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Old 01-09-2012, 03:52 AM   #521
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Still looking for explanations for my low mash efficiency with BIAB. I did a near full volume mash starting with 7.75 gallons water and an 18 lb grain bill (15.75 lb 2 row and the rest various specialty grains) for a Black IPA. Expected a preboil SG of 1.076 at 75% but got only 1.058 (61%). All my temps were great and held fairly steady. Had my LHBS grind the grain as fine as they could and the crush looked great with a lot of powder (more crushed than in the past). I squeezed the grain bag hard to extract the remaining liquid. I ended up adding a pound of DME during the boil (that's what I had on hand) but still missed my OG by about 0.01. I have had no better than 65% in about 8 BIAB brews. Pretty mystified how folks get 80% or greater and what I am doing wrong. That said, I have been getting very good attenuation so for most I haven't suffered too much ;-) There is nothing wrong with the final product.

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Old 01-09-2012, 04:05 AM   #522
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Still looking for explanations for my low mash efficiency with BIAB. I did a near full volume mash starting with 7.75 gallons water and an 18 lb grain bill (15.75 lb 2 row and the rest various specialty grains) for a Black IPA. Expected a preboil SG of 1.076 at 75% but got only 1.058 (61%). All my temps were great and held fairly steady. Had my LHBS grind the grain as fine as they could and the crush looked great with a lot of powder (more crushed than in the past). I squeezed the grain bag hard to extract the remaining liquid. I ended up adding a pound of DME during the boil (that's what I had on hand) but still missed my OG by about 0.01. I have had no better than 65% in about 8 BIAB brews. Pretty mystified how folks get 80% or greater and what I am doing wrong. That said, I have been getting very good attenuation so for most I haven't suffered too much ;-) There is nothing wrong with the final product.

there could be any number of reasons.. grain crush, water ph... time that you mashed... water volume... amount in kettle pre-boil.. amount in kettle post boil. What I have found is that as the grain bill goes up, efficiency goes down. I feel that this is due to the mass of the grain and not getting getting all the sugars out of the grain. Now had this been a traditional mash you would rinsed those sugars in the sparge. BIAB is a great way to brew, but it does have limitations. When I brew something like a cream ale with a small grain bill, I get 85%.. tonight on an Oatmeal Stout and 11.5lbs I got 75%
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Old 01-09-2012, 04:29 AM   #523
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OK mysticmead, I'll stop complaining I'll keep trying to improve it though. I have tried a batch sparge before and have one time seen a little improvement but I don't think that will every get me to 85%. Then again, probably 7 out of my 10 BIABs have been for beers with greater than 7% ABV so perhaps that is a large part of the problem.

By the way, I enjoy your blog and even posted a comment today on facebook. My first brew of the year as well.

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Old 01-09-2012, 04:32 AM   #524
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A big thanks to all that have contributed to this thread.

I did my first all-grain today with this method (an Irish Red). My OG came out .001 higher than the recipe called for so I'm calling it a success! Now the hard part...waiting!

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Old 01-09-2012, 06:06 AM   #525
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Did my first BIAB this weekend, an American Wheat. For that matter it was my first all grain, heh. It went well for a first time. I was within point of my OG and my efficiency was around 75%.

I did bounce around my marks and made some newbie mistakes but it was fun being a newb again, lol. Looking forward to dialing in a new process and getting it all down to a science.

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Old 01-09-2012, 08:12 AM   #526
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Originally Posted by Brewitt
Still looking for explanations for my low mash efficiency with BIAB. I did a near full volume mash starting with 7.75 gallons water and an 18 lb grain bill (15.75 lb 2 row and the rest various specialty grains) for a Black IPA. Expected a preboil SG of 1.076 at 75% but got only 1.058 (61%). All my temps were great and held fairly steady. Had my LHBS grind the grain as fine as they could and the crush looked great with a lot of powder (more crushed than in the past). I squeezed the grain bag hard to extract the remaining liquid. I ended up adding a pound of DME during the boil (that's what I had on hand) but still missed my OG by about 0.01. I have had no better than 65% in about 8 BIAB brews. Pretty mystified how folks get 80% or greater and what I am doing wrong. That said, I have been getting very good attenuation so for most I haven't suffered too much ;-) There is nothing wrong with the final product.
I feel like a broken record. BIAB taps out at about 1.060. It's a great system for smaller beers but anything over 1060 needs additional DME or boiling off to reach gravities over that number.
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Old 01-09-2012, 11:14 AM   #527
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Still looking for explanations for my low mash efficiency with BIAB. I did a near full volume mash starting with 7.75 gallons water and an 18 lb grain bill (15.75 lb 2 row and the rest various specialty grains) for a Black IPA. Expected a preboil SG of 1.076 at 75% but got only 1.058 (61%). All my temps were great and held fairly steady. Had my LHBS grind the grain as fine as they could and the crush looked great with a lot of powder (more crushed than in the past). I squeezed the grain bag hard to extract the remaining liquid. I ended up adding a pound of DME during the boil (that's what I had on hand) but still missed my OG by about 0.01. I have had no better than 65% in about 8 BIAB brews. Pretty mystified how folks get 80% or greater and what I am doing wrong. That said, I have been getting very good attenuation so for most I haven't suffered too much ;-) There is nothing wrong with the final product.
Efficiency does tend to drop with larger grain bills. More importantly, did you do a mashout?
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Old 01-09-2012, 04:03 PM   #528
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Originally Posted by Brewitt View Post
Still looking for explanations for my low mash efficiency with BIAB. I did a near full volume mash starting with 7.75 gallons water and an 18 lb grain bill (15.75 lb 2 row and the rest various specialty grains) for a Black IPA. Expected a preboil SG of 1.076 at 75% but got only 1.058 (61%). All my temps were great and held fairly steady. Had my LHBS grind the grain as fine as they could and the crush looked great with a lot of powder (more crushed than in the past). I squeezed the grain bag hard to extract the remaining liquid. I ended up adding a pound of DME during the boil (that's what I had on hand) but still missed my OG by about 0.01. I have had no better than 65% in about 8 BIAB brews. Pretty mystified how folks get 80% or greater and what I am doing wrong. That said, I have been getting very good attenuation so for most I haven't suffered too much ;-) There is nothing wrong with the final product.
When I was laid up recouping from a surgery, I had plenty of time to read as many brewing books I could get a hold of. You know, the ones that most of us get and just flip to the section that has the recipes and skip over all the chapters that cover the science side of brewing. I mean, hey are we really interested in calculating the diastatic power of a malt to determine the enzematic potential of the amylase enzymes higher modification and high soluble nitrogen ratio in a Viena Malt vs that of a Bonlander Munic Malt, or are we just trying to understand enough to not screw up our favorite home made beverage?!?

Others have touched on things like PH, Milling, Temps, Time, Mash out, and even Mash Thickness (and yes, a thinner mash does result in higher efficiency than that of a thicker mash, so if you are going with a larger grain bill and not increasing the water volume of your mash to maintain the same gal/lb or Kg/L ratio your efficiency will go down) in this thread, but based on my several weeks of reading, I found this site that is dedicated to the Science of Brewing (from a mostly German perspective, but the info translates well to other forms from a "what's happening" stand point), and in particular this article on "Understanding Efficiency" sums up in a relatively concise manner all of the information that I read from several books and appears to be consistent with what others state both on this thread and in the academic understanding of brewing:

Understanding Efficiency - German brewing and more

So if you really want to know what's causing your efficiency drop, or increase (or just not getting the target you think you should), you can do your homework since it tends not to be based on a single factor approach that most people like to dwell on.

If you understand any or most of what this article covers, you should really send some brew to the Biology/Chemistry teacher you had in your life as a "thank you" (I happened to have an awesome Chem Teacher in High School who actually used the fermenting professions as a way to provide a framework to bring relevance to some pretty deep chem problems he gave us to work out- guessing he was a brewer himself and wanted some help with an issue he was having since this would have been way before homebrewtalk.com came about).

Just looking at the information you included, 7.75 gal of water (regardless of PH) is nowhere near what is needed to get the efficiency you were shooting for. Give the enzymes some more water to work with, something like 1.75-2.5 qt/ lb for a typical thin german inspired mash- if you have the space! Since you would need to start with over 11 gallons of water for the grain bill you described. Don't forget that the grain volume needs to be included as well, which is why I tell BIAB newbies to start with a 15 gal kettle even if they only want to do 5 gal batches and still have the room needed for "big beers". As long as you still "giving a damn" about the other factors you listed (which you will because you brew), you should see your efficiency "improve" (if it doesn't get to what you expect based on an ideal grain to water ratio- which should only get you mid 70's for a %with the ratios above, then one of the other 8 factors is coming into play as well). When I get the insanely high efficiency that others report as well, it's (partially) because I am starting with a mash thickness that is close to a gallon of water/ lb of grain for a session beer like a cream ale (8-9 lb of grain with 8 gal of strike water) so the enzyms have plenty of room and resources to run amuck while you drink a beer in honor of their efforts.

Good luck on your quest for the Efficiency Holy Grail of BIAB on a big grain bill!
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Old 01-09-2012, 04:07 PM   #529
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Since you would need to start with over 11 gallons of water for the grain bill you described.
And you will have to boil to get down to your desired volume and SG, which isn't always good either since "Excessively long boils" (still trying to find out the empirical evidence to back this up, or minimally define how long is "excessive", so any insights are appreciated) or "Excessively strong boils" (at least I found this to be defined as a boil off rate of 15% of volume in an hour) is detrimental to quality. So now you know why the Pros aren't hellbent on achieving the same high efficiencies that us small batch brewers shoot for since there are other consequences in the process they would have to deal with at that scale.

Keeping with a 1 hour boil (since that seems to be the norm, I would guess nobody would call it excessive) and honoring the not greater than 15% boil off in that hour, for my particular BIAB set up with losses to kettle dead space below the valve and plate chiller loss and a goal of 6.5 gal into the fermentor so I can dump trub from the conical, harvest yeast, factor in the loss to absorption by the hops that goes in for dry hopping and still end up with 5 gal of beer in the keg, the post boil volume should be ~7.65 gal, which means a pre-boil volume of 9 gal. When you factor in the gain absorption typical for BIAB (Which is much lower than traditional AG, I seem to recall a consensus of around 1/3 qt/ lb of grain) on your 18lb grain bill it will soak up 1.5 gal of water that you will never get back no matter how much you squeeze. Which gets you to a starting strike volume of 10.5 gal (if you were using my equipment) which is within the range of 1.75-2.5 qt/ lb that the german style brewing shoots for, but still on the higher end - which is desirable when efficiency is a stated goal.

Head spinning yet?!? (you better go grab a brew)

If you really want to go with the 11 gal to start with yet keep your boil off to the cap of 15% per hour, you would have to boil for an extra 15-20 minutes (if the math in my head is in the ballpark- but that's why you put a sight glass on your kettle so you just go til you hit your mark). Is that "excessively long" and potentially detrimental- don't know since I haven't found a definition for excessively long, or what happens when you push it too long...

Give it a try (I can't since I don't have a big enough pot- yet) and let us know if we all need to run out and buy bigger pots, or if we are just stuck augmenting with extract once we play with >15 lb grain bills in a typical 44 qt pot and are stuck with sub 70% efficiency for "big BIAB beers" because we have a bunch of pissed off enzymes that don't have enough water to do their work.


(disclaimer- math done in head while at work doing other things as well, so if I made a mistake point it out so we can prevent someone from suffering from my error, but no need to be a jerk about it- this is why you use brewing software to figure this stuff out)
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Old 01-09-2012, 05:20 PM   #530
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I feel like a broken record. BIAB taps out at about 1.060. It's a great system for smaller beers but anything over 1060 needs additional DME or boiling off to reach gravities over that number.
I'm not an efficiency chaser by any means but my last brew was a 1.066 6 gallon BIAB that I wound up with 1.069 on. I didn't do anything special other than a double crush which I don't usually do. It was more of a screw up with the mill on the first pass that required a second crush.

I'd tell you that if you had a 1,000 gallon kettle and a strong enough bag, mixer and crane you could probably do a massively large BIAB and get good efficiency. I don't see the logic in defining 1.060 as a cutoff point for BIAB.
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