grain brewing. But it's not traditional multi-vessel brewing. Some batch sparge with a cooler, others fly sparge with a sprinkler, some use a bag for the whole water amount (BIAB). All-grain brewing, each of them.

As for sparging, do note that some BIAB brewers add a sparge step, where they may pour a gallon or so of hot water over the grain bag while it drips over the pot. It does add efficiency points for most who do this. So not all BIAB is sparge-less. Lots of ingenious methods to make wort. Also, large grain bills for high-gravity beers can be unwieldy and might be difficult to manage, or fit as a one-bag brew. In that case, a multi-vessel system can be most beneficial.

As for partial mashes, if you have a recipe that's a partial mash you might not want to spend the time, energy, and money to find the exact all-gain solution. Also, lifting a wet, full grain bill out of the water is heavy and can be messy. A pound or two of steeping or partial mash is much easier to deal with.

Many BIAB brewers find their efficiency in the 80's, higher than traditional methods. Crush it mightily!


I have not had any issues with efficiency with my BIAB setup. But it does takes time to understand how your system works and I squeeze the hell out of my bag. (Without a single issue with astringent flavors.) I use this spreadsheet to help me figure out my volumes. https://docs.google.com/spreadsheets/d/15GRihejTkN0rgrXlFxpBugsVlUSdrZPXQWZmFrnZEhw/edit?usp=drive_web

This big things to figure out are what your grain absorption rate is, and what your boil off rate is from your kettle. This took me a while then bam my numbers were on point.

  • 1
    Yeah, you can't mechanically squeeze out tannins. This may have had a root of truth with bags that could allow husks to exit the bag if disturbed too much (cheese cloth). But with new nylon bags it doesn't happen. Aug 15, 2016 at 4:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.