Final Gravity Help - Three Instruments, Three Different Readings

[Supabrew]

Hi Guys,

Just brewed a 5 gallon batch of hefeweizen on Sunday. Used a nice, healthy 1.6L yeast starter and it fermented beautifully. Today, ~2 full days later, there is virtually no activity in the blow-off (fermenting this in a Ss Brewtech Unitank 7) so I figured I would check to see if fermentation is complete... I was aiming for a FG of 1.009.

OG: 1.047 according to refractometer reading (11.6-11.7 brix)

I took three readings at 62F using three tools as follows and am looking for help puzzling out the results:

1. Refractometer measured approx. 5.75 brix--definitely not a clear line--(using calculator, it puts it at 1.009 FG)
2. LD Carlson Triple Scale Specific Gravity: 1.014
3. True Brew Triple Scale Specific Gravity: 1.020

From my OG, these readings range from a measly 3.54% ABV to a more respectable 4.99%.

Any thoughts on why the readings are so different and which one to trust?

 

[Diver_Alan]

Hydrometers are best once alcohol is present. You need to check each Hydrometer for the temperature it is celebrated for. Then get some distilled water that is the correct temperature and check your reading. It should be 1.000. If the calibration is off adjust your readings by that amount.

 

[jturman35]

Dang I never touch a beer for at least 2 weeks.

 

[Supabrew]

Hydrometers are best once alcohol is present. You need to check each Hydrometer for the temperature it is celebrated for. Then get some distilled water that is the correct temperature and check your reading. It should be 1.000. If the calibration is off adjust your readings by that amount.

Yes, I read up on refractometers and heard that they aren't ideal after alcohol is present. The refractometer is a new toy, so I wanted to see how well the calculators across various sites performed to "correct" for alcohol presence. That's why I busted out the two hydrometers I had laying around to compare which led to my surprise!

I did cool some RO water down to 60F (don't have distilled laying around, but RO should be pretty close) and can confirm that the LD Carlson Triple Scale is right on the money... looks like my brew is at 1.014 after two days. I'm going to let it keep going (the plan is 62F for three days, 65F for three days and 68 for five days) so perhaps it will continue to ferment a bit even if the brunt of it has completed already.

Dang I never touch a beer for at least 2 weeks.

I traditionally haven't either, especially in a bucket ferment, but since it's in a conical that has a sanitary sample valve, it makes it really easy to pull a little beer to check on the status of the fermentation. I hit it with a little StarSan from a sprayer and draw a little until I hit the FG (or come close) in BeerSmith.