FG increased dramatically during fermentation

[Donoroto]

I use a Tilt to monitor fermentation. A Hefeweitzen I brewed last Wednesday was doing just fine, down to 1.023 at 11:30 this morning. For unknown reasons the Tilt Pi (a Raspberry Pi that logs to Google Sheets) went offline after that, and when I rebooted it some 4 hours later, the SG was reading 1.036.

Even shaking the fermenter a little, the SG didn't change, still 1.036. Screenshot of the data below.

I am inclined to just ignore it, but can anyone think of reasons why the specific gravity would increase so dramatically and suddenly?

 

[J A]

Pull a sample and check it with a hydrometer. Gravity doesn't go up unless you add sugar, it's that simple. If you didn't add anything, it's a measurement error. Maybe the battery somewhere need looking at. Maybe something is interfering with the transmission from the Tilt unit.

 

[dmtaylor]

The Tilt just plain is not very accurate near end of fermentation when it has a lot of schmutz stuck onto it. With frequent rocking of the fermenter I can keep it accurate within 0.002 of a real hydrometer. Otherwise, it is not very accurate at the end. But you can still rely on it to know when fermentation is over. I mean eventually it should stabilize, even if it doesn't hit the right number.

 

[Mark Farrall]

I'd be guessing it's either touching something in your fermenter (bag, tube, etc.) or it's had a chunk of gunk attached to it, as dmtaylor mentions. If you can tell where in the fermenter it is I knock on the side of the fermenter to move it away from various things I have in there. Otherwise gentle swirling can sometimes remove crud.

It will still be accurate at telling you when fermentation is done, but the number is now off and you will need to use a refractometer/hydrometer after fermentation is finished to tell you the real number.

It doesn't happen very often for me. Probably only one batch in 10-15 where it isn't easy to move/remove whatever is creating the incorrect tilt angle.

 

[Bubba Wade]

I've used the Tilt for about two years. One of the oddities you see is an occasional jump in SG. This appears to be due to bubbles sticking to the Tilt at various times during the fermentation and causing the Tilt to float higher. Then the bubbles release and the reading is correct again.

I've checked the Tilt on both OG and FG against a hydrometer on a couple of dozen batches. It's never been off more than +/- 0.002.

 

[Donoroto]

Yep, I am in agreement: fermentation is fine, tilt is profoundly unhappy. Normally I have another couple days, I will let it go until then and, once it stabilizes and sits a few days, keg it and see what happens.

I probably should take a sample as well just to see what's going on. More soon

 

[Bubba Wade]

Here’s a shot from one of my batches. As you can see, SG jumped and then settled in.

However, this seems to usually occur in the first few days.

 

[west1m]

I also use the Tilt. The jump after a couple days happens often then settles down a day or so later. My last batch NB Legend of Latura , kind of stopped dropping after the spike in SG. I just gave it a good swirl and everything went back to normal.

 

[Donoroto]

I can only guess that the tilt was physically unhappy.

To me, it seems the earlier excursion down to 1.023 was the error, and the 1.036 reading was correct. I took a sample, Tilt says 1.026, hydrometer says 1.028. (The small error on the tilt is typical of my experience; I have never calibrated it).

I tasted the sample and it was as expected.

 

[mil;o1512]

I just brewed an IPA and the fermentation went from 1.501 to 1.010 in 36 hours. The tilt showed the entire fermentation process and I am now wondering should I bottle or wait a while say - a week. '
My last IPA fermented from 1.062 to 1.011 in two days - on that one I waited a full week or 7 days total as I was dry hopping. The tilt gives you so much insider information as to what you wort is doing and if your yeast starter was active enough during the fermentation process. I like the tilt - no mess, no opening and closing, no guessing - just great data.

 

[Mark Farrall]

I wait for 2-3 days of no movement and then package as soon as it's convenient. If I'm dry hopping I give it an extra day or so as it sometimes kicks off a bit of extra fermentation.

 

[Donoroto]

Give a finished fermentation a few days as a Diacetyl rest before packaging.