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Home Brew Forums > Home Brewing Beer > General Techniques > The Numbers Don't Add Up
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Old 10-10-2009, 06:51 PM   #1
Xiren
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Default The Numbers Don't Add Up

I made a Holiday Spiced beer today. I should have had a pre-boil size of 7.88 gallons, but only got 7.75. No worries, my pre-boil OG should have been 1.070, but I got 1.075. It was a 90 min boil. After 1 hour 15 min boil, I was down to 6.5 gallons, but my gravity was 1.085. I added 1.43 pounds of DME. At the end of everything, I hit my volume, but my gravity was 1.090, but it should have been 1.095.

Here is my question. If I had more gravity at the beggining of my boil, why was I low at the end? I thought the more you boil off, the more sugars you will have left in solution. That is what I am puzzled about.

Thank you in advance.


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Old 10-10-2009, 07:06 PM   #2
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was your test temp taken into account?


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Old 10-10-2009, 07:08 PM   #3
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You also had less volume at the beginning of the boil. The errors are offsetting.
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Old 10-10-2009, 08:09 PM   #4
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Quote:
Originally Posted by PintOfBitter View Post
was your test temp taken into account?
Yes. I used a refractometer.
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Old 10-10-2009, 08:11 PM   #5
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Quote:
Originally Posted by PintOfBitter View Post
was your test temp taken into account?
I guess I am missing something. I thought if I had a higher pre-boil OG wouldn't the end be high too?
Maybe my problem is "I tought"? =)
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Old 10-10-2009, 08:15 PM   #6
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You had a higher pre-boil OG, but less volume than you expected. Those errors are offsetting. You had more sugar in solution, but less of the total solution. You boiled off less volume than expected, so the increase in SG would not have been as great as if you boiled off more. Does that make sense?
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Old 10-10-2009, 08:19 PM   #7
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None of your numbers add up.

Even the expected preboil gravity vs. the expected final gravity at those volumes.
This equation should hold true, assuming you're not leaving stuff in the BK:

preboil gravity points * preboil volume = final gravity points * final volume


According to my calculations, based on the expected final gravity and a volume of 6.5 gallons, your expected preboil gravity for 7.88 gallons should have been closer to 1.078
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Old 10-11-2009, 12:24 PM   #8
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weirdboy and Yuri Rage, or anyone else for that matter . Let's say you are brewing. It says OG 1.054. Do you hit that DEAD on or are you off a few points? Is 5 points of gravity a BIG thing or what?

Thank you SO much for your help!
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Old 10-11-2009, 12:40 PM   #9
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Would you be feeling better about your brewing if your brewing software had said you should hit 1.090 instead of 1.095?

OG and FG are, in my brewing, just numbers that BeerSmith generates to give me guideposts. I do not think that hitting them exactly equals good brewing and it certainly doesn't equal good beer. There are many other variables (including how accurately or inaccurately I've setup BeerSmith, the precision of my measurements, the list is endless.)

Another way to think about it is that I'm making hand-made beer and do not need the exactitude that AB-Inbev-Miller needs. It's like when I bake bread - I want good, interesting, top quality bread, but I don't need it to come out exactly the same everytime like Wonder or Sara Lee do.

Given this, I generally don't worry about a few hydrometer points either direction of the BeerSmith predictions.

Cheers!

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Old 10-11-2009, 02:24 PM   #10
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I rarely nail the gravity to the exact point. I try to be as precise as possible with the things I can control: grain weight, liquor volume, temperature, etc. I then accept the outcome. If I miss the OG or FG by more than 5 points, I try to find the root cause so I can improve my next beer.


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