High FG, not sure why

[LowNotes]

I brewed a clone of the Bell's Two Hearted ale, based on this recipe:

https://www.homebrewtalk.com/f69/bells-two-hearted-ale-clone-close-they-come-91488/

Target OG = 1.064, Target FG = 1.010

This is my second batch of this clone. My first ended up with OG = 1.053/FG = 1.012. I figured my lower OG probably came from lower efficiency from BIAB, but the beer tasted really good, and was very close to the original Bell's in taste. I mashed at 155*.

On my second attempt, I decided to keep the grain bill identical, but mashed at 150* instead, and did a 75 minute boil instead of a 60, to try and boost the OG a bit. My OG was 1.060, which I felt pretty good about, as 7 gravity points is a nice little bump without adding any grains. The weird thing, is that when I bottled this batch this weekend, after 3 weeks in the fermenter, the FG was 1.019. This is a good bit higher than my original batch, and even worse, I was actually aiming for a LOWER FG by lowering the mash temps...

Any ideas on why this might be? It is possible my mash temps weren't measured as precisely as I thought, but I have used the same process for over 10 batches and this is the first really weird OG/FG number I've gotten. I am typically a little low on OG, but my FG's are almost always spot on. If it was the mash temps, what temp would cause such a high FG?

I pitched washed S-O5 that I had given a small starter the night before (1 oz DME/ 1 cup water), fermentation was fine as near as I could tell...

 

[RM-MN]

What was the fermentation temperature? Your yeast might have decided to take a nap instead of finishing the job if the temperature was too low or if it dropped during the fermentation period.

 

[ApothecaryBrewing]

Could be the fermentation just stalled. How did you aerate? I found my fermentations were holding up around 1.020 because I wasn't able to aerate enough. Got a Williams O2 kit and fixed that issue real fast.

Could also have been stressed yeast or fermentation temps were off. I would guess maybe aeration though.

 

[LowNotes]

Fermentation temps were pretty steady. I ferment in my house in the winter, the thermostat stays on 68*, which I know is a little on the high end, but I gotta keep SWMBO happy too, and she hates cold. I check the bucket thermometer every couple of days, and always at least once when fermentation is rolling along to make sure nothing crazy is happening, and it never went above 70*.

For aeration...I typically rely on the pour, i.e. I pour the entire contents of my brew kettle into my bucket, creating a good solid 1-2" of bubbles on the surface, plus whatever will dissolve I assume. I also will shake the fermenter for 1-3 minutes afterwards once I take a gravity reading and put the lid on. I have probably been shaking less and less as I have had no ill effects....until maybe now.

So follow-up question...if it was either of these 2 issues, will I likely have 22oz bottle bombs on my hands?

 

[ApothecaryBrewing]

Even with shaking the fermenter you aren't getting the ideal amount of dissolved oxygen into your wort. As per Chris White, of White Labs, shaking or using an aquarium pump with a filter attached will only get you to about 8ppm, which is the maximum you can achieve when utilizing atmospheric oxygen to aerate your wort.

Ideally your dissolved oxygen concentration should be up around 12-15 ppm which is only achievable by using pure o2 and an aeration kit.

That being said plenty of homebrewers find the shaking method works well enough for them, but no matter how much shakin' is going on, you will only max out at roughly 55-66% of the ideal amount of O2 you want for ideal yeast activity.

My guess is that you are probably hitting that max at around 8 ppm but some other part of your system is stressing your yeast so that it cannot ideally preform at those levels.

Do you use yeast nutrient? Are you pitching enough? There are several ways to stress your yeast into early retirement. I would start narrowing down your variables and see what works for you. For me, it was an o2 aeration kit from Williams. After using it, it was the first time, aside from a saison using monster belgian yeast, that I was able to get significantly below the 1.020 mark. For other people it might be temperatures or nutrients.

Another side note, I typically ferment around 68F as well, but fermentation will create heat and can raise the internal temperature of your brew. I have heard it can jump as much as 10F just from fermentation activity. I now tend to start my beers at 68-69F to let them pick up steam then I throw them in my basement for 5 days or so which is 60-62F, a little chilly but once fermentation is cranking, I count on the yeast producing some heat and keeping my beer around 65-67F.

As for bottle bombs... I have never had any. I prime the recommended amount for the style, although I typically hang on the low end. If an ale is supposed to be between 2-2.7 volumes of CO2 or whatever, I will prime for 2 if my FG is a little high. I have never had bombs but I have had incredibly over-carbonated beers... almost champagne like. If it is something you are worried about, prime at the low end and wait a little long for them to carb up.

OH OH OH... sorry to continue! But I was chatting with a fellow homebrewer who gave me a great idea. He says when he bottles, he will bottle 1 12-20oz. plastic soda bottle with primed beer. When the bottle becomes firm with carbonation, he cold crashes the whole lot to stop it. I thought that was pretty ingenious.

 

[LowNotes]

Thanks for all the helpful info!

I may have to look into an aeration kit as the next addition to my system. I liked the williams website, as it explained how the yeast use oxygen to strengthen cell walls, which is required for them to thrive in a higher ABV brew. Since I like stronger beers, and brew them often, this could be the ticket.

I always try and check on my brews at peak fermentation to make sure the temps don't get above about 71*, if I ever see one above that I will give it a cold bath to keep it in check. Hasn't ever been an issue to date. I have a fermentation chamber in an old fridge, but the garage is too cold for it to work in the winter...I am toying around with schems to use heat pads to provide heating,possibly rigging one to a timer and have it cycle on ever couple hours, but I am trying to avoid buying an expensive 2-stage controller.

With regards to the bottle bombs, I wasn't as much worried about the amount of priming sugar I use, as I typically just go with 4oz/5gallons and am not at the point yet where I am trying to get fancy with carbing to-style (one day though, I am gradually refining my process) as long as my beer is bubbly. I was more concerned if the fermentation becomes un-stuck with the addition of the priming sugar as I am assuming this would mean the yeast would eat not only the priming sugar, but would continue to ferment the original sugars to something below 1.019. I guess it probably isn't worth worrying about, I keep my bottles isolated in a big cardboard box just-in-case for 3 weeks after bottling, so if they blow it won't make too big of a mess.

Oh, you had also mentioned the amount of yeast pitched...I used some washed yeast form an older batch. I don't know exactly how much, but there was about 1" in the bottom of a 1-pt mason jar. From everything I have read, this is a pretty large quantity of yeast, which shouldn't even really require a starter. I always add 1oz DME and 1 cup water to the mason jar a couple days before to wake the yeast up and make sure they are still viable.

It sounds like it may be a perfect storm of slightly under-aerated, slightly over-temp, and some unknowns as far as yeast health/quantity/viability. Not great, but I am sure the beer will still be good, at least good enough for me at home