Left sample in hydrometer glass

[Scuba_Steve81]

I left a sample in the hydrometer vial just out of curiosity. The beer was more than likely on its last day of fermentation. It was 1.020 after 3 days fermenting. 8 hours later, it has dropped down to 1.012.

Did fermentation continue in the vial? If so, conceivably, could you pull a sample the day after pitching and leave it the entire time to know about when its done without continually pulling samples?

 

[pvpeacock]

Interesting question. Assuming the temperature of the sample didn't change, it would appear that fermentation continued to happen in the vial. Either that or you have a leak in your hydrometer and it will soon hit the bottom of the vial.

 

[bionut]

You don't have to continually pulling samples, just pitch, let it ferment for 1-2 weeks (for non big gravity beers) and after that take a sample. If you want to be sure you can take another sample 2 days after that, but i think it's overthinking.
In my mind a small volume of wort will ferment faster that the full volume. Don't have any explanation yet, i need to have some beers to get the wheels rolling.

 

[Scuba_Steve81]

It did change temp, but not enough to make more than a point of difference.

Fermenting at 62, room temp at 75.

I know to accurately do this I would need to keep them at the same temperature.

 

[jerbrew]

Essentially, yes good observations. This is a technique i've seen used a few times in articles when someone wants to know where their beer will end up. for example, 1.012 final gravity. The idea is to pull a sample after pitching and let it go on a stir plate at room temp. The beer in your flask, a growler could work for this too since i'm sure we all have a few of those, would finish fermenting faster but end at the same gravity (or pretty close to it). you could then take fewer samples from your fermenter reducing the risk of infection.

Here is a good example of a technique for dry-hopping using that method to figure out when the beer was nearing the end of fermentation (within the last 0.004 gravity).

http://homebrewacademy.com/experimental-dry-hop-technique/

Hope this helps/is intersting.

 

[jerbrew]

Also, a quick change in gravity reading like that could have been dissolved CO2 clinging onto you hydrometer and releasing as it was heated or got nudged. Not sure if you were looking out for that.

 

[GHBWNY]

After only 3 days in ferm, that's seems like an unreasonably quick drop in FG in that short length of time. Is it possible it may not have been as much an indication of fermentation as stratification? IOW, the measurable alcohol rose to the top and the debris settled out below the hydrometer? If so, your FG reading may be flawed. I'd have taken the hydro out of the tube, put my thumb over the end of the tube and mixed it up and then taken another reading and compare. Meanwhile, I wouldn't use it to monitor an entire batch until I was sure.

 

[Scuba_Steve81]

It is a hef, which ferments quickly from what I know. Dropping about 12 points every 36 hours.