Imperial IPA SG was way low

[korgman]

I've probably done around 15 AG brews with a 5 gallon mash tun. This week I got a 10 gallon cooler, 17 pounds of grain, and went off to make and imperial IPA. Pro Mash predicted a SG of 1.084.

It came in at 1.052. I'm not sure what I missed. Normally, for 10-12 pounds of grain i will mash with 3.5 gallons of water. For this much bigger beer and doing the math, for 17 lbs of grain, I used 5.5 gals at a 161 strike temp, and my mash settled in at 152. Everything seemed to be going well. After mash and sparge I got almost 7 gallons of wort, and did a 90 minute boil which got it back down to about 5.5 gallons. But the FG was only 1.052.

I'm definitely confused by what i could have done wrong. I've never missed a SG like this. I'm usually within .02 of what ProMash predicts.

 

[bassbone]

There are a few threads talking about low efficiency in higher gravity beers. It is not at all uncommon for people who normally have efficiencies in the 75%-85% range to drop into the 60's.

What is your usual efficiency?

Sounds like this was the first brew in the new cooler.... Is the footprint similar to the 5gallon one you were using? (thinner grain bed could hurt things)

Are you 100% positive the grain crush is exactly the same as your previous batches?

Totally sure about volumes? If you ended up putting more than 5 gallons into the primary, and beersmith's calculations were for 5 gallons, that could also explain some of the difference.

 

[hoppymonkey]

I had the same problem when I upgraded to the 10gallon MT. I compensated by stopping my sparge half way and stirring the grain for a few minutes. My efficency when right back to the usual 75%. Don't forget to vorlauf again when you do it.

 

[korgman]

I'm usually around 75% efficiency when I use my HomeDepot 5gal cooler, this was my first mash using the larger HD 10 gallon. I figured I would just sorta scale everything up accordingly. They crush the grain at the local HB store, and I just assume its the same crush. My volumes were pretty much what i expected, nothing that would account for such a low SG reading.

I didn't really think the sparge would matter too much, I thought that most of the initial runnings had all the sugar. I got around 3 gallons out of the initial runnings and sparged out till I got to just over 6.5 gallons of wort.

 

[0110x011]

I'm usually around 75% efficiency when I use my HomeDepot 5gal cooler, this was my first mash using the larger HD 10 gallon. I figured I would just sorta scale everything up accordingly. They crush the grain at the local HB store, and I just assume its the same crush. My volumes were pretty much what i expected, nothing that would account for such a low SG reading.

I didn't really think the sparge would matter too much, I thought that most of the initial runnings had all the sugar. I got around 3 gallons out of the initial runnings and sparged out till I got to just over 6.5 gallons of wort.

Your sparge makes ALL the difference! You haven't mentioned if you're fly or batch sparging. If batch sparging, your efficiency shouldn't change that much. If fly sparging, when you start using a new mash tun, I always suggest you run off as slowly as possible (generally speaking, the slower you run off, the higher your efficiency will be). This way, over a series of batches, you can find a balance between length of time lautering and extraction efficiency you're comfortable with. Always aim low with a new mash tun!

 

[korgman]

I did a batch sparge. I got about 3 gallons out of the first running, and added about 4 gallons 170 water back into the tun, let it rest for 20 and drained.

 

[jmf143]

I moved up from a 5 gallon Gatorade cooler to a 10 gallon this weekend as well. I used a CPVC manifold and batch sparge, and ended up with 7 gallons of 1.067 wort on 15 lbs of grain - 84% efficiency and right in line with what I get with my 5 gallon.