Strangely low SG reading part way through fermentation

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guypettigrew
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Re: Strangely low SG reading part way through fermentation

Post by guypettigrew » Sat Dec 19, 2020 3:45 pm

Graham's refractometer calculator seems a bit problematic.

My last brew, before fermentation, showed a Brix of 12.9. The Northern Brewer calculator I use converted this to a gravity of 1.052. My hydrometer, a new one reading to 1.060, showed an SG of just over 1.052. So, the refractometer, with the Northern Brewer calculator, and the hydrometer agreed.

Graham's calculator, with a correction factor of 1.04, gave an SG of 1.050. The 'set calibration' function reduced the correction factor to 1.01 to get an SG of 1.052 from a Brix of 12.9.

OK, so I can use a different correction factor. But then things went really awry.

After 3 days the fermentation had slowed down. The refractometer gave a reading of 7. Northern Brewer converted this to an SG of 12. The hydrometer showed 12 as well. Graham's calculator, on the other hand, showed an SG of 1.022. I don't think the 'set calibration function' is meant to be used for readings during fermentation.

Hope this all makes sense. It feels wrong, somehow, to be negative about Graham's refractometer calculator.

Guy

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IPA
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Re: Strangely low SG reading part way through fermentation

Post by IPA » Sun Dec 20, 2020 8:58 am

I wouldn't be without my refractometer. It is extremely accurate up to the point of adding yeast. So I use it on brew day and after that I use my eyes to monitor fermentation. When I transfer to the secondary FV I take A reading with a hydrometer and again at kegging time.
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