Forst Dopplebock possibly/soon to be stuck fermentation?

[Jvid]

Hi all, I brewed my first dopplebock and first HG lager back on July 18th using the below recipe from byo.com:
(5 gallon/19 L, all-grain)
OG = 1.076 FG = 1.020
IBU = 22 SRM = 15 ABV = 7.5%

Ingredients
9 lbs. (4.1 kg) Munich malt (10° L)
4.75 lbs. (2.2 kg) Pilsner malt
2 oz. (57 g) dehusked chocolate malt (400 °L)
Saaz, Spalt, Styrian Golding, Hallertau Mittelfrüh or Tettnanger hops
German lager yeast

The brew day itself went fine as far as I can tell, OG was right around where it needed to be, but I did the brew after a work day and didn't finish up until 11:30pm at which point the immersion cooler had it down to 70°F and wasn't budging any further. I was tired and had work the next day, so i aerated the wort and pitched 2 packs of OYL-111 and put it in the fermenting fridge set to 45°F to get it down where it needed to be. 3 days later after no airlock activity and realizing I'd underpitched, I added 2 more packs of yeast and finally got it to take off. As of today I'm sitting at 1.027 gravity and there's still minimal airlock activity but I'm having doubts that it's going to make it down to the 1.020 FG. From the sample i pulled diacetyl is definitely present.
Coming from mostly ales i'm probably being overzelous.. Does this sound like a soon to be stuck fermentation? I'm planning on starting the diacetyl rest possibly Sunday night or Monday. Should gravity fall any further during the diacetyl rest?

 

[GoodTruble]

Is it possible there is leak allowing gas to escape somewhere other than the airlock? Sometimes just sniffing around will tell you.

The gravity reading doesn't seem overly worrisome. I would just proceed as intended.

 

[dmtaylor]

It's time to start the diacetyl rest right now. And leave it warm not just for a few days, but for a good week or two. Your patience and your higher temperatures will make the yeast happy, they'll finish the job and without diacetyl. Ideally you want to begin your diacetyl rest when apparent attenuation is 50%, i.e., OG 1.076 goes to 76/2 = 1.038. You're past that, so begin the rest now while there's still time for the yeast to be more active. They'll eat the diacetyl as a midnight snack kind of thing.

 

[Jvid]

It's time to start the diacetyl rest right now. And leave it warm not just for a few days, but for a good week or two. Your patience and your higher temperatures will make the yeast happy, they'll finish the job and without diacetyl. Ideally you want to begin your diacetyl rest when apparent attenuation is 50%, i.e., OG 1.076 goes to 76/2 = 1.038. You're past that, so begin the rest now while there's still time for the yeast to be more active. They'll eat the diacetyl as a midnight snack kind of thing.

Okay, I'll start the rest now. Should I be shooting for ~58°F or go up to 65°F? I've had the fermenter between 52° and 54° the past week.

 

[dmtaylor]

I'm a room temperature guy myself, I'd bring it all the way up to 70 F. Or 65 F if you're concerned. The exact temperature honestly doesn't matter. A few degrees will make the yeast happy, which is all you need.

 

[Jvid]

I'm a room temperature guy myself, I'd bring it all the way up to 70 F. Or 65 F if you're concerned. The exact temperature honestly doesn't matter. A few degrees will make the yeast happy, which is all you need.

Thanks! Let's see how this turns out.

 

[AlexKay]

Obligatory "how are you measuring gravity" question.

If with a hydrometer, you're probably mostly accurate, though you could check calibration and temperature.
If with a refractometer, make sure you're using a calculator to correct for the presence of ethanol.
If with a Tilt, OG is correct but FG can be significantly off, when the sensor gets yeast gunk (this is the technical term) on it.

 

[Jvid]

Obligatory "how are you measuring gravity" question.

If with a hydrometer, you're probably mostly accurate, though you could check calibration and temperature.
If with a refractometer, make sure you're using a calculator to correct for the presence of ethanol.
If with a Tilt, OG is correct but FG can be significantly off, when the sensor gets yeast gunk (this is the technical term) on it.

It is a tilt hydrometer so gunk may very well be an issue. If before i transfer to lagering serving keg I retrieve, clean, and re-sanitize the tilt I should be able to get an accurate fg reading, right?

 

[dmtaylor]

Yes, the Tilt never measures FG very accurately. It's a fun toy, which I love, but I don't expect it to be very accurate.

 

[AlexKay]

It is a tilt hydrometer so gunk may very well be an issue. If before i transfer to lagering serving keg I retrieve, clean, and re-sanitize the tilt I should be able to get an accurate fg reading, right?

Yes, a clean Tilt will give a good reading. The thing to keep in mind for during-fermentation monitoring is that it will tell you the relative speed and progress of fermentation, but in terms of the endpoint it can absolutely be off -- in either direction -- by five points or more.

 

[Deadalus]

Yes, a clean Tilt will give a good reading. The thing to keep in mind for during-fermentation monitoring is that it will tell you the relative speed and progress of fermentation, but in terms of the endpoint it can absolutely be off -- in either direction -- by five points or more.

Right, look at the curve to see whether you are leveling out (approaching an asymptote). That would indicate the yeast is done.

Pitching the yeast into the 70F wort may have been an issue but for sure in my opinion you were running too cold at 45F. The recommended range for that yeast is 48-55F. It says its liquid substitution is WLP-833, which I have used before and I never run colder than 50F. Lager yeasts tend to get slow under 50 in my experience.

 

[Jvid]

Right, look at the curve to see whether you are leveling out (approaching an asymptote). That would indicate the yeast is done.

Pitching the yeast into the 70F wort may have been an issue but for sure in my opinion you were running too cold at 45F. The recommended range for that yeast is 48-55F. It says its liquid substitution is WLP-833, which I have used before and I never run colder than 50F. Lager yeasts tend to get slow under 50 in my experience.

Sorry I should have specified. 45° overnight and the upped to 50° the next day. Just wanted to get that temp down from 70 asap.

 

[Deadalus]

Sorry I should have specified. 45° overnight and the upped to 50° the next day. Just wanted to get that temp down from 70 asap.

OK. You pitched high and dipped under then back up some. I've only had my tilts for about 6 batches and just one lager, although I lager a bit in general. I've been somewhat surprised so far at the fermentation speed showing on my tilt data as the gravity drops more strongly than I imagined. I think I've thought of it as more of a linear situation but it's not. Anyway, what does your tilt data show for activity in the first three days? How did the gravity change before the repitch and how quickly did your temp drop?

 

[Jvid]

Well I cleaned the tilt and after a weekend at 68°F I'm reading 1.025. Pretty sure this is going to be it. I now have a stir plate coming and a fresh reminder how much more yeast I need to be pitching for lagers lol.

 

[dmtaylor]

Have you calibrated the Tilt versus a traditional hydrometer? The Tilt still is only accurate if you have checked it against another traditional.

 

[AZ Maverick]

Yes, the Tilt never measures FG very accurately. It's a fun toy, which I love, but I don't expect it to be very accurate.

Boy, I have a totally different opinion.
I have two Tilt hydrometers that I calibrated against my hydrometer before using them.
I have been using them for over a year now and they work perfectly and always agree with my hydrometer - in fact I don't even use my hydrometer anymore, I use my refractometer (which is also accurate) and my Tilts.
Here is my Tilt plot of a Dopplebock that I am currently fermenting: