Refracto vs. Hydro difference

[GertSels]

Hi everybody!

I've been having some problems with my refractometer and hydrometer during my last couple of batches.

The situation: I use a refractometer before fermentation (mash, boil, extra check OG,...) and a hydrometer for the OG and FG. I also measure the progress of the fermentation with my refractometer using the Brewfather tool to convert tot SG to check if my fermentation is stable. At the end of fermentation, I measure the FG with a hydrometer just because I feel it's more reliable. However, during my last fermentation (expected FG 1,011), my refractometer indicated 1.010 (After conversion, OG at 1.060 with correction 1,03). My hydrometer indicated 1,016 so it's a pretty big difference. I know my hydrometer is off by 0,002 but still... Any suggestions? I don't know which one to trust.

 

[eric19312]

did you degass your post fermentation hydrometer sample?
CO2 in suspension could give you false high reading. I assume you corrected hydro for temp and were not far from calibration temp.

Also those refractometer correction factors are wort specific aren't they? Was your wort different from the wort you used to come up with the correction factor?

Since you are in group that seems to care about gravity readings I'd suggest getting ahold of a final gravity hydrometer. These are fantastic:
https://www.morebeer.com/products/final-gravity-hydrometer.html

 

[GertSels]

did you degass your post fermentation hydrometer sample?
CO2 in suspension could give you false high reading. I assume you corrected hydro for temp and were not far from calibration temp.

Also those refractometer correction factors are wort specific aren't they? Was your wort different from the wort you used to come up with the correction factor?

Yes. I stirred the sample to degass it and measured when it was at calibration temp. I think the correction factor is instrument specific so I've been using the same number for a couple of batches (based on recommendations from another brewer).