Recently had a few batches with good yeast starters seem to stall out at 1.025-1.030…pilsner grain mostly, and not high OG. Tried adding some more yeast cake from a prior batch, and no activity. Its been “stalled” at mid gravity for a few weeks now. Is there anything I can do? I hate to throw more yeast at it if it wont in fact help.
Sounds like the problem isn’t yeast. First thing I’d do is a fast ferment test to confirm that. Since it’s happened more than once, maybe your thermometer is off.
If you’re using a refractometer, be aware that once fermentation starts the direct reading won’t be anywhere close to accurate. You need to enter OG and the Brix reading into a calculator to convert to SG. Also, before using a refractometer it not only needs to be zeroed with distilled water but you need to calculate the wort correction factor which is specific for your refractometer.
Count me in as thinking the probable culprit is an equipment issue. An all Pilsner wort that was properly converted in the mash will not finish in the upper 1.020s with any beer yeast unless your OG was super high (like 1.100 or higher)
Likely issues:
Using an uncorrected refractometer reading to determine FG
Hydrometer calibration is off. Confirm that it reads 1.000 in room temperature water. Sometimes the paper can slip inside and throw it way off.
Mash temps were way off. This is less likely to me because Pilsner malt will convert quickly even if you miss mash temps by 10 degrees. You’d have to be in the 130s or 170s to run into that kind of conversion issue.
I agree, check the hydrometer calibration. How does the beer taste?
Indeed, tasting the beer is the simplest way to rule in/out yeast issues. If it is truly stalled, it will taste sweet, thick, and cloying, and probably will have off flavors as well. If it has fully attenuated, it should taste like pretty normal beer, albeit a full-bodied one if that high FG is real. This would point to equipment issues (which is my vote as well).
If that high FG is real, you can add a vial of ultra-ferm to break down those unfermentable dextrins. Cold crash the beer when it reaches the FG you want to slow down the enzyme’s action.