BIAB Sparging Techniques

[Homercidal]

Had you measured the before and after squeeze pre-boil volumes, you could have calculated the two different grain absorption rates, and then used the chart in post #9 (https://www.homebrewtalk.com/showpost.php?p=7205802&postcount=9) to determine the efficiency difference due to squeezing.

You are correct that a sparge is likely to give a larger increase in efficiency than a squeeze (also evident by examining the chart in post #9.)

Brew on

Yes, but I didn't squeeze for more than a few seconds, just to see the rate at which it flowed out. I'm not sure I could have accurately measured the difference. I don't think it would have been much.

Honestly, I think a dunk sparge probably extracts more sugars than a full boil, but the difference between a drain and a squeeze is probably much less than that.

Best would be a dunk and a squeeze. If anyone wants to do some experiments, feel free. I'm not interested in caring about the very small difference between them.

 

[doug293cz]

Yes, but I didn't squeeze for more than a few seconds, just to see the rate at which it flowed out. I'm not sure I could have accurately measured the difference. I don't think it would have been much.

Honestly, I think a dunk sparge probably extracts more sugars than a full boil, but the difference between a drain and a squeeze is probably much less than that.

Best would be a dunk and a squeeze. If anyone wants to do some experiments, feel free. I'm not interested in caring about the very small difference between them.

The differences can (and have been, see post #9) calculated with reasonable accuracy. A dunk sparge almost always beats a squeeze, although a really aggressive squeeze can beat a dunk sparge for large grain bills. Squeezing plus sparging cannot be beat (unless you have a filter press.) The efficacy of the squeeze is measured by the apparent grain absorption ratio (gal/lb.) Traditional MLT's have an absorption of about 0.12 gal/lb. A well drained BIAB is in the range of 0.08 - 0.10 gal/lb, and squeezing can get you into the range of 0.04 - 0.07 gal/lb. The lowest I have seen reported is 0.045 gal/lb (by Gavin C.)

Brew on

 

[FatsSchindee]

I do both the dunk sparge and squeeze (both the mash and the sparge, or first and second runnings, if you will). The dunk sparge definitely washes more sugars out, and squeezing it helps. I keep track of volumes, gravities, and absorption rate for every mash, sparge, and then combined pre-boil volumes for all my BIAB brews. I have noticed occasionally that my post-sparge volume will be higher than my pre-sparge volume (i.e., a negative absorption rate), meaning that the sparge effectively washes out some of the wort from the initial mash (that didn't come out from dripping or squeezing), along with all of its own liquid!

 

[doug293cz]

I do both the dunk sparge and squeeze (both the mash and the sparge, or first and second runnings, if you will). The dunk sparge definitely washes more sugars out, and squeezing it helps. I keep track of volumes, gravities, and absorption rate for every mash, sparge, and then combined pre-boil volumes for all my BIAB brews. I have noticed occasionally that my post-sparge volume will be higher than my pre-sparge volume (i.e., a negative absorption rate), meaning that the sparge effectively washes out some of the wort from the initial mash (that didn't come out from dripping or squeezing), along with all of its own liquid!

Interesting about the "negative absorption." The retained wort after the sparge will definitely have a much lower viscosity than the retained wort after the initial runoff. So, I guess it's not at all surprising that more could be squeezed out after the sparge. I have wondered if this could happen, so thanks for the confirmation.

Brew on

 

[FatsSchindee]

Interesting about the "negative absorption." The retained wort after the sparge will definitely have a much lower viscosity than the retained wort after the initial runoff. So, I guess it's not at all surprising that more could be squeezed out after the sparge. I have wondered if this could happen, so thanks for the confirmation.



Brew on

Yeah, it's only happened a couple times, but definitely caught my eye when I was looking at my measurements!

Most of my first running/mash absorption a seem to be around .06-.08 (have seen from .05-.10, though), and, and most of the second runnings/sparge absorptions seem to be .005-.01 (but have seen -.01-.2 or so)...