4th Stuck Fermentation

[brewbear]

Well this is frustrating, but I'm clearly doing something wrong. Of the last 5 AG brews, 3 have stuck during fermentation and not reached expected FG (way off). I'd like to ask advice on what might be underlying issue, and what to do on the current brew.

All brews have been 21-23L. All brews have been in the region of 1050-1060 OG, and for stuck fermentations, fermentation has been rapid over first 3-4 days but has plateaued soon after that. Stuck fermentations have been left in FV for at least three weeks, with 'swirling' to try to rouse yeast once it got stuck. I made the mistake of bottling two stuck brews as I couldn't get them re-started, but this resulted in bottle bombs. :sad: I want to avoid bottle bombs with my current stuck fermentation!

First question: what's causing the issue?
My thoughts and theories are here: what would people say is the most likely issue/ thing to change for next brew:

1. Fermentation Temp variation. I don't think it's this: On previous brews I thought it might be fermentation temp causing stuck fermentations (FV was in a room with varying temp). I've since built a brew fridge, and current (stuck) fermentation has been temp controlled.
2. Fermentation Temp too cold. On current brew (temp controlled in brewfridge) I mistakenly began fermentation on current brew at 15.5*c, and after three days rose to 17*c. It's currently set at 19.3*c. The yeast is Safale-US05, which suggests temp range of 15-22*c.
3. Wort aeration. Thinking back, fermentations started sticking after I began using a pump to move wort through the cooler. Before that, the drop of the wort as it dribbled in to the FV created loads of foam and presumably oxygenated the wort very well. Now I use the pump, the wort is delivered more smoothly/ causes less aeration, and so perhaps could be under-oxygenating. [I haven't aerated in any way]
4. Yeast pitching temp: I don't think it's this. Yeast has been pitched at 17-21*c consistently for all brews.
5. Yeast pitching preparation: I took the dried yeast (Safale US-05) packet's instructions on their word and merely sprinkled in to the FV. I've done this on most AG brews and never had a problem, but perhaps I should have made a starter? Brewlength is always 21L-23L.

Are one of the ideas above the likely cause/ issue? Want to make plans for next brewday to ensure no problem.


Second question: what to do about the current brew?
It's 22L milk stout has a FG target of 1022. Gravity readings and temps have been:

• Day 0 = 1064 OG at 15.5*c. Safale US-05 pitched by sprinkling directly in to FV.
• Day 3 raised to 17*c
• Day 5 = 1050 raised to 19.5*c
• Day 7 = 1041. Swirled to rouse yeast.
• Day 11 = 1040
• Day 17 = 1040

Should I:

1. Pitch more yeast (I have a pack of Safale US-05 in stock)? If so, sprinkle or starter or...?
2. Sterilise a stainless steel whisk and aerate?
3. Yeast nutrient of some sort? (Never used - any suggestions?)
4. Something else.

The beer has a gorgoues taste (although too sweet still) and I don't want to lose it, or create bottle bombs like I did with the other stuck fermentations!


Apologies for hugely long post. Suggestions very gratefully received! :pray:

 

[Redron]

Unlucky and quite frustrating I should imagine.
I posted a similar question last week (take a look at '1st AG stuck' ).

Received wisdom suggested a lack of aeration of the wort (I forgot!). I was apprehensive about aerating a semi fermented brew but apparently it is not an issue, only with fully fermented brews.

My solution was to add 1.5L of a newly brewed wort, vigorously aerated and a little more yeast. This really kicked my stuck brew (1022) into action for a day or so with a huge krausen within an hour ! I thought I had cured it but even now it is only at 1020 but still chugging away slowly, so I will leave it.

I would be tempted to give it some lash with a kitchen whisk or similar and get some O2 into it.

 

[MyQul]

I would think it's probably lack of aeration. You've used plenty of yeast which has been re-hydrated which I usually the other reason for stuck brews.

Unless you use pure oxygen and a stone, HBers cannot aerate wort to the idea ppm. So if your not aerating as well a you can (and by your description of your pump and cooler you may well not be) stuck brews may well result.

Stuck brews can be extremely hard to get down to terminal gravity once stuck. Maybe have a go at Redrons solution. Amylase enzyme can also sometimes unstick a brew but it's not always guarenteed

In your future brews I would suggest you take out 4L or so and put it in a 5L water bottle and shake the hell out of it then return the wort to the main boddy. This always works well for me (although I do it with the dilution water rather than wort, as I make a concentrated wort then dilute down into the FV). My brews always start after about 9-10 hours and never stick

Also have a look here for stuck fermentation tips

http://www.thehomebrewforum.co.uk/showthread.php?t=54457

 

[Twostage]

I'm also in the under-aerated camp (help, I can't breathe ). Further evidence is in your bottle bombs (or was). During bottling the beer gets aerated no matter how careful we do it. See the bottom of page two in the below - 'results' where it talks about the water getting 43% saturated with O2 just by letting the water flow into the fermenter.

http://www.brewangels.com/Beerformation/AerationMethods.pdf

This aeration will have re-started fermentation in your bottle bombs not the addition of priming sugar as there was plenty of fermentables already.

I'm sure I've read somewhere that it is difficult to aerate high gravity beers enough without using pure O2. A method which is more common in the USA. Must be possible though unless the monks knew something we don't.

 

[MyQul]

I'm sure I've read somewhere that it is difficult to aerate high gravity beers enough without using pure O2. A method which is more common in the USA. Must be possible though unless the monks knew something we don't.

I think the technique is to do a double aeration (and the one the monks may have used unless they managed to somehow bottle liquid oxygen and now all the records are lost) . Aerate as normal then aerate again 24 hours later

 

[rodabod]

Second question: what to do about the current brew?
It's 22L milk stout has a FG target of 1022. Gravity readings and temps have been:

• Day 0 = 1064 OG at 15.5*c. Safale US-05 pitched by sprinkling directly in to FV.
• Day 3 raised to 17*c
• Day 5 = 1050 raised to 19.5*c
• Day 7 = 1041. Swirled to rouse yeast.
• Day 11 = 1040
• Day 17 = 1040

That's a slow fermentation, even starting at 15.5C. Start by making sure your wort is well aerated (I use by pump via chiller to splash the wort, but there are many ways to froth it up as you know), and rehydrate your yeast for 30 mins or more in tepid water (mid 20's).

 

[brewbear]

Many thanks for the suggestions: much appreciated. Thinking I might sterilise a 5l bottle, take 3l of wort from FV tap, shake like a nutcase, and return to FV today. Plus get to LHBS to get Redrobs/amylase on Monday. Fingers crossed. Will report back.
Much appreciated [emoji3]