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Old 08-26-2012, 07:12 PM   #1
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Default Calibrate those hydrometers, people

Get one cup of distilled water, cool it to 60° F (or whatever your hydrometer says it's calibrated for), and then test your hydrometer. They usually only cost around five bucks at the homebrew store, so chances are pretty good the quality control on them is not the best. Here's mine. As you can see, it should be reading 1.000 but it's reading 1.004, so it's .004 points high, so all of the wort / beer I test with this thing has to have .004 points subtracted from the readings.

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Old 08-26-2012, 07:25 PM   #2
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Looking at that, I see 1.000. I believe you read these from the top of the meniscus.

Good idea to make a sugar solution and do a 2-point calibration. I have 3 hydrometers and tested them @ 1.000 and 1.100. 2 of them were nearly perfect at both ends. The other read 1.002 with water and 1.111 with the 1.100 solution!

Thats an error of 11 points at high gravity. Wow.

I tested against a refractometer.

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Old 08-26-2012, 07:59 PM   #3
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That looks like 1.000 to me too...

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Old 08-26-2012, 08:05 PM   #4
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Read from the bottom of the meniscus

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Old 08-26-2012, 08:06 PM   #5
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The calibration is only as accurate as your thermometer (and ability to read the instrumentation properly).

ABV and attenuation will not change so long as your hydrometer reads linearly, and the samples were taken at proper temp. You may be fooled into thinking that your efficiency is consistently low or high, but let your palate be the ultimate judge, not some lab instrument.

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Old 08-26-2012, 08:12 PM   #6
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Quote:
Originally Posted by silvery37 View Post
Read from the bottom of the meniscus
Agreed. At least that's what I was taught by my Chemistry professor.
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Old 08-26-2012, 08:13 PM   #7
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Quote:
Originally Posted by Yuri_Rage View Post
The calibration is only as accurate as your thermometer (and ability to read the instrumentation properly).

ABV and attenuation will not change so long as your hydrometer reads linearly, and the samples were taken at proper temp. You may be fooled into thinking that your efficiency is consistently low or high, but let your palate be the ultimate judge, not some lab instrument.
A few degrees error on a thermometer don't make 1 gravity point of difference. So, while temp does effect the reading, the accuracy of the thermometer is not very important.


As I demonstrated above, the error in one of my hydrometers was not just an offset. This error would have resulted in incorrect ABV and attenuation. I agree we are in the minutia of brewing process, but hell that's what we do here, right?
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Old 08-26-2012, 08:17 PM   #8
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Quote:
Originally Posted by DarthMalt View Post
Agreed. Looks like 1.004.
Ray Daniels, on page 14 of Designing Great Beers, says this (I've got it opened in front of me here):

"Also, read the hydrometer correctly. (The hydrometer reading should be obvserved at the top of the small meniscus thet forms around the hydrometer shaft). While this might seem simple, I did it incorrectly for nrearly six years!" [emphasis is Ray's, not mine]
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Old 08-26-2012, 08:18 PM   #9
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Now I'm all confused! I think I always read the top, too. Dammit, I can't even remember. More Google!

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Old 08-26-2012, 08:18 PM   #10
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Quote:
Originally Posted by passedpawn View Post
Ray Daniels, on page 14 of Designing Great Beers, says this (I've got it opened in front of me here):

"Also, read the hydrometer correctly. (The hydrometer reading should be obvserved at the top of the small meniscus thet forms around the hydrometer shaft). While this might seem simple, I did it incorrectly for nrearly six years!" [emphasis is Ray's, not mine]
I'll trust a science textbook. Thanks.

Unless, for some reason, beer hydrometers are calibrated differently... I'm not sure of this though.
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