Different readings on hydrometer vs. Refractometer - Home Brew Forums
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Old 01-08-2012, 03:01 AM   #1
IrishBrewer74
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May 2011
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Ok, so I just got a refractometer for Christmas and admit that I don't really know what I am doing, but it doesn't seem like rocket science.

I made an agave wheat beer tonight. My refractometer read 1.066 but my hydrometer read 1.072. Both readings were from the same sample that I got to a perfect 60 degrees. I had calibrated my hydrometer with tap water also at exactly 60 degrees. I know you are supposed to use distilled, but I have to pick some up. From what I've read tap vs distilled for calibration doesn't make that big of a difference, so any guesses on why the discrepancy? And which reading do I trust?

Any suggestions on a controlled test to determine what one is correct? This was an extract brew, but I hope to start AG within a month and want to be confident with my refractometer.

As always, thanks in advance!



 
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Old 01-08-2012, 03:05 AM   #2
rycov
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the hydrometer should be correct. it seems that the hydrometers need some sort of correction factor for different gravites of wort. (in addition to the calibration against water) i've read that the refractometers don't just read the sugars like the hydrometer does.


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Old 01-08-2012, 03:34 AM   #3
Guess42
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Hydrometer doesn't just read sugar. It reads the density of the liquid, anything dissolved will change the density. Sugar just happens to be the largest component so it is taken as being the sugar.

For the refractometer, did you calibrate it?

 
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Old 01-08-2012, 03:35 AM   #4
Guess42
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As to a controlled test, make up a solution of sugar that is of known concentration an measure with both.

 
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Old 01-08-2012, 03:37 AM   #5
Diver165
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Quote:
Originally Posted by Guess42
Hydrometer doesn't just read sugar. It reads the density of the liquid, anything dissolved will change the density. Sugar just happens to be the largest component so it is taken as being the sugar.

For the refractometer, did you calibrate it?
And not just density, but density for a given temperature. Gotta temp correct your hydrometer readings!

+1 on mixing up some sugar water and checking everything that way
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Old 01-08-2012, 03:46 AM   #6
IrishBrewer74
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Calibrated with water at exactly 60degrees. Wort sample was also exactly 60 degrees. Sample for refractometer was pulled right from the tube with the hydrometer. Shouldn't have been any temp correction needed since it was calibrated at 60, sample was at 60, and hydrometer says to use at 60. Unless i am missing something.

Since I just got it, It prob user error with the hydrometer. But since I want to go AG very soon, I want to get it figured out.

I'm making another extract brew tomorrow and will see what I get then.

 
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Old 01-08-2012, 04:02 AM   #7
Diver165
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No you're right on. Keep us posted. My hydrometer got broke and i was debating getting a refractometer too. I was just pointing out that a lot of people forget to temp correct (including me when I started)
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Old 01-08-2012, 04:28 AM   #8
IrishBrewer74
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I meant user error with the refractometer.

Just ran a test with sugar water and still get a difference between the two. I will recalibrate tomorrow with distilled water. I'm sure it must be something with calibration.

 
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Old 01-08-2012, 04:40 AM   #9
day_trippr
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Quote:
Originally Posted by IrishBrewer74 View Post
I meant user error with the refractometer.

Just ran a test with sugar water and still get a difference between the two. I will recalibrate tomorrow with distilled water. I'm sure it must be something with calibration.
On the refractometer, try using the Brix scale and then converting Brix to SG, and comparing the result to your hydrometer reading. I've often read that some refractometers have inaccurate SG graduations while the Brix scale is correct...

Cheers!

 
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Old 01-08-2012, 10:22 PM   #10
IrishBrewer74
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Did a series of tests today. Calibrated with distilled water as directed. Then took 4 measurements as I increased sugar in the water to see if the discrepancy varied as the SG went up. The first measurement was identical at 1.020. But then after that the refractometer was consistently 4-5 lower than the hydrometer. I got the following hydrometer/refractometer respectively: 40/36, 62/57. 80/76. The fact that the difference stayed consistent makes me think it again is a calibration error but I checked calibration after the tests and it was still zeroed exactly.

The one thing I didn't do was convert the Brix as suggested above (I didn't read that until after I did everything). I'll rerun some tests tomorrow and see what the Brix conversion gets me.



 
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