Short on the FG

[Amy Kemp]

I started a coffee stout on 11-17, pitched yeast on 11/18.

Per the recipe OG 1.069/FG 1.008
2 packs of Safale US 05

Fermentation temperature 64 degrees (basement doesn’t get any warmer).

My OG WAS 1.072 and I’m almost 4 weeks now and my FG is 1.024.

Trying to trouble shoot my short ferment to improve next time. Any suggestion?

 

[grampamark]

Is your FG stable, or is that a single reading?

Extract or all grain? If all grain, mash time and temp will have an effect on how much of the sugar is fermentable, as will the grain bill. Giving us the recipe and your process would help.

Your potential alcohol, at 100% attenuation, would be a little over 9%. Your at 6.3% ABV now, which is about 63% attenuation. The recipe numbers would require almost 90% attenuation, which is pretty high for -05. That yeast is a pretty reliable 70-75%.

You didn't mention the batch size. Two packs of yeast should be enough for up to 10 gallons unless the yeast was well past it's due date. With the amount of fermentables suggested by the OG, you should expect an FG of at least .015, maybe a bit lower.

 

[Amy Kemp]

Attached is the recipe sheet from my local home brew store. 5 gallon all grain. Pre milled unsure of mill size.

I use a two vessel batch sparse. Mash in a 10 gallon Igloo with false bottom. Mashed at 152 and at the 60 min mark it was down to 149. Strike water at 172 degree.

Immersion chilled the wort down to 110, transferred to carboy, into the fermentation tank over night to drop the temp to 64, then pitched the yeast and held the temp at 64 since. Yeast was pitched 11/17.

I check the SG 10 days ago it was 1.026.

 

[grampamark]

Your mash conversion was pretty good, based on the OG, so the grain crush was probably not an issue, nor were your mash and sparge temps.

I'm inclined to think the yeast just didn't perform. Possibly insufficient oxygenation at pitching or outdated yeast with low activity.

 

[TechFanMD]

Just to check....what did you measure FG with?

It sounds to me like your mash was higher in temp than you think. How/where in the mash (depth) did you measure temp? US-05 doesn't normally stall like that.....and that packet would have to have been really old to have that much effect....nevermind two packs.....it's hearty and predictable.

That's about 17lbs of grain. I don't know your process and equipment, but for instance - if I hit 17lbs of grain with 1.25quart/lb mash thickness to be about 5 1/4 gallons with 172 degree water in my preheated mash tun, my mash would be 158F. Like I said....your equipment is different, I'm just saying that a high mash temp is going to equal fewer fermentable sugars and a higher FG.....which matches what you're seeing.

Is it possible you measured near the top or a cool spot and miscalculated strike water temp?

I'm not saying oxygenation isn't possible as an issue - but for a dry yeast like 05 you would have to have gone out of your way to have it be too low in oxygen for it to just stall out that high. I think it still would have gotten down to 1.015 or so by now.

Look at it this way.....a low attenuating yeast is not an uncommon choice for a beer style like this (something like Windsor) so it'll probably be very tasty.

 

[kh54s10]

I would say for that recipe the 1.026 might be a touch high, but 1.015 would be unlikely. It is a stout after all.....

 

[Abbas]

I made 2 Imperial Stouts recently, both with US-05. My strike temps were high (one at 172 and one at 174). I use an Igloo for my mash tun, but did a 90 minute mash and boil for these beers. I do not preheat my mash tun, so this is possibly why I don't run into issues? I don't do much to aerate before pitching, besides running my wort through a stainless steel mesh strainer. My closet that I ferment in stays at an ambient temp between 67-69. Both of my stouts attenuated at 79%.

I would guess either your yeast was no good or perhaps your basement was colder than you thought. It would be doubtful that aeration would be the issue. I use this yeast frequently and it attenuates well for me. It's difficult to tell what your issue was. I have a Coffee Milk Stout fermenting with US-05 currently. I believe my strike temp was 172ish as well. I will let you know what happens with this batch.

 

[Amy Kemp]

Bringing up the topic of oxygenation reminds me I didn’t even airate/agitate the wort before yeast pitch.

I know my temperature was accurate as I log daily digital temperature from my basement. My temperature probe for measuring mash temp however is only 6” long.

 

[Abbas]

Bringing up the topic of oxygenation reminds me I didn’t even airate/agitate the wort before yeast pitch.

I know my temperature was accurate as I log daily digital temperature from my basement. My temperature probe for measuring mash temp however is only 6” long.

I think homebrewers oxygenating wort prior to pitching isn't as necessary as a lot of people think. I may be in the minority here, but I think during a typical brewing process your wort is being exposed to plenty of oxygen. When you're transferring from your kettle to fermenter I imagine you're introducing you wort to enough oxygen. I realize that yeast needs oxygen to do it's thing, but unless you're using some sort of sealed system where your beer never has contact with the ambient air I think you'll be fine.

I would by no means say I'm a fermentation expert so you can take views with a grain of salt. I'm soon moving to 10 gallon brewing and would love to do an experiment aerating one half of the wort and not the other.

 

[Amy Kemp]

I made 2 Imperial Stouts recently, both with US-05. My strike temps were high (one at 172 and one at 174). I use an Igloo for my mash tun, but did a 90 minute mash and boil for these beers. I do not preheat my mash tun, so this is possibly why I don't run into issues? I don't do much to aerate before pitching, besides running my wort through a stainless steel mesh strainer. My closet that I ferment in stays at an ambient temp between 67-69. Both of my stouts attenuated at 79%.

I would guess either your yeast was no good or perhaps your basement was colder than you thought. It would be doubtful that aeration would be the issue. I use this yeast frequently and it attenuates well for me. It's difficult to tell what your issue was. I have a Coffee Milk Stout fermenting with US-05 currently. I believe my strike temp was 172ish as well. I will let you know what happens with this batch.

What was your mash temp then? Or are you using mash and strike interchangeably?

 

[Abbas]

I'm working with old equipment that my friend provided. We typically brew together, but his mash tun does not a thermometer port. I could not tell you what the actual mash temp was. I brewed one individually, and temped it after the 90 minute mash, but I forgot to document it... The only thing I know is that my strike water was at 174. Sorry I can't be of more help here.

 

[DVCNick]

FWIW my last batch with US-05, I completely forgot to aerate and got attenuation over 82%.

Just parroting what I've read here, I've seen many people say that dry yeast contains everything the yeast needs in terms of nutrients and oxygen, and adding those things separately is not nearly as important as it is with liquid yeast. I don't know if that is true in all cases, but it aligns with my limited experience so far.

 

[CascadesBrewer]

Mashed at 152

One tip I would have would be to calibrate your thermometer. I have a "decent" dial thermometer, but after a while it got to the point where it was off about 5 degrees at mash temps. I tried calibrating mine at freezing and boiling point, but it seemed like assuming my a decent lab thermometer (fairly cheap...like $10) was accurate was my best approach.

 

[rabbitburger]

Did you check the expiry date on the yeast packets? Did you rehydrate the yeast before pitching?

 

[RPh_Guy]

Standard advice for a "stuck" fermentation:
1. Warm it up 5-10F, and
2. Swirl to rouse the yeast.

 

[Amy Kemp]

Did you check the expiry date on the yeast packets? Did you rehydrate the yeast before pitching?

I did not. But will keep that in mind moving forward

 

[Abbas]

This just happened to me too now. My bet is that my strike water was to hot for the amount of grain I had in this and the mash ended up too hot. My OG was 1.060 and I'm only down to 1.027. I added nutrients and pitch another packet of yeast tonight, but I assume all that's left are unfermentable sugars. If nothing else at least I'll have a nice and sweet coffee milk stout. With my 2 Imperials I made, I had about double the grain bill so my higher strike temps were probably not as big of a deal.
I'll report back in a few days.

 

[mulletmaster]

Immersion chilled the wort down to 110, transferred to carboy, into the fermentation tank over night to drop the temp to 64, then pitched the yeast and held the temp at 64 since.

Unrelated to your question i would use caution with this chilling approach depending on your carboy material. Regular glass does not tolerate thermal shock well and either adding warm wort or placing a warm carboy in a freezer could cause it to break.

 

[Amy Kemp]

Unrelated to your question i would use caution with this chilling approach depending on your carboy material. Regular glass does not tolerate thermal shock well and either adding warm wort or placing a warm carboy in a freezer could cause it to break.

Freezer was at room temp when I added the carboy. Valid point however and duly noted. Now that I think about it, I think I started that in a plastic bucket.

 

[Amy Kemp]

This just happened to me too now. My bet is that my strike water was to hot for the amount of grain I had in this and the mash ended up too hot. My OG was 1.060 and I'm only down to 1.027. I added nutrients and pitch another packet of yeast tonight, but I assume all that's left are unfermentable sugars. If nothing else at least I'll have a nice and sweet coffee milk stout. With my 2 Imperials I made, I had about double the grain bill so my higher strike temps were probably not as big of a deal.
I'll report back in a few days.

It’s definitely on the sweeter side. Not overwhelming like others I have had. Very drinkable. Much more coffee flavor than I wanted, but I do love coffee

 

[Amy Kemp]

Standard advice for a "stuck" fermentation:
1. Warm it up 5-10F, and
2. Swirl to rouse the yeast.

What are you using to warm it up. My basement doesn’t get much over 65-67 and I’d rather not have to shuffle stuff upstairs.

 

[Gnomebrewer]

My OG was 1.060 and I'm only down to 1.027

What did you measure gravity with? Hydrometer, or refractometer?

(The same question was missed by the OP as well when asked previously).

 

[RPh_Guy]

What are you using to warm it up. My basement doesn’t get much over 65-67 and I’d rather not have to shuffle stuff upstairs.

Lots of options:
A temperature controller (I use a dual stage inkbird 308S) attached to a heat source -- Fermwrap, heating belt, seedling heat mat, space heater, ceramic heating bulb, an incandescent bulb in a coffee can, etc.

Cheers

 

[Abbas]

What did you measure gravity with? Hydrometer, or refractometer?

(The same question was missed by the OP as well when asked previously).

Hydrometer. Why do you ask?

 

[Gnomebrewer]

Hydrometer. Why do you ask?

If a refractometer is used, the ethanol present in the fermented (or fermenting) beer distorts the reading, which requires a calculation to correct it. Gravities measured with a refractometer after fermentation start read higher than the true gravity. The most common problem with brewers reporting a high FG is that they've used a refractometer - the FG is actually where it should be.

 

[Amy Kemp]

If a refractometer is used, the ethanol present in the fermented (or fermenting) beer distorts the reading, which requires a calculation to correct it. Gravities measured with a refractometer after fermentation start read higher than the true gravity. The most common problem with brewers reporting a high FG is that they've used a refractometer - the FG is actually where it should be.

I used a hydrometer and corrected it for temperature.

 

[Amy Kemp]

Lots of excellent dialogue her crew. Truely appreciate all of the content.

 

[deadwolfbones]

As someone else said, I'd raise temp and swirl to rouse yeast. They might kick off again.

 

[bracconiere]

i'd add there's always glucoamylase you can add! it'll go to 1.000 then!

 

[Abilor]

This has happened to my so many times it's why I now use an Oxygen wand. Those red tanks are $10 at any Home Despot or Blowes. My ferments all now need a blow-off tube they're so vigorous after priming it with the O2 wand for 60 seconds and using a fresh starter...

 

[bracconiere]

This has happened to my so many times it's why I now use an Oxygen wand. Those red tanks are $10 at any Home Despot or Blowes. My ferments all now need a blow-off tube they're so vigorous after priming it with the O2 wand for 60 seconds and using a fresh starter...

they ferment out faster too? not trying to hijack, just quick question. i use gluco, and get 1.000 every time, but wouldn't mind speeding it up.

 

[Abilor]

they ferment out faster too? not trying to hijack, just quick question. i use gluco, and get 1.000 every time, but wouldn't mind speeding it up.

Oh definitely. The metabolic activity is night and day over when I would just splash and swirl, and then pitch a smack pack without a starter. I can't use those little airlocks if I use a starter and the O2 wand. Within 3 hours it's bubbling away, and within 24, there's krausen shooting through the blowoff tube into a 2 quart container filled with StarSan water. Primary ferment is done within 48 - 72 hours of initial pitch, meaning less than one air bubble every 60 seconds. I still PF for 7 days, and SF for another 7. I like to SF since it gives me a chance to filter out some trub and protein haze, etc. And I get my PF vessel back.

But yeah. I'll never go back to not using the O2 wand. Amazing. I got mine at an online HBS.

 

[bracconiere]

Oh definitely. The metabolic activity is night and day over when I would just splash and swirl, and then pitch a smack pack without a starter. I can't use those little airlocks if I use a starter and the O2 wand. Within 3 hours it's bubbling away, and within 24, there's krausen shooting through the blowoff tube into a 2 quart container filled with StarSan water. Primary ferment is done within 48 - 72 hours of initial pitch, meaning less than one air bubble every 60 seconds. I still PF for 7 days, and SF for another 7. I like to SF since it gives me a chance to filter out some trub and protein haze, etc. And I get my PF vessel back.

But yeah. I'll never go back to not using the O2 wand. Amazing. I got mine at an online HBS.

Thanks, i think i'll try it, already have the red o2 battles for my mini welding stick....

(and apparently my trolling caught a fish, Welcome!)

 

[Northern_Brewer]

I wouldn't sweat it, your S-05 may not have performed quite as intended but you're right on target for a British stout at least - eg the post-WWII Bass imperial stouts typically started around 1.077 and ended at 1.025-27 (64-67% attenuation), at a time when their yeast was attenuating 78-81% in their paler beers. You'll never get as much attenuation in dark beers, and all yeast start to struggle a bit over 1.060.

And don't worry too much about oxygen - whilst it won't particularly hurt, it's far less important for dry yeast as mentioned above. For this kind of beer yeast nutrition is far more important. It's also worth checking pH when mashing anything with significant amounts of dark grains.