German Brewing

Are you performing your FFT with bread yeast or with a sample from your beer after you've pitched the lager yeast?

Are you using a finishing gravity hydrometer? Refractometer calculations can vary by a whole percent.

Take a sample of your beer that seems stuck, put it in a sterile jar of some kind and let it warm up to room temp (or warmer). If it finishes out, then time and temperature is your issue. If it doesn't, then explore other rabbit holes.

Yeah, if you are trying to nail the textbook cold ferment, then don't taste it for a month. It takes time and you'll be pre-maturely frustrated.

I don't do the ultra-cold ramp down for secondary fermentation anymore, as I get better flocculation, clearer beer and less yeast in the keg if I let it go to terminal as I am dropping from 9C to 6C. It doesn't get to cold-lager until after EVG. I'm finding yeast in the serving vessel is more damaging than not following the Narziss secondary fermentation profile.

Narziss mentions that oxygen in excess of 30mg/l should be avoided.

For cold fermentation a DO meter should be high on the list (that's why I initially bought one).

There are factors that can influence fermentation tremendously. Here is an example.

OG: 12.5%
WLP: 838
Pitch: 5 Celsius
Main: 7 Celsius (day 3, for 4 days)
Transfer: 6C

The beer developed beautifully. Suddenly, it started to turn badly. It wasn't nice at all. Loads of things were suspected, autolysis amongst them. I kept the beer on schedule and was finished after 8 weeks. The end result was stunning!

What happened? That's a good one. I exclude autolysis because that is permanent damage. I did ramp down a bit too fast and the yeast really doesn't like it at lower temperatures. As one goes lower the temperatures need to drop even more carefully.

I think I had a bit of thermal stress or I was simply tasting by-products that weren't decomposed yet. I could have had a lot of unattractive tasting particles in suspension as well. Hard to tell w/o lab analysis.

So, don't dump. For all it's worth you simply didn't give the beer enough time to finish. It takes a bit of "Fingerspitzengefuehl" but thats the fun of it!

Hope this helps

I cannot tell what schedule to use. Eventually one ends up at -1C in classic cold.

It may go a little faster and clear up quicker if you set the lower limit to +1.5C - I'd drop the temperature veeeery slowly. Like 0.2C per day max.

You need to find what works for you and your setup.