Lager with stuck fermentation

[John E Miller]

So I've been away for almost two weeks after putting down a bock. The original gravity was 1.074. I got home last night, and after 17 days in the fermenter the gravity is only 1.030 (target FG 1.014). Temperature has dropped from around 10C down to 6.5, and airlock activity seems to have ceased. Yeast I've used was Coopers lager yeast, harvested from previous batch of European Lager (and built up a bit with a 500ml starter). The batch is 15 litres.

The sample I've tasted is very sweet (duh). Pretty frustrating, but I hope to revive it. I have no fancy gadgets for temp control, just a microwave heat/wheat pack that I'm resting up against the side of the fermenter to try to wake the yeast up again, but might have to make another starter?

So - low temps, high starting gravity...  any ideas what caused this and where to go from here?

[Aussiekraut]

26 minutes ago, John E Miller said:

So I've been away for almost two weeks after putting down a bock. The original gravity was 1.074. I got home last night, and after 17 days in the fermenter the gravity is only 1.030 (target FG 1.014). Temperature has dropped from around 10C down to 6.5, and airlock activity seems to have ceased. Yeast I've used was Coopers lager yeast, harvested from previous batch of European Lager (and built up a bit with a 500ml starter). The batch is 15 litres.

The sample I've tasted is very sweet (duh). Pretty frustrating, but I hope to revive it. I have no fancy gadgets for temp control, just a microwave heat/wheat pack that I'm resting up against the side of the fermenter to try to wake the yeast up again, but might have to make another starter?

So - low temps, high starting gravity...  any ideas what caused this and where to go from here?

I guess the yeast has gone to sleep. 6.5C is rather low, even for a lager. You could try to up the temp back to where it is supposed to be and see if the yeast wakes up again. It may not hurt to add a little more lager yeast from a starter either. 

[Otto Von Blotto]

First thing would be to warm it up and see if it kicks off again. Lager yeast can work that low and lower but it may be dependent on the strain. The Coopers one might not go that low.

[John E Miller]

I've just rigged up a "heat belt" . Temp is at 8°C now, and the airlock is bubbling straight away, but I'm guessing that's from the air in the headspace expanding due to the heat. 

Edited July 20, 2020 by John E Miller

[DonPolo]

I'm having the same issues with a Cooper's Lager which I think cooled off too far when I went a way for a few days. I have let it rise to 21C because of other advice here and because the kit said the ideal range was between 21-27C. 

I understand that the yeast that Coopers supplies for this lager is at least partially an ale yeast anyway so it may not be wise to let it's temperature drop too low anyway.

It could be that the yeast in the Coopers European Lager is also at least a bit ale yeast. I seem to remember that on the kit it said that the European Lager should be brewed at a temp of around 14-16C which is way higher than what you were doing.

[Shamus O'Sean]

@John E Miller I have never done it, but could you sit the fermenter in a laundry sink with warm water?  Keep topping up/switching out to keep it warm enough to kick off fermentation again.  I am thinking even around 20-25°C.  Given your starting gravity, maybe you are at a point where it is ready for a diacetyl rest anyway .

[John E Miller]

@Donpolo yes, the Coopers original series lager just comes with ale yeast, but the European lager comes with a lager yeast. 

[Greenyinthewestofsydney]

58 minutes ago, John E Miller said:

@Donpolo yes, the Coopers original series lager just comes with ale yeast, but the European lager comes with a lager yeast. 

Yep. And not a bad lager yeast at that. The 7gm isn't anywhere near enough to do a true lager at lager temps which is why they tell you to do it at a higher temp.

[Titan]

This starter was too small for the SG. Minimum i would have pitched would have been from a 2l starter. I also have a Bock with similar SG at 23l volume and i pitched from a 4l starter.

[John E Miller]

On 7/20/2020 at 9:20 PM, Shamus O'Sean said:

@John E Miller I have never done it, but could you sit the fermenter in a laundry sink with warm water?  Keep topping up/switching out to keep it warm enough to kick off fermentation again.  I am thinking even around 20-25°C.  Given your starting gravity, maybe you are at a point where it is ready for a diacetyl rest anyway .

I'm not sure how I feel about submerging the tap in water... any chance of infection or something? I've also heard that applying heat directly to the yeast cake is not ideal, but I might give it a go if I can't do the job with my wheat pack. Can't get above 10°C. SG has dropped a couple of points to about 1.028, but I was hoping for a bit more than that by now.

[John E Miller]

On 7/21/2020 at 9:18 AM, Titan said:

This starter was too small for the SG. Minimum i would have pitched would have been from a 2l starter. I also have a Bock with similar SG at 23l volume and i pitched from a 4l starter.

Ok, so maybe build up another starter of yeast and send them in to finish the job?

[John E Miller]

On 7/21/2020 at 8:55 AM, Greeny1525229549 said:

Yep. And not a bad lager yeast at that. The 7gm isn't anywhere near enough to do a true lager at lager temps which is why they tell you to do it at a higher temp.

Good to know. What do you like about the yeast, and do you have any guess what strain it might be?

[Greenyinthewestofsydney]

Was clean and neutral at lager temps. Purportedly its mauribrew 497 which has a wide range of temps.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.brouwland.com/content/docs/050/050%20Biergisten%20Brewferm%20en%20Mauribrew/050.253.4-050.255.9_SPEC_EN_Mauribrew%20lager%20497.pdf&ved=2ahUKEwid3v7XzODqAhVUyzgGHQAXA9QQFjACegQIBhAK&usg=AOvVaw3olBErr8860T5pRYsd1eua&cshid=1595412100048

 

[John E Miller]

16 hours ago, Greeny1525229549 said:

Was clean and neutral at lager temps. Purportedly its mauribrew 497 which has a wide range of temps.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.brouwland.com/content/docs/050/050%20Biergisten%20Brewferm%20en%20Mauribrew/050.253.4-050.255.9_SPEC_EN_Mauribrew%20lager%20497.pdf&ved=2ahUKEwid3v7XzODqAhVUyzgGHQAXA9QQFjACegQIBhAK&usg=AOvVaw3olBErr8860T5pRYsd1eua&cshid=1595412100048

 

Cool, have you used it in different beers?

[John E Miller]

I made another yeast starter last night and it was frothing this morning, so I pitched it. The airlock is now bubbling away once more, so I'm feeling positive.

BTW, I think my target gravity was mistaken... the can instructions said expected FG was 1.014 when mixed to 23 litres, but I made it more concentrated at 15 litres, and mistakenly supposed the FG to be the same. After looking at a formula online I'm now expecting the FG to be 1.021. Not so far to go after all.