Baltic Porter - High FG

[CJV8]

I've got a baltic porter in the fermentation fridge coming to the end of its fermentation schedule, however it's sat 8 gravity points above target FG for a week (1026 when the target is 1018). It's at 16°C at the moment, it had a cold start with a gradual ramping up of the temperature over a several weeks. The SG was 1085 so there's quite a high level of alcohol in there now. This is my first time using a lager yeast (Mangrave Jacks M84), which was done as a 1 litre starter, so I'm unsure what to do to try and drop the gravity a bit further.

I have temperature control so can heat or cool as required, but wondered about a small pitch of an ale yeast to restart fermentation? I have US05 to hand. Any suggestions of the best way forward?

 

[pilgrimhudd]

Just a quick look, I see that mj 84 has 72-76% attenuation so it's pretty close.. I think I'd raise the temp give it a stir and leave it for another week or so. What temp did you mash at, perhaps slightly too high?

 

[CJV8]

Mash was stepped, can't remember the steps but think it was something like 55, 65 then 72.

 

[Tanglefoot]

Not sure how much you pitched but Mangrove Jacks recommend 2 x packs
for higher OG brews, anything over 1.050 as I remember.
I've always just used one no problem but thats in 5% or less brews.

 

[pilgrimhudd]

Not sure how much you pitched but Mangrove Jacks recommend 2 x packs
for higher OG brews, anything over 1.050 as I remember.
I've always just used one no problem but thats in 5% or less brews.

Yeah good point.

 

[CJV8]

It was a single pack, but put into a 1 litre 1040 starter and run on the stirplate for 48hrs.

 

[CJV8]

I gave the porter a gentle stir, raised the temp to 20°C and nothing. Made up a 1 litre starter of SN9 wine yeast to see if it was the alcohol content (7.7%) that was part of the issue, but amazingly no action from that either. So it's on chill and will be bottled later this week.

My best guess is it's a mashing issue. I've not long made a HERMS pot and this is only my second brew with it. Could be that I'm doing something fundamentally wrong in step mashing as I've never had issues with single temp infusion mashing previously. The HERMS only came about due to a never ending need to tinker, and having a few spares laying around!