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Old 01-21-2013, 02:25 PM   #1
emart85
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Default Inconsistent Refractometer Readings

I got a refractometer recently and have been getting some inconsistent readings, I think probably due to my method of taking a sample...

I've been trying to take a well-mixed sample for my pre- and post-boil readings, but seem to get different readings for the "same" sample (+/- 0.005 or worse). I know these things are supposed to be pretty accurate, so I'm guessing there's something I'm doing wrong in my technique. Are there any tricks or good practices for drawing a representative sample that I'm missing?

Also, I seem to have heard that these refractometers are not good for FG readings b/c of the ethanol. Is this true? Is there some sort of adjustment you can make to the refrac reading to get a true FG?

In case you can't tell, I'm not 100% confident in my traditional hydrometer... Any input would be appreciated! Thanks!



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Old 01-22-2013, 12:47 AM   #2
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I know we used to have a problem with having star San/ water / oxy in the "dropper" diluting the wort. Make sure you only put wort on the glass...



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Old 01-22-2013, 12:50 AM   #3
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Quote:
Originally Posted by emart85 View Post

Also, I seem to have heard that these refractometers are not good for FG readings b/c of the ethanol. Is this true? Is there some sort of adjustment you can make to the refrac reading to get a true FG?

In case you can't tell, I'm not 100% confident in my traditional hydrometer... Any input would be appreciated! Thanks!
Yes, once fermentation has started alcohol skews the reading. There are conversions out there, but I"ve never found one that is accurate. Others have found some that work for them.

It can tell you when beer is done, but not the actual FG. For example, if the brix is 6.4 three days in a row, that means the beer is finished. It does NOT mean the FG is 1.025, though! It just means the beer is finished. Then a hydrometer can tell you the actual FG.
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Old 01-22-2013, 02:29 AM   #4
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Make sure you take your readings from a natural light source as well.

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Old 01-22-2013, 02:44 AM   #5
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Calibrate the refractometer with distilled water before each reading. Rinse and wipe the glass surface after each use. Also, take readings in natural light.

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Old 01-22-2013, 03:04 PM   #6
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Thanks for the replies everyone... Should have mentioned that I did calibrate with 68 °F distilled water. May have had starsan in a sample, that could have been a cause. I'll have to take a larger sample so I can "rinse" the pipette with wort first.

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Old 01-24-2013, 03:40 AM   #7
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Do you let the refractometer sit for 30 seconds after you add the sample of it to adjust for the temp?

here is a good article on the subject.
http://www.byo.com/stories/projects-and-equipment/article/indices/29-equipment/1343-refractometers

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Old 01-24-2013, 07:37 PM   #8
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I find this spreadsheet useful.

http://morebeer.com/view_product/6877//Vee_Gee_Deluxe_Refractometer_w__ATC



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