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Old 07-07-2008, 05:11 PM   #1
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Default Hydrometer Accuracy

I have found that in my last 3 batches the OG is consistently .006 below the expected OG. All three batches have been partial mash/extract brews of various types with different OG expectations. Some basic techniques;

I do full boils (start with 5.5 gal) and have not done late extract additions for this reason
Chill with an IC
Top off, usually takes about 3/4 to 1 gal to bring it back to 5.5
Aerate in the primary, then sample with a thief prior to pitching
Test OG with hydrometer in the thief (this seems problematic, as the hydromter has very little room to move around)

But for example:

1.060 expected OG resulted in a 1.054 on my hydrometer
1.054 expected OG resulted in a 1.048 on my hydrometer

FG's for the two hit the expected FG's exactly.

I chilled distilled water to 60 degrees and tested the hydrometer and it measured 1.000. So I'll assume it's good.

As far as the resulting beer, My first batch (first batch ever) was an AHBS Pale Ale and it turned out really good. It fermented well, conditioned well, and had great color and taste. My second brew (honey brown) is in secondary and fermented like mad (I make starters) and I just brewed my 3rd batch (amber) yesterday and it's going crazy in the primary as I type this.

I probably shouldn't worry about it but a consistent .006 variable has me questioning the issue.



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Old 07-07-2008, 05:18 PM   #2
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The first question I'll ask is what your OG before you add the top off water? Also how are you determining your OG's? Are you using brewing software, or are all of your beers kits? I think the gallon of top-off water is what might be throwing everything off.



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Old 07-07-2008, 05:27 PM   #3
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Just curious,

What was the wort temp when you took the OG? IF it wasn't 60F, did you adjust for the temp difference?

The guy I partnered with for my first batch did that. Otherwise, I wouldn't have known.

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Old 07-07-2008, 05:33 PM   #4
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If your hydrometer read 1.000 in 60F water then it's fine. As the previous poster mentioned, you need to adjust your OG based upon the temperature of the wort when you take the reading. You could be correcting your OG by .002-.003. I realize that it doesn't make up all of the difference that you're asking about, but it's a start. The rest could be due to efficiency being a bit low.

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Old 07-07-2008, 05:40 PM   #5
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I didn't measure OG before top off and I've been thinking about that as well. My first batch was an AHBS recipe (not a kit) although I bought all ingredients from them as well. The next two and the examples I used are conversions I did with BeerSmith. In all cases the extract was from a bulk supply (AHBS) and fresh. As for mashing, all temps and times were hit exactly. Of course, that doesn't mean my OG should be perfect but I was hoping for closer to the mark.

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Old 07-07-2008, 05:41 PM   #6
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I did compensate for temperature, which at 75 degrees only allowed for .001.

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Old 07-07-2008, 05:43 PM   #7
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So to bring up the efficiency, would that be a hotter mash or a longer mash, hotter sparge, or ...?

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Old 07-07-2008, 05:45 PM   #8
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I think the recipe's expected OG is based on 5 gallons and you're diluting by 10% up to 5.5 gallons.

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Old 07-07-2008, 05:50 PM   #9
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Quote:
Originally Posted by Bobby_M View Post
I think the recipe's expected OG is based on 5 gallons and you're diluting by 10% up to 5.5 gallons.
Wow. I just did the math...

.060 x 10% = .006
.054 x 10% = .054

I can't believe it could be that simple! Thanks!


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