Can I finish a stuck lager fermentation by pitching an ale yeast?

[Saint_Doyle]

I brewed up a high-gravity wort and racked it on top of a healthy White Labs Oktoberfest yeast cake (left in the bottom of a carboy from mid-gravity lager that previously inhabited the carboy). This is a trick I use in place of making a yeast starter.

OG: 1.130
stuck fermentation gravity: 1.070 (~8.5% abv)
target FG: 1.040
stored at 55' (optimum temp for this yeast) for 6 months.

My fermentation is stuck. I'm certain there were enough yeasts. This yeast is described on the White Labs page as having a "Medim-High" (sic) alcohol tolerance. I'm thinking that the ~8.5% alcohol content of the wort might have killed of the fragile little lager yeasts.

OK, enough rambling. The reason for this post: I'm considering pitching a well-aerated starter of California Ale yeast (High alcohol tolerance) in this to finish it off. However I'm worried that any residual lager yeasts might go awry and make off flavors if I stored this carboy at room temperature (non-lager temps). Can I finish off a lager at room temperature?

Alternatively, I'm considering using some Amalyse.

Forgive me if this question is answered elsewhere. I read several "stuck fermentation" threads but didn't see any specifically addressing my issue. Thanks.

 

[estricklin]

Perhaps the yeast weren't as healthy as you would have hoped?

1.130 is a BIG beer my friend, big like Ron Jeremy and big like China. At this point, I would say yes try a champagne yeast or something if your that worried about dropping it further. What kind of beer is this, does it have a lot of unfermentables in it?

 

[Saint_Doyle]

It's an imperial Oktoberfest/Double Bock sort of experiment. I tasted it and it is way too sweet as is. So, yes, I definitely want to drop the gravity down. To reiterate my main concern: I'm afraid that any residual lager yeast may not appreciate being stored at room temperature if I were to add in some ale/champagne yeast. Can I do that without pissing off the lager yeast? Or should I just make pitch an additional giant batch of lager yeast starter and continue to let it ferment at lager temps?

 

[estricklin]

I think your lager yeast gave up the ghost a long time ago, and I don't think the temperature is going to have a great effect on it at this point either. I've fermented lagers at 68F before so I don't see where temperature is a problem.

Try some a healthy big pitch of some type of beer yeast, or better yet a wine yeast. It probably isn't going to drop a lot more though so manage your expectations.

 

[Saint_Doyle]

I pitched 2 packets of dry champagne yeast into the carboy on the recommendation of my LHBS. I'll let you know how this turns out. I'm going to watch it and cold-crash it when the gravity reaches ~1.040.

 

[Smellyglove]

I've read and heard somewhere (I can not find the source right now) that champagne yeast isn't optimal for bringing SG further down in an already fermentet wort because the wort will most likely lack some nutrients which a beer yeast will do better than a c-yeast if the wort lacks this.