refractometer readings - Home Brew Forums

 Home Brew Forums > refractometer readings

06-03-2010, 02:33 PM   #1
FenoMeno
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Nov 2009
Grand Haven, Michigan
Posts: 125
Liked 1 Times on 1 Posts

Will the refractometer read correctly after fermentation? I recently purchased one, and used it on my last brew. Instructions were not very clear--

Am I correct that it can be used pre/post boil, but use my hydrometer to check SG during fermentation?

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06-03-2010, 02:41 PM   #2
HairyDogBrewing

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Feb 2008
Mechanicsburg, PA
Posts: 571
Liked 5 Times on 5 Posts

Quote:
 Originally Posted by FenoMeno Will the refractometer read correctly after fermentation?
No, alcohol has a higher refractive index than water and a lower density.

So a finished beer might have a refract reading of about 6 (equivalent to 1.024),
but a hydrometer reading of 1.012.

There are calculators available in Beersmith and online to estimate the FG of a beer based on the OG and the final refract reading.

06-03-2010, 02:49 PM   #3
camiller
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Apr 2007
Omaha, NE
Posts: 1,907
Liked 33 Times on 33 Posts

Simple correction:

Formula for compensation of ethanol effect on refractometer:

SG=1.001843-0.002318474(OB)-0.000007775(OB^2)-0.000000034(OB^3)+0.00574(AB) +0.00003344(AB^2)+0.000000086(AB^3)

SG = Specific Gravity, OB = Original Brix, AB = Actual Brix (Brix Readings During Fermentation)

06-03-2010, 03:17 PM   #4
FenoMeno
Recipes

Nov 2009
Grand Haven, Michigan
Posts: 125
Liked 1 Times on 1 Posts

Thanks,
I have BeerSmith, never noticed the Tab to select what "stage" I am measuring. (defaults to Unfermented Wort Gravity)

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