Cellar Science Berlin Dry Yeast- Won't Stop

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Dec 30, 2015
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Farmington Hills, MI
I'm brewing a light lager, and using Cellar Science Berlin dry yeast from MoreBeer based on their suggestion. I'm not a dry yeast guy, and I've never used this yeast before. I oxygenated the wort (stirring oxygen wand with bottled O2 for 1 minute), and directly pitched two packets of their dry yeast into two 5.5 gallon batches. Technically I brewed an 11 gallon batch, and then split the wort between two FermZilla All Rounders to compare pressure fermentation vs. cold.

Setting aside that fermentation experiment for the moment, the yeast just won't stop dropping the gravity. I have a Tilt in each fermentor. My experience is typical with others, and the absolute value of the SG reading on the Tilt isn't that important, but I look for flatline for 3 days (no gravity drop). The problem is these beers are going on 19 days in the fermentor, and as I check my Tilt, I see an ever slight downward slope to the gravity. It drops about 1 point every 24 hours. I don't want to prematurely pull the plug if the yeast are still doing something, but am surprised that this is still going on.

The grain bill is mostly Pilsner malt, just some bittering hops in the kettle. Ground water in Michigan is cold this time of year, so I was able to get the pressure fermentation down to 62F and it sat there stable in my basement without using any cooling mechanism. I then gradually raised the temperature as I thought I was nearing "the end". It fermented with no pressure for the first 24 hours, then I dialed up the Spunding so it would hold 14 psi. My cold ferment sample I kept cold with the help of a Cool Zone Brewing jacket, and it fermented at 50F with no pressure. When it got to where the gravity was nearing predicted FG and Tilt trace was starting to flatten, I dialed up spunding to hold about 4 psi of pressure and it has sat there since.

My question is if anyone has used this yeast before, or experienced this sort of behavior? I'll normally get my 3 days of flat SG on Ales in 7 days, and Lagers fermented cold at 14 days. At this point, assuming the gradual drop stops for the next two days, these guys will be a new record for me at 21 days.

You have to remember, yeasts are a living organism...no matter what we do or how we treat them they are going to do what they do and sometimes we don't have any control.

My recommendation would be to double check the gravity with a hydrometer...the Tilt isn't perfect technology although its getting there.

Once you check and confirm gravity you can make your next move.
A hydrometer shows you the relative density of the mixture. Anything that makes it float higher will show that it is denser.....or is being held up. Since your tilt hydrometer is floating in the fermenter we can be pretty sure it isn't sitting on the bottom but what about some krausen stuck to it that is slowly coming off or some CO2 bubbles? Only believe the tilt hydrometer just so much, then get a second opinion.