Refractometer question

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ayoungrad

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A couple things:

The refractometers that have SG scales (at least all the ones I'm aware of) aren't correct. The manufacturer(s?) used the "multiply by four" rule instead of actually putting in a conversion.

They're calibrated for sucrose solutions, but wort is primarily maltose. Typically you convert by dividing by 1.04 - so a reading of 20°Bx means the SG is actually about 19.2°Bx (1.079).

After fermentation starts, the alcohol in solution will result in an artificially high SG reading. You can try to compensate using an empirical correlation. There are two that I know of: one is included in ProMash, BeerSmith, the MoreBeer spreadsheet, etc. I recently developed the other. Everyone I know of who's tried both has found the standard correlation to be less accurate.

http://seanterrill.com/2011/04/07/refractometer-fg-results/
Awesome. Thanks for the link. I'll definitely be incorporating that into my spreadsheet.
 

HairyDogBrewing

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One Brix is 4 gravity points - for sucrose.
The refractometer is off a little bit for wort, so there is a small correction factor.
So if you take OG with both hydro and refract you'll see what correction is needed and put that number in BeerSmith's refractometer tool.

I think Yooper helped to develop this, so maybe she can explain it better than I can.
Follow up:
In BeerSmith it's called "Wort Calibration Value".
For instance, if the refract reads 15.0 Brix and the hydro reads 1.059 (after temperature correction); then the WCV would be 1.04.
 

a10t2

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Octavius

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Sean,
Thanks for the link re: the wort correction factor.
Cheers!
 
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