Cold Fermentation method keeps failing me (stalling)

[Nick_D]

Hello everybody, this is my first post here, thank you for taking to time to read and answer.

In the past 4 months, I have dumped 3 whole batches of different lagers down the drain. Very upsetting. Basically, after my brew has reached the 1.5 plato to FG (determined by FFT) and I have racked for spunding, the gravity lowers a little further over a week or so, but stops very short of reaching FG.

More specifics of two of my batches that are experiencing this problem currently:

1: Helles (lodo brew method)

- FFT finished at 1.009 (O.G 1.044)
- Chilled to 5.5C, and pitched approx 40 million cells per ml of wort (overpitched) WLP838
- oxygenated with pure oxygen through 0.5 micron stone, 1.5 liters per minute, for 1.5 mins. I do not have an oxygen meter, and cannot afford one in the near future.
- Allowed fermentation temp to rise to 8C over 48 hrs.
- at 50% attenuation, I lowered temp by 1C per day to 6C, at which time it was approx 1.4 plato above FG (1.015)
- racked to keg for spunding (noticing the beer was much clearer than I expected), and continued to lower temp by .5 C per day until reaching 3 C. Held there for 1 week and checked SG. In one week it had only reached 1.014, and the spudning pressure had only climbed 1 PSI. So I took it out and let it rise to room temp (15C) and let it sit there for a week. It has not lowered in gravity and is still sitting at room temp.

2: Märzen (lodo brew method)

- FFT finished at 1.012 (O.G 1.054)
- Chilled to 5.5C, and pitched approx 35 million cells per ml of wort (overpitched a little) WLP838
- Instead of using pure oxygen, I shook the fermenter very vigorously for 5 mins, fearing the batch of helles may have been over oxygenated.
- Allowed fermentation temp to rise to 8C over 48 hrs.
- At 45% attenuation I did not lower the temp, and maintained 8 C to avoid stalling the yeast.
- at slightly above 1.5 plato to FG (1.021), I racked to spunding keg and maintained 8C, intending on holding this temp until FG was reached. I set the spunding pressure low (0.3 BAR) just to keep a good seal, and the beer produced plenty of CO2 during a week of spunding at 8C. However, it only reached 1.017 in this time, and 6 days later, is still at 1.017. There is clearly some kind of activity, as the beer is still very slowly making CO2, but the FG is not moving.

What am I doing wrong here? I realise if I leave the Märzen to go at 8C, it may get lower, but it doesn't look good. The beer is still cloudy with yeast in suspension, but they are not doing anything.
Did I over pitch both times? The estimates I gave could be low. I may have pitched up to 30 % more yeast than those numbers. Air lock activity began very quickly both times (within a few hrs), and krausen foam in less than 12 hrs.
Can I save either batch?? I'm very fearful of repeating the same mistakes, on the next batch, and being in the same position again.
If I could, I would leave the beer on the main yeast until reaching FG, but then I can't spund, and may have oxidation issues when transferring. I really want to get this method to work.

Sorry for the super long first post. I just wanted to be as informative as possible.

Thank you for being patient, and for your assistance.

Kind regards,

Nick

[Bryan R]

Shaking for 5 minutes is going to net you little to no o2.
Try this.
Using pure o2, Ferment at 8c. When gravity reaches 7ish Plato drop to 7c. When gravity reaches 6p drop to 6. You are spunding way too early so wait until 3.5p, drop temp and HOLD 4-4.5c UNTIL fg is reached. THEN step down. Until you get your fermentation properly dialed in do not drop below 4c before EVG is reached. Not every Brewer Joe can do cold fermentations out the gate. You have to turn into a yeast whisperer.

[Nick_D]

[Bryan R]

Anything sub 14p. With the spunding and the yeast rousing you when that do that 9 times out of 10 I am dead on with my FFT(Honestly I don't do FFTs anymore because I only brew the same 4 beers the same way, every time), but when I did this was the case. But for my example, we'll call it a Helles.

[Nick_D]

[Owenbräu]

I just rely on what is in suspension. What has flocculated out already isn't much help in finishing off the last few gravity points. If you wait too long, then yeah, go ahead and grab a little bit of everything off the bottom.

I tend to wait until 1P of remains extract and top off with forced carb as needed. I'm gonna have to hit the keg with CO2 eventually, so I'm more concerned with reaching terminal gravity than ensuring 100% of the carbonation comes from spunding.

[Bryan R]

Same here. Only using what's in suspension.

[Nick_D]

Thanks for your advice Bryan and A.Abbey. I am brewing a dunkel next using the classic warm method for dunkels. Will adjust your recommendation for temp adjustment vs degrees plato to reflect the slightly warmer temps. Hopefully I have more luck this time! am trying to brew a bunch of beers for an Oktberfest party I'm throwing at my house in a few months. A Pils, Marzen and Dunkel. I will let you know how it goes.

thanks again.

Nick

[Nick_D]

So the dunkel is fermenting away. Pitched at 8C as per the traditional warm schedule, ramped up to 11C over 3 days, and am now cooling gently by 1 C per day.

O.G was about 1.049, FFT is still showing very slow activity and seems to be hovering around 1.016 (it's cold here currently, 14C average ambient temp inside). Hopefully it will come down another point or two. That's pretty low attenuation though, I was hoping for more like 1.012.

The grist for the 19L batch was:

Weyeramnn munich II 4.7 kg
Weyermann carafa special II 0.15 kg

Mash was 60 mins @ 62C, Decocted approx 7L to raise the mash to 72C, then 60 mins at 72C. Pitched approx 350 billion yeasties, and aerated with pure oxygen.

If the F.G is 1.015, will this be any good as a dunkel? Is that in the ballpark? I Imagine it will be rather sweet....

Thanks!

[wobdee]

With all that Munich II it may have trouble attenuating much further. I like to throw in 15-30% Pils into my Dunkels to help out. I got one fermenting now that's 75/Dark Munich, 20/Pils, 4/cararoma, 1/carafa III. I did basically the same mash as you and my FFT the other day was down to 1.010 from 1.052.