Where did all my sugars go???

So yesterday I brewed a 5.5 gal AG Imperial Stout...
18 lbs Pale Ale
.6 lbs Roasted Barley
.6 lbs Choc Malt
.6 lbs Med Crystal
.6 lbs Black Malt
I mashed the whole deal in a 10gal cooler.

This is only my second all-grain brew, so I expected that with that many grains in a 5.5 gal batch I was planning on only about 60% efficiency. If I hit that, I expected to land in the mid-80's with my gravity readings. I was a little lower than that even, and I came in at 56%, and after stirring the wort, I measured 1.062 for 6.8 gallons of wort... so 1.077 equivalent for the 5.5 gallons I wanted.

I was bummed, but I sucked it up and figured "I'm just gonna boost this sucker up a little." After some research on the forums here, I added 1.5 lbs of extra light DME and 1/2C of molasses (~6.2oz), both within the last 15 minutes of the boil. These *should* have added ~16 points to my gravity. After chilling & moving to a carboy, I hit my expected volume right on the screws rockin so I didn't need to top off with any water. Needless to say I was shocked when my gravity reading was only 1.083, as opposed to the 1.093 I was expecting. I was pissed, so I shook the &*%$ out of that carboy for a couple minutes. There was foam all the way to the top of the bung hole. And the new reading... you guessed it... 1.083.

Where the %$#@ is all my sugar going?? The ONLY thing I can think of is that the gravity of the wort is so crazy dense & heavy that I can't possible mix shake the carboy enough to get an accurate & representative sample of its gravity.

A couple more notes on my issues...
1. I've had this problem with other (extract & AG) beers recently. I generally brew big beers (at least 1.075), and the higher gravity ones are further from off from their target OG than the lower ones.
2. I did branch-out recently and brewed a lager. The expected OG was 1.047, and I came in at 1.048. I was super happy/confused.
3. I have purchased and tested a new hydrometer, it works fine. I always adjust for temperature when taking readings.
4. I am considering buying a mix stir.

Is it possible that even after vigorously splashing and shaking the carboy that many of the sugars are still sitting on the bottom of the carboy and that I can't reach them with my siphon? I'm absolutely stumped on how I could possibly be this far off. Even with low efficiency, I compensated for that with adjuncts and apparently not even all of THOSE sugars made it into the carboy.

Frustration.

How much water was in the cooler tun at mash out? How much did you collect? I haven't found temperature compensation to be very accurate. Did you happen to measure gravity before pitching when the temperature is more reasonable? How long was the mash and did you measure temperature at the end of the mash?

First thing to look at is the quality of your crush and it sounds as though that is the start of your problems

Larger grain bills will generally lower efficiency, at least that is my experience due to the difficulty stirring adequately and keeping a good consistent temperature throughout the mash

Sugar doesn't disappear, so you've got 3 options.

Your initial measurements were wrong.
Your final measurements are wrong.
You've lost a lot of wort to trying to strain our hops or trub.

If you brew mostly high OG beers, it would be worth getting an extra calibration point for your hydrometer closer to the range you are interest in. eg known weight of table sugar in known amount of water, bring to a boil, cool and test. Pick density close to what you brew - eg 1.080.

WoodlandBrew said:

How much water was in the cooler tun at mash out? How much did you collect? I haven't found temperature compensation to be very accurate. Did you happen to measure gravity before pitching when the temperature is more reasonable? How long was the mash and did you measure temperature at the end of the mash?

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I didn't record the actual temps of my gravity samples in my documentation for the day, but I remember all of them being in the 105-120d range. Is that too high? All of the specific gravities listed below are corrected for the temp using some brewing software.

* I mashed with 6.5gal water @ 152d for 60 minutes. Temp at the end was 149d. (Initially it was 6gal, but the water was too hot, so I had to add .5 gal of cold water to bring it down.)
* I collected 4.1 gallons of 1.073 in 1st runnings, 2.7 gal @ 1.041. Overall this brough me to 1.062.
* I boiled down to 5.5 gallons, which after cooling brought me to 1.083. That was measured at 72d.

The part that gets me more than anything is the lack of fully recouping the adjuncts. If the 1.062 measurement for the full pre-boil wort was accurate (1.077 for the finished 5.5), then my addition of the DME and molasses *should* have bumped it up at least 15 points to 1.0. My first reaction, like yours probably, was that my hydrometer readings would be rendered inaccurate because of higher temps. But then I've had this same problem a lot recently with my extract beers - coming in 5-10 points below the target OG.

As I see it there are a couple of possibilities...
1) The beers that I brew, generally 1.070+, are dense enough so that it's difficult for me to fully aerate the beer to a point where I am able to get a representative sample for calculating gravity. The heavy stuff stays on the bottom and I can't get to it.
2) I don't aerate well-enough (hard to believe - I usually do a vigorous rock & splash routine for 3-4 minutes).
3) Measuring the gravity at anything over 80d is unreliable, regardless of what brewing software tries to tell me.

In the end I still remind myself that the beer always tastes good. I've never had a problem making great beer. It's just that I'm a big numbers guy and a little type-A, so I occasionally freak out when things like this line-up.

Thanks in advance for your feedback!

duboman said:

First thing to look at is the quality of your crush and it sounds as though that is the start of your problems

Larger grain bills will generally lower efficiency, at least that is my experience due to the difficulty stirring adequately and keeping a good consistent temperature throughout the mash

Click to expand...

I don't think that's my problem... I planned on poor efficiency. The measured gravity of the wort was 1.062 for 6.8 gal, and should have boiled down to 1.077. So I added 1.5 lbs of extra light DME and 6.2oz of molasses to boost it. Unfortunately, even with the adjuncts I still only landed at 1.083. Based on where I was at 6.8 gallons, after adding the adjuncts I should have been closer to 1.093.

So yeah, all of my problems seem to have come after the mash was completely done.

billl said:

Sugar doesn't disappear, so you've got 3 options.

Your initial measurements were wrong.
Your final measurements are wrong.
You've lost a lot of wort to trying to strain our hops or trub.

If you brew mostly high OG beers, it would be worth getting an extra calibration point for your hydrometer closer to the range you are interest in. eg known weight of table sugar in known amount of water, bring to a boil, cool and test. Pick density close to what you brew - eg 1.080.

Click to expand...

I think you're right, but I can't figure out what I'm doing wrong. As I mentioned in another response, the samples of my 1st, 2nd runnings and overall mash collection were done at ~110d. I used brewing software to correct the measurements for every measurement I took. And given that this isn't the first time I've undershot my OG, I started by draining the first 5 gallons from the spigot on the brew kettle, and then strained the hops & funk at the bottom of the kettle into the carboy (I never used to do that). I don't think there was anywhere for the sugar to hide - especially not 0.010 worth of sugar.

However, let's consider that my initial measurements, checking the gravity of the 6.8 gallons from the mash, were incorrect. If everything was wrong based on what I measured from that, that would mean that my efficiency was in the mid-40%s... is that even possible?

Thanks in advance for you feedback!

billl said:

Sugar doesn't disappear, so you've got 3 options.

Your initial measurements were wrong.
Your final measurements are wrong.
You've lost a lot of wort to trying to strain our hops or trub.

If you brew mostly high OG beers, it would be worth getting an extra calibration point for your hydrometer closer to the range you are interest in. eg known weight of table sugar in known amount of water, bring to a boil, cool and test. Pick density close to what you brew - eg 1.080.

Click to expand...

I'll through a couple more options out there:
4) you did not get as much sugar as you could out of the grain
5) Dead space in the MLT left a lot of sugar held up in there.

I think 4 is likely as you said you are boiling from 6.8 down to 5.5. Thats only 1.3 gallons boiloff. Sounds like you are only boiling for an hour?
Most imperials recipes I see look to sparge to a larger volume and then boil for 90-120 minutes to reduce the wort down.
Assumptions only, if you had of collected 8.1G of 1.055 wort (and extra sparge getting ~1.3G of 1.030 wort = total mash eff of 63%) and boiled for 2 hours you would have got 5.5 gallons of aprox. 1.082.

#4 and #5 have nothing to do with sugars for DME or molasses though. Those are fixed numbers and aren't involve in the mash at all.

Next batch, you might just want to cool a sample instead of relying on correction charts. Something is amiss with your measurements, so you might want to start by taking out as many variables as possible. eg temp

I agree with mattd2. The sugar was still in the mash tun. With 20 lbs. of grain, 2.7 gal. sparge water is not enough. Next time you could try double or triple the amount of sparge water. this would definately raise your efficiency. Good luck

Based on you water volumes you should have had 73% efficiency. The mash temperature and time sounds fine, so my bet is on the crush.

I don't trust hydrometers when the temperature is more than 15 degrees from what I calibrated it at. Even with corrections.

4.1/6.5 = 63% first running efficiency
6.5-4.1 = 2.4 gallons grain absorption
2.7/(2.4+2.7) = 52.9% sparge efficiency
63%+27%*52.9%=73% total lautering efficiency

WoodlandBrew said:

Based on you water volumes you should have had 73% efficiency. The mash temperature and time sounds fine, so my bet is on the crush.

I don't trust hydrometers when the temperature is more than 15 degrees from what I calibrated it at. Even with corrections.

4.1/6.5 = 63% first running efficiency
6.5-4.1 = 2.4 gallons grain absorbtion
2.7/(2.4+2.7) = 52.9% sparge efficiency
63%+27%*52.9%=73%

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Huh? Care to explain that in a bit more detail? I agree with the temp corrections, As far as I have seen these are only for small variences over/under the calibrated value.

I've got a blog post detailing it coming up, but in a nut shell, lautering efficiency is all about grain absorbtion. (and dead space if you have that problem)

billl said:

#4 and #5 have nothing to do with sugars for DME or molasses though. Those are fixed numbers and aren't involve in the mash at all.

Next batch, you might just want to cool a sample instead of relying on correction charts. Something is amiss with your measurements, so you might want to start by taking out as many variables as possible. eg temp

Click to expand...

Yeah, agreed. Went back and checked, and calculated if all the DME/mollases got into the fermenter I got a increase of only 12.5 not 16 (but that is still far away from the 6 he actually got).
I see where his question was around the DME/mollases now.

WoodlandBrew said:

I've got a blog post detailing it coming up, but in a nut shell, lautering efficiency is all about grain absorbtion. (and dead space if you have that problem)

Click to expand...

Sweet as, had a look on you blog so that explains why I couldn't find anything

I'll try to respond to several things at once here...

* Thanks for the tip on more water in the mash/sparging process. I knew that was going to be a problem going into it. I had anticipated 65%, but landed with 57%... lower than expected. The problem is that I only have an 8 gallon brew kettle, so 6.8 gallons is pretty much the max I can fit in while boiling. More water wouldn't have helped, although a better quantity balance between the two mashes would have been a good idea.. I suppose I could split the 1st runnings and second runnings into two separate kettles... hmmm.
* my boil-off rate is pretty low (.56 gal/hr) because my stove sucks. I boiled from 6.8 down to 5.5 gal over the course of a 140 min boil. It's about 10d outside right now in MN, but I have a propane burner ready to go come March.
* The efficiency ratings I was quoting are based on a different definition on assumptions, I think. I calculated the potential gravity from the grains mashed (~755 gp) and compared it to how much I was able to extract (~421 gp). There's my 57% eff from my mash.
* In the end, I'm not as concerned about the mash efficiency because I can attribute this to me being a rookie with AG and the fact that I was mashing a huge amount of grain for only a 5.5 gal batch. I think this will improve naturally over time.
* As for the gravity bump I was expecting from the 1.5 lbs of extra light DME and 6.2oz molasses... the sources I have cite the DME to be 44gp/gal (equiv. of 12 gp for a 5.5 gal batch) and molasses (equiv. of 2.5 gp). I guess I was off a little, but still... that should have bumped my 1.077 post-mash gravity up to 1.0915... not just 1.083... right?