Need advice for stuck fermentation

[Yonny]

Hi- I need some advice on what to do with a pilsner that's stopped a bit short of the finish line during fermentation.

All grain batch: 10# pilsner malt, 1#munich 0.5# carapils. Complete recipe is here:
https://shar.es/amHkCk
Using Wyeast Bavarian Lager
OG 1.051

I created 1liter of starter with the smack pack, pitched at about 60f. Signs of active fermentation within 18 hours.

I have a hard time maintaining lager temps in my basement... My finished basement prefers to be between 65-68f. I am using an outdoor shed (Ambient temperature 10f-50f) and I'm using a heating pad on my carboy and a thermowell and regulator to apply heat as needed. Using this setup, I fermented for 7 days and maintained pretty good temp control between 49f and 52f. I racked to a clean carboy and continued in the low 50's for 7 more days. At 14 days, it was down to 1.031 (OG was 1.051). I clicked up the temp to 68f and held it there for 6 days, planning to crash to 35f. After 6 days at 68f the gravity is now 1.028 with no signs of fermentation. The target FG for this brew should be about 1.013

Want to get feedback... What should I do?
Crash as planned, RDWHAHB?
Keep heat at 68f for a few more days?
Try to restart the yeast somehow (yeast nutrient? Stir the yeast?)

Also wondering if anyone can spot anything that I missed.

Thanks

 

[doug293cz]

Are you by any chance measuring SG's with a refractometer?

Brew on

 

[isomerization]

Why did you rack off primary so soon? You likely lost most of your actively fermenting yeast doing that.

 

[Eric_S]

How are you controlling the heating pad? With a controller?

Also a 1 liter starter is a big under pitch, even with 96% viable you needed a 2 liter starter. But you more likely needed an even bigger starter because 96% is like a week old from packaged. Use a calculator like http://www.brewunited.com/yeast_calculator.php

 

[SoCal-Doug]

Sounds to me like the yeast is struggling. Low pitch rate plus racking it before it was done. At the lower temps, cell division is really slow. 2206 (im assuming that's what you used) is not a big attenuator, but 1.028 is still quite high. Typically for a lager, I forget about it for at least two weeks. My assumption also is you used a hydrometer to check it and not a refractometer. If not, stop, go back and test it with a hydrometer.

Option 1: Let it keep going, consider bumping it to 65F ish. Check it again in a week
Option 2: Pitch more yeast, then use option 1

If you used 2206, you'll want a d-rest, so the warmer temps will achieve that plus give the yeast a more active environment to do their deed.

 

[Yonny]

Are you by any chance measuring SG's with a refractometer?

Brew on

Hi Doug - thanks for checking in... I started using a refractometer about 3 batches ago because I wasn't getting reliable readings with my hydrometer.

 

[Yonny]

How are you controlling the heating pad? With a controller?

Also a 1 liter starter is a big under pitch, even with 96% viable you needed a 2 liter starter. But you more likely needed an even bigger starter because 96% is like a week old from packaged. Use a calculator like http://www.brewunited.com/yeast_calculator.php

Thanks Eric - For this batch I invested in an Inkbird controller with a temperature probe. I'm letting the controller turn the heater on as needed, letting the freezing outdoor temps (Eastern Massachusetts in Jan/Feb) to keep it from getting too warm. This is my first time using this setup, but it seems to be keeping temps pretty reliably where I've been setting them

I brew >90% ales (only three lagers in past two years) and the starter rate worked fine for that, but now that I read a little more I see that higher pitch rates for lagers are recommended... Live and learn. I appreciate the feedback.

 

[Yonny]

Why did you rack off primary so soon? You likely lost most of your actively fermenting yeast doing that.

Thanks - I've been brewing for quite a while, but >90% ales (only a few lagers in past three years). I read in a post somewhere (can't find it now... damn) to rack lagers off of the yeast bed after either krausen subsides or 7 days, whichever happens later (this to avoid diacetyl accumulation). My krausen subsided about 6 days in, so I racked at 7 days. I'm definitely reconsidering that for my next lager.

Thanks for taking the time to respond.

 

[Yonny]

Sounds to me like the yeast is struggling. Low pitch rate plus racking it before it was done. At the lower temps, cell division is really slow. 2206 (im assuming that's what you used) is not a big attenuator, but 1.028 is still quite high. Typically for a lager, I forget about it for at least two weeks. My assumption also is you used a hydrometer to check it and not a refractometer. If not, stop, go back and test it with a hydrometer.

Option 1: Let it keep going, consider bumping it to 65F ish. Check it again in a week
Option 2: Pitch more yeast, then use option 1

If you used 2206, you'll want a d-rest, so the warmer temps will achieve that plus give the yeast a more active environment to do their deed.

Thanks Doug - I'm going to keep it at high sixties for the rest of the ferment and see if I can squeeze out a couple more points. I appreciate your advice.

 

[SoCal-Doug]

this to avoid diacetyl accumulation

Just to help a little... diacetyl is soluable and will be in the solution, not just the yeast cake. to get rid of diacetyl, you want the yeast to be active and the temperature to be above 64F for two to three days toward the very end of fermentation. The yeast will "clean itself up". This is called a diacetyl rest or "d-rest". You definitely want the yeast there to get rid of diacetyl.

The concept of racking is more for other off flavors developing, such as fatty acids decomposing and turning to a soapy tasting stuff. Racking and secondary's are becoming less popular as we learn more about off flavors and how to avoid them. Many consider transferring to a secondary more risk (infection) than gains.

 

[doug293cz]

Hi Doug - thanks for checking in... I started using a refractometer about 3 batches ago because I wasn't getting reliable readings with my hydrometer.

If you use a refractometer for measuring SG after the start of fermentation, the alcohol present will affect the reading (reading will be too high). There are correction calculators available (link1 link2) that will give you a reasonable estimate of the actual SG. It is recommended that you use a hydrometer to get the most accurate FG readings.

Using the calculator in the second link (and this SG to Brix converter), your estimated FG is 1.016, compared to your apparent (refract obtained) FG of 1.028.

Brew on

 

[Yonny]

If you use a refractometer for measuring SG after the start of fermentation, the alcohol present will affect the reading (reading will be too high).... Using the calculator in the second link (and this SG to Brix converter), your estimated FG is 1.016, compared to your apparent (refract obtained) FG of 1.028.

Brew on

Wow, Doug - that's a big swing! It also explains a lot as I brewed two ales last month and the fermentation bottomed out in mid 20's and well short of expected FG... I assumed it was something wrong with the dry yeast that I used. I went back and recalibrated the measured FGs using the correction above and they both landed right on target. Thanks for sharing!