Refractometer consistency

[Tal Orbach]

Weird thing,
I had a batch of wort which I started fermenting in 2 different vessels (in the same fridge - so conditions where effectively the same).
After a few days, one of them gave me a refractometer reading of 5.5 Brix, and the other was 6.1 (took several readings of both - these numbers remained consistent throughout the readings).
However, When I took a hydrometer reading, both presented a gravity of 1.013.
So, the gravity is the same, but the Brix reading is different. The only explanation I could think of for this is different ABV or something, but why would that be the case, if they fermented in similar conditions? (one of the containers was open, but it was at 18C, so I don't think there was a lot of alcohol evaporation going on)

Any thoughts?

 

[White Haus Brews]

Hmm how strange. I wouldn't think alcohol evaporation would be the case since that would show up with the hydrometer as well. I'm assuming yes but they were both tested at the same temperature, right? Did one fermenter get more kettle trub? Or dry hopped differently? I wouldn't think either of those would matter too much but just thinking out loud. What was the OG Brix by chance?

 

[Tal Orbach]

I'm assuming yes but they were both tested at the same temperature, right?

Yeah

Did one fermenter get more kettle trub?

I don't think so.

Or dry hopped differently?

No dry hopping at all (or anything of that sort)

What was the OG Brix by chance?

I didn't take a Brix reading prior to fermentation, but the hydrometer showed 1.050

 

[White Haus Brews]

If you go with that OG your brix was around 12.5 which based on the refractometer calculator your corrected FG on each fermenter was 1.005 and 1.009 which are obviously not only different than each other but way considerably off your hydro.

Seems like somethings up with your refractometer. Have you tested them side by side in the past? Less likely the hydrometer since at least that's consistent but have you made sure it sits at (or at least near) 1.000 in water?

 

[Tal Orbach]

If you go with that OG your brix was around 12.5 which based on the refractometer calculator your corrected FG on each fermenter was 1.005 and 1.009 which are obviously not only different than each other but way considerably off your hydro.

From what I've read, every refractometer has some correction factor, which needs to be calculated, no?
Anyway, I haven't really figured out mine yet, but I guess with the correction factor, one of these readings could work to match the hydro.

Seems like somethings up with your refractometer. Have you tested them side by side in the past? Less likely the hydrometer since at least that's consistent but have you made sure it sits at (or at least near) 1.000 in water?

I check the refractometer with water every time I use it. It's always on 0. Never needed any calibration...

 

[White Haus Brews]

Yeah fair enough. Yes every refractometer has it's own correction factor and it might help a little but seeing 2 different results from the same gravity wort isn't confidence inspiring

 

[Tal Orbach]

I agree. That was exactly my problem.
The problem is that while it seems that my refractometer is very consistent when the sample comes from the same vessel (nevermind beer, wort or water), it's no longer the case when I switch to a different vessel, even though the gravity reading remains the same. That's exactly my point. :/