Possible reasons for a negative ABV?

I 'completed' my first beer fermentation a few days ago. From the initial and final specific gravity, I ended up with a ABV of -120%. I'm really interested in finding the reasoning for this since it doesn't make any theoretical sense. Has anyone had this issue before.

I didn't do the calculations wrong but it is possible I recorded the specific gravity incorrectly. Although I did double check at the time, so I don't think so.

I did accidentally add the yeast at 26oC as I wasn't aware which temperature it should've been added initially. Could this have resulted in a negative ABV?

 

What were the readings you took?

 

As a guess you reversed OG and FG and missed a 0 in the FG number.. instead of say 1.056 you used 1.56. Calcuator here that will do it for you https://www.brewersfriend.com/abv-calculator/

 

I agree that we need the readings.
MaryB' s theory sounds good, the numbers would either confirm it or give other clues?

 

The readings were OG = 1.038 and FG = 2.3 (It ended up being -165%, not -120 as my post says). Switching the OG and FG wouldn't change anything as a +165% ABV wouldn't make sense either. Nor would reading the right number wrongly (The number is very off, not close to where it should be). The only thing that makes sense to me at this point would be the completely wrong number was recorded.

 

FG was likely 1.023.
Thats quite a high value(ideally it would be around 1.008) and indicates fermentation was not complete.

 

Your FG reading is an error. When you get a reading like that you will soon realize that the yeast cannot increase the sugar content so that high reading is impossible. From there on your calculations were wrong. Garbage in, garbage out. Take another reading and see if you don't get something much lower. Once possible cause for such a high reading is your hydrometer wasn't really floating in the wort but was resting on the bottom of the sample tube.

 

Is it possible the 2.3 reading was read off the balling scale instead of the specific gravity scale. The 2.3 on the balling scale would line up with approximately 1.010 on the specific gravity scale. This would be a normal final gravity for an American ale yeast.

 

Negative ABV isn't a thing. It's not even possible. You either have alcohol present or you don't. I think flars' explanation is most likely what happened, but it was most definitely a measurement error of some sort.

 

This seems like a perfectly reasonable explanation for a multi-scale hydrometer.

 

If you drink to much negative alcohol, you may become knurd. You have been warned!

 

This is great. Just chug three of them before driving home from the Pub. No wurries orificer.

 

And you get your wife back, your dog back, your job back...