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Old 02-20-2012, 06:15 PM   #1
Feb 2010
SE Michigan, MI
Posts: 86
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I'm going to give BIAB a try but I have a question about water volumes. I've read that most people say to start off with your full volume of water right from the start when you do your mash.

The only thing is, doesn't this give you a very watery mash? I have read that too thin a mash kills efficiency. If you are using a method that tends to have efficiency issues, why not use less water up front then add more after the mash is done?

Just wondering if anyone has an answer to this or if I am not understanding the process.

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Old 02-20-2012, 06:20 PM   #2
Aug 2008
Portland OR
Posts: 5,387
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If you have room for all the grain & liquid then that is the easiest way to BIAB. Some notice an efficiency boost by holding back water for a sparge, but it does make it slightly more complex as you need a separate vessel with sparge water.

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Old 02-20-2012, 06:44 PM   #3
Jan 2011
Toronto, Ontario
Posts: 704
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I recently sewed myself a new bag, and used it for a full volume BIAB, I used to run 80-81% with my sparge step BIAB, I ran 76% with the full volume boil.

So to be honest, I'm not noticing a huge efficiency difference, and the cleanup and time saved make up for the slight drop.

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Old 02-20-2012, 07:19 PM   #4
Feb 2010
SE Michigan, MI
Posts: 86
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I think maybe the thinner mash is supposed to inhibit enzyme activity...maybe that's why they say to do a 90min mash?

How do you do your sparge? Do you the dunk in another pot method or poor water over the grain bag suspended over your kettle?

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Old 02-20-2012, 08:05 PM   #5
tre9er's Avatar
Jan 2012
Lincoln, NE
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They say the enzymes are further spread out so therefore they have harder time converting the starches...not sure if this is the truth or a theory, but it kinda makes sense...

I mash in a cooler with the bag lining it, then pull the bag, dunk in the sparge volume in the BK, let it soak for 10 minutes after stirring, then pour first runnings in afterwards. I've screwed up my water volumes (still figuring my absorption and boiloff rates) twice and I predict I'm in the 75%+ range doing it this way.
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Old 02-20-2012, 08:14 PM   #6
usfmikeb's Avatar
Jan 2011
Leesburg, Virginia
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I'm doing BIAB with less water than is required, and usually run some sparge water through the bag as it's dripping into the kettle. I'll add more water after a small sparge to get to preboil volume on my system. After tweaking my mill settings over several batches, I'm now hitting 75-80% efficiency every time. I setup my recipes based on 75% efficiency, and anything above that just results in higher ABV.

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Old 02-21-2012, 12:28 AM   #7
1MadScientist's Avatar
Apr 2011
Panhandle of Florida, USA
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If you got a big enough pot add all the water needed upfront.

Edit: I was just going to say that I get around 81-82% efficiency with all the water added upfront.
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Old 02-21-2012, 12:44 AM   #8
Nov 2010
Solway, MN
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With the full volume of water in the mash for BIAB the enzymes were so diluted that I only got 80% efficiency.

Oh, you used less water in your conventional tun and got 65%? I guess the enzymes must have been too concentrated.

Think about both of these statements above and tell which is wrong.

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Old 02-21-2012, 03:02 AM   #9
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Mar 2011
St. Petersburg, FL
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Here's a good article with the technical info:

BIAB has the advantage of being able to more finely crush grains, because BIAB has no possibility of a stuck sparge. Finer crush = more conversion at any water volume = ability to adequately do full volume mashes.
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Old 02-21-2012, 05:13 AM   #10
Jul 2010
San Luis Obispo
Posts: 34

Don't know what BIAB means but here is some food for thought on mash thickness. Most breweries will have a mash thickness of 4-5:1. This is because the more concentrated the starch molecules are the more they inhibit the enzymes to work at their maximum speed. However a thicker mash will protect the enzymes in higher temperatures.

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