Help figure out low efficiency...

[Apoxbrew]

I'll just start right off by saying that I know the beer will turn out fine. It'll taste great (I'm sure) and I'll enjoy drinking it. This question is to try and fiugure out where I went wrong in the process more than anything.

So here's the deal. I'm on a 25gal system and have this Imperial Stout recipe I wanted to brew. I couldn't fit the grain bill into the kettle at one time though so I decided to run a split mash. Here was my process in Beersmith on figuring out the split.

Main Recipe Stats:
Grain Bill = 70.75lbs
Pre-Boil Volume = 21gal
Pre-Boil Gravity = 1.088

So for the split mash I started with the original stats above and cut everything in half. Except that Beersmith was telling me that would result in a PBG of over 1.088. So I adjusted down a bit (wasn't a lot) to bring PBG down to the target 1.088. Here's what I ended up with:

Split Mash Stats:
Grain Bill = 33.25lbs
Pre-Boil Volume = 10.5gal
Pre-Boil Gravity = 1.088

All stats were run at 70% efficiency which I hit (or exceed) regularly. During the mash temps were hit fairly close and corrected quickly (my process is to mash in a degree or two low and direct fire up to temp). With the exception that I was mashing twice for one beer, everything was conducted as usual for my brewing process. Unfortunately for both of the split mashes, my pre-boil gravity ended up at only 1.067!!! (58.1% efficiency)

I don't understand what I did... where I went wrong to miss the pre-boil gravity by 20 points!!! Given that my process was the same as with all my brews and that I regularly get 70% or better efficiency and that nothing (that I'm aware of) went wrong with the mash/brew process - I can't figure out where I went wrong.

So fire away with questions and ideas because I'm certainly at a loss here. Again, at 1.081 OG I'm within BJCP range for the beer and I'm sure it'll be quite tasty (it smelled and looked great!). But I certainly would love to know where I went wrong so I can make sure I don't do it again.

Thanks!!

 

[CourtHouseBrewing]

It sounds like this is not your first BBQ.
Let’s say everything went as planned and well with the process, so I would look at the grain bill.
Did you crush it yourself?
Was it a proper crush?
How old was the grain?
How soon after the grain bill was crushed did you brew?
I understand that once the grain is crushed it has a short shelf life.
Hope this helps.
Please let us know what you find.
Thanks.

 

[duboman]

As stated, this is definitely not your first attempt, especially on a 25 gallon set up but this was, I'm assuming a very large grain bill for your system and even though you broke it down well it is possible the sheer size of the bill reduced your efficiency.

When I have done very large grain bills I too have experienced a drop in efficiency because of an inability to get a great mix due to the thickness and weight of the mash in the tun. I have tried to reduce the effect by doughing in slower and having a friend help mix as the grain goes in. I have also tried to mix and stir a few more times during the mash. With these adjustments I was able to get my efficiency back up on subsequent batches.

I will assume you already considered the quality of the crush.............

 

[duckdogs]

How are you sparging batch or fly? My system is set up for 40 gal brew's I found that with the larger grain bills that during the mash we need to mix about every 15 min or so and that batch sparging seemed to give us the best efficency. Using Beersmith batch sparge volumes we initaly run off the add the first water volume mix the mash and recurculate until it clears then run off again adding the next water volume and repeat. My grain mill is set at .038. We have been hitting 90% sence switching to batch sparge from fly sparge. Not sure if this helps but maybe it's a place to start for the next brew.

 

[Apoxbrew]

hehe... ya, i have a few brews under my belt - but certainly am not above making a mistake somewhere along the way or leaning something new with every brew!!

i did crush it myself. i have a monster mill and crush at (or below) 180 RPM at .037
- crush looked good, but to be honest, i didn't check very closely. perhaps i need to pay closer attention from now on to every crush to make sure everything is okay.

i don't know the grain age. i'm at the mercy of the LHBS so it's quite possible it was old. i do store it in air-tight containers but it could have some age on it depending on how long it stat at the shop before i bought it (or how long it sat at the warehouse before it made it to the LHBS).

i crushed friday night and brewed saturday morning. so i don't think that was an issue.

so maybe i got a crappy crush and, potentially some older grain? i'll make sure to check the crush quality every time now. one more step to add to the process for each and every brew i guess!! thanks for the tip!!

 

[Apoxbrew]

wow that was quick... 2 responses while i was typing my reply to the original. thanks gents!

it was a huge grain bill, but split into the double mash, it was actually a small grain bill. so i don't know that that would have impacted anything. certainly had i been able to mash all 70+lbs i would have run into issues but i don't even have the ability to do that in my setup. i think my max is around 48 or 49 lbs at 1.55qt/lb

i fly sparged. so very interesting suggestion. maybe next time i'll try a batch sparge and see? again though, since with the split mash it was really just two normal sized mashes for my system, it's still odd that i'd see such a reduction in efficiency as a result of the sparging process.

i sounds like consensus is building around the poor crush. i'm definitely going to pay closer attention to all of my crushes from now on to make sure they're okay. i guess i got lazy and was assuming my equipment (and ingredients) were behaving on par. thanks for the tips!