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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Pre Boil Gravity Same as Post Boil Gravity
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Old 08-28-2011, 07:37 PM   #1
mcurtis431
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Default Pre Boil Gravity Same as Post Boil Gravity

I had a pre boil volume of 6.5 gallons and a post boil volume pretty close to 5 gallons. For some reason, both of my gravity readings turned out to be the exact same. I cooled both samples down to the same temperature. I checked by hydrometer and verified that it is calibrated. How is it possible to have no change in gravity readings at two different volumes??? Very confused.


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Old 08-28-2011, 07:52 PM   #2
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I cannot account for that ...some will boil off to a target gravity ...as the volume goes down, the gravity will change.. first I thought temperature, but you say both had same temp, so I am clueless...


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Old 08-28-2011, 08:01 PM   #3
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Its not possible. Either your thermometer or hydrometer are off.
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Old 08-28-2011, 08:10 PM   #4
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Only one reason I can think of, you didn't top it off back to 6.5 gallons did you?
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Old 08-28-2011, 08:23 PM   #5
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Or you took a gravity reading from a sample of your first running if you are doing AG.
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Old 08-29-2011, 12:00 AM   #6
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Could it be possible that the sample I took was not very homogeneous? I took the second sample from the top. Would the wort not be more dense near the bottom?
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Old 08-29-2011, 01:16 AM   #7
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Quote:
Originally Posted by PurpleJeepXJ View Post
Or you took a gravity reading from a sample of your first running if you are doing AG.
This maybe? I have always taken my pre-boil reading from the BK after I sparged to my pre-boil volume. If you think it through, it makes sense. Your first running is going to have a higher gravity than the last running (notice the last running is a substantially lighter color). Other than this, I agree with the others, not possible...
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Old 08-29-2011, 06:02 PM   #8
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I've been in a situation very similar to this before, and found more fastidious practices when taking samples helped some. However, I still very routinely find that I "gain" much less gravity from a boil than I should. So a 1.050 preboil gravity becomes a 1.055 instead of a 1.060 or whatever. I've become *extremely* conscientious about how I take samples--stir, take one, cool, stir, take another, cool, compare--and have recently picked up a refractometer in order to compare readings. I still cannot account for the failure to hit gravity. This thread makes me think that maybe I'm not figuring my boiloff rate correctly, but I also hit volume right on the nose. Any ideas?
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Old 08-29-2011, 06:46 PM   #9
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Quote:
Originally Posted by mcurtis431 View Post
Could it be possible that the sample I took was not very homogeneous? I took the second sample from the top. Would the wort not be more dense near the bottom?
This would be the only thing that makes sense to me. I always make sure I stir it up real good before I pull a sample.


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