Possibly stuck fermentation? Need help

[Brewshna]

Hi everyone,
we brewed a Imperial Chocolate Milk Stout on Jan 24th. Well at least we tried to.
Our OG should have been at 26 but was at 24 (we luckily also used maple syrup, that wasn´t planned originaly, for that bit of extra strength). We´d rehydrated our 5 packs of S04 yeast before including it. The fermentation started of just as it should. After one week of action everything stopped. Now we´re at 12,5 P instead of the planned 8 P.
Any ideas? Thanks in advance.
For more details here´s the recipe Brewfather

 

[RM-MN]

Are you using a refractometer? Unless you use a correction factor they read high when alcohol is present.

 

[Brewshna]

Using a hydrometer, used a refractometer for the OG reading

 

[Brewshna]

Don't understand what could have gone wrong after a Fantastic start to the fermentation. massive CO2 development. I've tried shaking, warming it in a 22C room. 5 packs of yeast is surely enough. rehydrated in Wort. since then I've used Lall brew yeast, they say hydrate in sterilized water only. don't know if that could cause a problem

 

[IslandLizard]

It may need more time. Still see any fermentation activity?
What temp did you ferment at? What temp is it at now?

Other thoughts:
You mashed pretty high at 68C (154F). In high gravity beers that compounds, with other unfermentables already in the wort. Even more so if the actual mash temp was say, 2 degrees higher. How sure are you it was kept close to 68C?

5 packs or S-04... That can't be the problem then.

I had a 1.092-some (22 °P) Old Ale end up at 8 Plato, using 2 packs of re-hydrated S-04.
10 others who brewed the exact same recipe came in at 4-5 Plato. Whatever I tried, it remained at 8P.
It may have stalled due a temp drop at some point, S-04 can be a bit finicky there.

 

[Brewshna]

activity has been 0 for 10 days or so.
rather sure about the 68C, using a brew monk wich is +-0.5C when I've double checked. We did a reiterated mash, split in 2.
Fermented at 17C,should be fine for S04.
Now it's at about 18-19C.
It was sat in my cellar, so there was shouldn't be any massive temp changes.

 

[Brewshna]

We did have the problem that we were no where near the planned Pre Boil Gravity, we think we crushed the grain to large. So we added some maple sirup to bring gravity up a bit, still didn't reach the planned 25.9P.

Maybe we should pitch some yeast and see if it helps. Only have 1 pack of lallemand Nottingham yeast on hand.

 

[IslandLizard]

We did have the problem that we were no where near the planned Pre Boil Gravity, we think we crushed the grain to large. So we added some maple sirup to bring gravity up a bit, still didn't reach the planned 25.9P.

Maybe we should pitch some yeast and see if it helps. Only have 1 pack of lallemand Nottingham yeast on hand.

Mash efficiency goes down with higher gravities, it's part of the process. A reiterated mash is good strategy for higher gravity brews, but there are limits, while efficiency still suffers, not much you can do about that. Many will use the (very high gravity) first runnings only for the big beer, then brew a session beer from the second runnings (parti-gyle).

You should have plenty of yeast in there already to finish it.
You're also at around 6% alcohol right now, it's not a very conducive environment for a new yeast to take over from there. Even for Notty.
I'd first warm it up a few more degrees, rouse the yeast (prevent oxygen ingress and resulting oxidation) and prevent any temp drops. See if it resumes.
Meanwhile you can make a relatively small (1.5-2 liter) 1.040-1.050 "starter batch" with the pack of Notty for a couple days. When that reaches high krausen pitch it into your stalled batch. That has more chance of resurrecting it than adding the dry or rehydrated yeast without first making it active.

Are you controlling or keeping the temps steady in any way?

There's a trick to determine what the lowest possible gravity for a brew is: Fast Ferment Test.

 

[Brewshna]

It's in a 19C room at the moment. don't have a fridge etc., so keep in cellar 17-18C, front room 19C or office 22C. that's all I've got. it's wrapped in a foil blanket to keep it dark.
So ill pop it back into the 22C room, give it a good shake to rouse the trub and make the ReStarter with Notty and DME and pitch at high krausen. The coco nibs have even been soaking in bourbon, ready to go in when fermentation is done. sucha shame.
Wish i knew what went wrong. I love imp stouts and want to brew many.

 

[Brewshna]

I brewed an IPA Last Sunday, 7.2ABV goal. pitched Nottingham, I think fermentation is already done, that's how I like it.

 

[IslandLizard]

give it a good shake to rouse the trub

Be careful not to aerate it, it will kill the beer. A gentle swirl (or stir) should do it. If it's in glass, be very careful, and don't put it on it's edge on a hard surface.

What kind of fermenter are you using?
If it's in a bucket don't remove the lid unless you have CO2 to purge the headspace thoroughly, afterward. Oxygen (air) is the nemesis of beer after fermentation has started or has finished.

This beer has not been transferred to a secondary, has it?

In many cases it's best to take the easier route instead of tinkering with it: Let it be for another week or 2, and then drink and enjoy the sweeter beer. Or maybe mix with another dryer one.

 

[IslandLizard]

There's also a need to oxygenate (or at least thoroughly aerate) higher gravity wort/beer when pitching yeast. In some cases even a 2nd time, 12-18 hours later, but before active fermentation has started. Once (active) fermentation has started, no.more.oxygen (or air)!

 

[Brewshna]

There's also a need to oxygenate (or at least thoroughly aerate) higher gravity wort/beer when pitching yeast. In some cases even a 2nd time, 12-18 hours later, but before active fermentation has started. Once (active) fermentation has started, no.more.oxygen (or air)!

it's in a 30l Speidel plastic fermenter with an airlock. primary of course
We pitched, made pizza and checked on it about 3h later and bubbles had started. We had loads of flour and bits in the wort, so we filtered through a nano mesh while transfer to fermenter, think that aerates it quite nicely.

 

[Brewshna]

Just in between, thank you so much for your help, it's really appreciated.

 

[dmtaylor]

Your recipe calls out 500 g lactose twice. Did you actually use 1 kg lactose? Each 500 g will add about 2,5 P to both the pre- and post-fermentation measurements, since this is an unfermentable sugar. IF you used 1000 g, that would have a significant impact on the recipe.

 

[Brewshna]

No has 500g in it. Jeah increases both OG and FG.