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Old 04-29-2009, 04:33 AM   #1
Nov 2008
Austin, TX
Posts: 356
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AHS Fin Du Monde Clone

12 lb Belgian Pilsner
1 lb Caravienne
1 lb Crystal 20 L
1 lb Red Wheat
8 oz Clear candi sugar

Mashed for 60 min, starting at 152, dropped to 150 at the end
Batch recirc for about 10 min (it actually ran clear almost right away, but I did it a few extra times just for the hell of it)
Sparge water (batch) at 175 for about 85 min to get a 6.5 gallon boil**
1 oz Perle hops at the beginning of the 60 min boil
1 oz Saaz and 1 tsp Irish moss @ the 45 min mark
Cooled to 75 in 13 minutes
Ended up with exactly 5.25 gallons

Refractometer measured about 15.25 brix or 1.062 SG. Target OG, according to AHS, was 1.085.

** - after the sparge, I drained my MLT and ended up with about a gallon and a half of wort. I definitely put in too much water.


It seemed like everything went pretty well except for the extra sparge water in the MLT. Would this amount have accounted for the .023 discrepancy?

If not, what else could have been the issue? I think all my times and temps were more or less accurate. A bad grain crush by AHS maybe? I am using a 10 gal Rubbermaid for my MTL, which only loses about a degree every 30 min, even with the lid removed. (ambient temp about 90 degrees) I double checked all temps with secondary thermometers.

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Old 04-29-2009, 05:04 AM   #2
Dec 2008
Yankee Hill, CA
Posts: 1,541
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Was the recipe set up for 5.25 gallons? I come up with 1.083 as the target OG for 5.25 gallons. Judging from everything I've read on here, crush is usually the main suspect when you have such a big delta. You could always make it up with a couple pounds of DME, if you're so inclined. But you definitely could have left behind some valuable sugars in the extra sparge water. Also, I'm not sure why you would batch sparge for 85 minutes, I don't know if that would effect your efficiency, but you could cut at least an hour off of your process. Or are you really fly sparging?

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Old 04-29-2009, 05:17 AM   #3
Mosa's Avatar
Mar 2008
Seattle, WA
Posts: 74

this happened to me my first few all grain batches. +1 to checking your grain crush. also, checking pre-boil gravity will help you see poor extraction in your mash, giving you time to correct it before you send the beer to the fermenter.

good luck man!

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Old 04-29-2009, 01:38 PM   #4
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Aug 2006
Whitehouse Station, NJ
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Yeah, question about that 85 minute batch sparge. Are you sure you batch sparged or did you trickle the sparge in slow as the wort slowly trickled out? That would be fly sparging. If you added all the water in at once, you should have stirred it up well, recirculated a minute, then drain right away.
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Old 04-29-2009, 02:03 PM   #5
radtek's Avatar
Dec 2008
Posts: 148

Did you weigh your grains to make sure AHS didn't short you? If it was really humid when they weighed the grains the measure could be off in their favor. It could be the crush as well. I would consider these things first.

I've had inexplicable drops in efficiency before.
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Old 04-29-2009, 02:16 PM   #6
Apr 2009
Lafayette, LA
Posts: 312
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1.) Was your volume to high? Meaning, is your wort watered down? If you took too much sparge from your MLT to Boil kettle, you would have a very low gravity. I STRONGLY RECOMMEND CHECKING PRE-BOIL GRAVITY!

2.) What about the crush? was it too coarse or was there channeling? The thing is that the recipe or target OG from AHS is assuming some brewhouse efficiency. Yours is likely different, so you should arrive at a different gravity if you have the same volumes. The only way to get the exact same gravity is to either know your efficiency and hit it perfectly, or to know your pre-boil gravity and boil off rate, and adjust the pre-boil gravity as needed. My efficiency is never the same, so I rely on the pre-boil gravity for control.

I am a noob myself, but since I started measuring and controlling to pre-boil gravity, there is never a surprise after the boil. I always hit my intended OG because I know my boil-off rate.

If you'd like to do the same, use this formula:

(conc. pre-boil)*(volume pre-boil) = (conc. post-boil)*(volume post boil)

An example would be I want 5 gallons at OG 1.050. So if my boil off rate is 1 gal per hour, and I will boil for 60 minutes, I know my volume pre-boil will need to be 6 gallons (to end up with 5 after boiling). Now here's the important part - Use the formula above to find the pre-boil gravity needed. In this case it would be:

(conc. pre-boil) = (.050)*(5 gallons) / (6 gallons)

That gives .042 pre-boil concentration or 1.042 pre-boil gravity.

After you have that number, all you have to do is measure what you're putting to the boil kettle from the MLT. Just keep sparging and diluting until you hit 1.042 (or whatever pre-boil gravity you need). Once you boil for 60 minutes, you'll nail the OG you expect. Guaranteed or my name isn't Pangea.


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