Refractometer vs hydrometer post fermentation

CornyKegs 728
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daveooph131

daveooph131

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I recently got a refractometer and took a post fermentation reading as well as with my hydro.

I did the adjustment in beer smith and the refractometer is way off at like 1.002 while the hydro is at 1.013. Tasted the sample and it was great definitely around 1.013 by the taste.

What gives. Those with refractometer do you use it post fermentation or only for pre fermentation.
 
If you want an exact gravity post fermentation use a hydrometer. I use a refractometer most of the time with the conversion factors, but I don't care about the exact gravity.
 
The conversion factors take a measured index of refraction and give you a SG assuming there is only water and sugar. Ethanol has a slightly different refractive index than water, so your measurement won't convert exactly post-fermentation.

(I don't have Beersmith - I use other software - but I assume it's the same.)
 
I don't own a refractometer but I was doing some research and I found that the alcohol in the sample alters the reading. To compensate you need to use a refractometer calculator. It seems to work like the SG to % alcohol calculators.

Now I'm wondering how temperature correction works for refractometers.
 

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