The Numbers Don't Add Up

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Xiren

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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.
 
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?
 
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
 
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!
 
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!
 
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.
 
If I start my boil and am off by a lot, like 10 points or more, then I obviously missed something important during the mash and I will take steps to correct it during the boil, either by adding some DME or sugar to bump the gravity up, or adding water to dilute. And I will spend time figuring out what went wrong so that it doesn't happen again.

If I'm only off by a few points I just don't care.
 
You're right that the numbers don't add up, but your math is correct, so there has to be something else going on.

Boiling 7.75g of 1.075 down to 6.5g should result in 1.089 (which I think you already know). Either your pre-boil or post-boil volumes or gravity readings must be incorrect assuming you took both readings from the kettle. I know the only way I can accurately measure the volume in the kettle is by weighing it with a scale. Did you mix up the wort sufficiently before taking the pre-boil reading? If not, and you took the sample from the bottom of the kettle, that could easily explain the shortage.

After adding 1.43# DME, I agree your gravity should have been 1.095. The only thing I can think of here is that either the DME was not completely dissolved, or that it was not sufficiently mixed with the wort.

Inadequate mixing would explain everyting, so that's what I am going to guess is most probable.

-a.
 
Did you account for wort contraction during chilling?

What was your final chilled wort volume?
Well, I do not know EXACTLY how much was left in my kettle, but I needed 5.5 gallons in my fermentor and that is what I got.

I checked volume after it was cool, 65*. However, my pre boil volume was checked at about 175*.

Looks like there are a lot of places I could of had my problem.

After adding the DME, I stirred the wort until it was all dissolved. Unless some was on the bottom of the kettle, but nothing was stuck to the bottom during clean up.

Guess, I need to make it again and REALLY take good notes of what I do and when.

Thank you everyone for helping.

:mug: :mug: :mug:
 
Well, I do not know EXACTLY how much was left in my kettle, but I needed 5.5 gallons in my fermentor and that is what I got.

I checked volume after it was cool, 65*. However, my pre boil volume was checked at about 175*.

Looks like there are a lot of places I could of had my problem.

After adding the DME, I stirred the wort until it was all dissolved. Unless some was on the bottom of the kettle, but nothing was stuck to the bottom during clean up.

Guess, I need to make it again and REALLY take good notes of what I do and when.

Thank you everyone for helping.

:mug: :mug: :mug:
All I can say is RAHAHB. Dude 1.090-1.095? The theoretical to the practical is a bridge. Really, how do you know that everything you have is in PERFECT calibration? How do you know the content of the DME? From some table somewhere? I think you did a GREAT job of what you were doing. Congradulate yourself and don't fret over split hairs.:D
 
Well, I do not know EXACTLY how much was left in my kettle, but I needed 5.5 gallons in my fermentor and that is what I got.

I checked volume after it was cool, 65*. However, my pre boil volume was checked at about 175*.

Looks like there are a lot of places I could of had my problem.

After adding the DME, I stirred the wort until it was all dissolved. Unless some was on the bottom of the kettle, but nothing was stuck to the bottom during clean up.

Guess, I need to make it again and REALLY take good notes of what I do and when.

Thank you everyone for helping.

:mug: :mug: :mug:


Yup, it takes a little while to get a feel for what exactly the numbers mean depending on when you take them. You'll get it eventually.
 
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