Stuck Stout - What to do next?

[vortura]

Hi all,

I had a go at brewing my first stout on Saturday, the fifth batch I've done in all, and the first time I've had what seems to be a stuck fermentation. I sprinkled a whole pack of Mangrove Jack M42 into 10L of wort at 16C/61F at 8PM on Saturday, and placed the fermenter inside my temperature controlled fridge, set to 19C/66F. OG was 1.048 measured with a hydrometer and the wort was aerated before pitching by giving the fermenter a good shake. I checked it at 3PM on Sunday, and the airlock was bubbling away nicely.

Sunday was fathers day here, and lucky me, the kids got me a Tilt hydrometer. Monday evening, I sanitised it, and dumped it in the wort, which came back with a reading of 1.020, so everything seemed to be well on track. Tuesday morning though, it was still sitting on 1.020, so I suspected the fermentation might have slowed up or stalled. The airlock had stopped bubbling at this point, but from the gunk on the walls of the fermenter, it seemed like there had been a reasonable amount of krausen at least. I bumped the temperature up to 21C/70F, gently swirled the fermenter hoping to agitate the yeast, and headed off to work

Tuesday evening, however, and it's still firmly stuck on 1.020. I wondered if it might be a problem with the Tilt, so I took a sample and checked it with the hydrometer, which showed more like 1.022 - a discrepancy, but not in the direction I was hoping. To be honest, the sample tastes great, so it's not a disaster by any stretch. 1.048 -> 1.022 is about 3.4% ABV, so that's okay, even if the body and bitterness might be a bit off.

What I'm wondering though is, what I can learn from this episode, and what to do next, if anything. I guess the obvious answer is to leave it and see what happens, but I was also considering the option of pitching more yeast. Is there any rush to do that, or could I leave it a week or so and then decide? I was planning on fermenting for about 14 days anyway.

The grain bill was:
63% Gladfield Pilsner
13% Gladfield Supernova
9% Gladfield Brown
7% Lactose Sugar
4% Gladfield Light Chocolate
3% Bairds Black
1% Gladfield Roast Barley

I was wondering about the possibility of unfermented sugars inflating the OG but limiting the FG. Is there anything in that grain bill to suggest this could have been a factor? I mashed at 68C/154F for 60 minutes, with a 75C/167F mash out for 10 minutes. I use a grainfather, so I think those temps should be reasonably accurate.

Any thoughts or advice would be appreciated.

Cheers!

 

[Qhrumphf]

Lactose is completely unfermentable by yeast (domesticated brewing yeasts at least, can't speak for wild yeasts) and you've got a pretty big portion of it.

 

[Gnomebrewer]

The lactose would be responsible for about 4 to 5 points of gravity (both OG and FG), but 1.022 is still higher than expected. I wouldn't trust the initial TILT reading. It has only been 3 days - lwarm it up, leave it for another three then take another gravity reading.

Oh, and I got a beer mug that says 'Worlds Okayest Dad' for fathers day, so you definitely got the better of that deal!

 

[vortura]

Thanks both, I didn't realise the lactose doesn't ferment out, so that's a few points there as you say. I guess I'll just wait it out in that case and see what I end up with. The Tilt seems cool, but I'm not sure it's a good fit for my slightly OCD nature. Whereas previously I probably wouldn't have taken a reading for at least 7 days, now I'm checking every 3 minute or so from the comfort of the sofa.

Thanks!

 

[Kickass]

I think I recall reading that folks needed to calibrate their Tilts? I don’t own one and I might be mistaken but might be worth looking into. Good luck!

 

[Jag75]

What was your projected numbers on the Gf app? 1.048 seems low to me . I would think a stout at 1.022 is good. I think mine finish around there maybe 24 -26 but my OG is 1.069.

Nice fathers day gift that was cool. Gnomebrewer your gift made me chuckle that is pretty funny.

 

[vortura]

I was expecting the OG to be slightly lower than that actually, about 1.046, and then estimating FG at maybe 1.010? From the comments about lactose above though, I guess that was never going to happen. Gravity still sitting on 1.020 (per the Tilt) this evening, so as a last ditch effort to get things moving again, I've given it a gentle stir with a sanitised spoon, and bumped the temperature to 22C, which is the top end of the range for the yeast. Otherwise I'll just leave it to sit for a week or two and get it bottled.

Thanks again everyone for the advice.

 

[myndflyte]

Have you taken a real gravity reading and compared it to the Tilt? They usually need some calibration, especially out of the package.

 

[vortura]

Yes, it was 1.022 by hydrometer reading as of yesterday. I’m not really expecting the Tilt to be 100% accurate, but mostly just as a ballpark indicator of fermentation activity. I will calibrate it properly after this batch however.

Cheers

 

[sleev-les]

I recently did a stout that had the same outcome. OG was 1.048 and the final was 1.020. I used Wyeast, but was thinking the yeast wasn't yielding the correct volume since it was 4 months old. I re-pitched dry and I got a little movement, but nothing to significant. In the end, the stout still tasted good and we are still drinking it. You just get to drink more at such a low ABV.