Alcoholic Ginger Beer - Second Ferment's Final Gravity Higher than Starting Gravity

[GBeerBrewer]

I've been brewing my own Ginger Beer for some time (Recipe ratio is a gallon of water:378 g sugar: 13 cm ginger:2 tbsp ginger beer plant) using a plant (SCOBY-like organism, not a ginger bug - mixture of ginger,sugar,yeast and water) and just recently decided that it'd be a good idea to start measuring the alcoholic content of my final brew. Making the ginger beer is a three step process:

i. primary fermentation (aerobic, in a cloth-covered jar with the ginger beer plant)[a three to four week process until the liquid reaches a pH of 3-3.5)
ii. secondary fermentation (anaerobic, in a glass carboy with an airlock and the GBP removed) [a process equal in length to the previous one]
iii. bottling (to induce carbonation) [a 4-5 day process before refrigerating, though sometimes I've let it go on for a few weeks to get the beer to drop a bit in sweetness]​

I decided to take my initial measurements after primary fermentation (before pouring into the carboy but after I've added about 15 grams of filtered fresh ginger juice, to kick up the spiciness a bit) and my final measurements before bottling since I figured that the anaerobic fermentation stage was when the bulk of the conversion to alcohol would take place (some definitely happens during the primary fermentation stage since the yeast in the SCOBY converts the sugars into alcohol that the bacteria can consume). Here are my measurements:
- October 4th (before 2nd ferment)

• pH:3
• Refractometer
  -Brix: 6.1
  -SG: 1.025
• Hydrometer
  -Sp. GR: 1.022
  -P.ABV: 4.3 %
  -Brix: 6

-October 25th (before Bottling)

• pH:3
• Refractometer
  -Brix: 10.9
  -SG: 1.043
• Hydrometer
  -Sp.GR:1.044
  -P.ABV: 6%
  -Brix: 11

Now, maybe I should've taken a measurement before primary fermentation but, still. It's quite odd that My final gravity is greater than my starting gravity, isn't it? This yields (nonsensical) negative ABV calculation!

What gives?

 

[griffi]

Maybe drink this one to sober up?

 

[Yooper]

Well, I’m sure you know this but if you didn’t add sugar, those readings just aren’t possible.

Since the refractometer is useless once alcohol is in the mix, I’d suggest trying another reading with your hydrometer. Make sure it reads 1.000 in plain water first, and then see what you have. We can tell you where to go from there.

 

[GBeerBrewer]

Well, I’m sure you know this but if you didn’t add sugar, those readings just aren’t possible.

Since the refractometer is useless once alcohol is in the mix, I’d suggest trying another reading with your hydrometer. Make sure it reads 1.000 in plain water first, and then see what you have. We can tell you where to go from there.

Gave it another go with both of them (even after what you said about the refractometer) and I got the same readings. Definitely reads 1.000 in plain water too. No sugar is added after primary fermentation (it's sweet enough even after bottling which is why, depending on how I want it to taste that month, I leave it to "dry out" and don't 'fridge the bottles until a couple of weeks after bottling). I can't even blame it on the starch from the ginger juice that is mixed in before secondary fermentation because the juice is left to stand until the starch forms a solid layer at the bottom of the jar and then the liquid is passed through a coffee filter before being added to the brew.

Any other suggestions for what might be going on?

I'll take a new set of readings with this month's batch (11/15 or 16th) and I'll be sure to take one right before primary fermentation starts for next month's batch (also 11/15 - 16th)

Maybe drink this one to sober up?

What're you getting at?

 

[augiedoggy]

I think it was a joke because your numbers posted dont make logical sense is all.. I wouldn't take it personal . That said I agree there is a mistake here as the gravity isn't going to go up on its own.

 

[GBeerBrewer]

Hmmm, gotcha. Yeah, I can't make heads or tails of it at all. Thought I must've misread the first time around but having taken the measurement thrice I can't come up with anything! Unless I took an incorrect reading the first time around (pre-anaerobic fermentation) and my backup (using the refractometer) was worthless because there was already some alcohol in it from the first fermentation?

 

[Yooper]

Hmmm, gotcha. Yeah, I can't make heads or tails of it at all. Thought I must've misread the first time around but having taken the measurement thrice I can't come up with anything! Unless I took an incorrect reading the first time around (pre-anaerobic fermentation) and my backup (using the refractometer) was worthless because there was already some alcohol in it from the first fermentation?

Yes, that is likely.

 

[GBeerBrewer]

Lets see how this plays out in a couple of weeks. Thanks for all the help so far.
I've got some more data to share, in case anyone is curious:
Measurements taken on

Oct. 25th - After Aerobic Fermentation, Right before starting anaerobic fermentation

• pH:3
• Refractometer
  -Brix: 11.6
  -SG: 1.043
• Hydrometer
  -Sp.GR: 1.042
  -P. ABV: 5.1%
  -Brix: 10

and

November 6th - In the Middle of Aerobic Fermentation

• Hydrometer
  -Sp.GR: 1.020
  -P.ABV:2.5%
  -Brix:5

The second set could be pretty useful in about 10 days, when I transfer that batch into anaerobic fermentation while the first set will be compared to the readings taken right before bottling that (discrete) batch. The numbers from the first set are similar to the readings I got after anaerobic fermentation from my first post so maybe there was an error in measurement.