Possible Stuck Fermentation???

[kenmcchord]

Hey Everybody,
I've got a question about my current fermentation, specifically if it's possibly stuck or if my FG expectation is incorrect. Just a quick background, I started brewing around 2013 and I've had some luck brewing but this is the first time a fermentation seemed to stall for me. And to be clear, I'm feeling more and more like I really don't know what I'm doing short of follow recipes. So I'm seeking a little help troubleshooting.

I'm brewing the Gambler IIPA that I found in the recipes section. I plugged this into my Beersmith 3, then upscaled it to a 6 gal batch. Only hop I couldn't get was the Apollo, which I subbed out for Columbus instead but everything else is just as the recipe was posted. I started using Bru'N water for the water additions and I mashed with 2.5ml lactic which got me just short of 5.4pH. Here's the upgraded grain profile,
13 lbs 4oz Golden Promise
2 lbs 7 oz Flaked Wheat
I mashed in 20.30 quarts at 158° for a 75 min mash step of 147°, mash out 12 1/2 quarts of 205° for a 168° step. Fly sparged 2.5 gals at 168°. All went what appears to be well, hit my temps almost perfectly. The pre-boil gravity in Beersmith shows 1.052 but I only measured 1.040. I will say that my last few batches I came much closer to my expected pre-boil gravities. (I'm using a monster mill and that works quite well)

The recipe called for a 75 min boil and an addition of 1lb 8oz of sugar in the last 10 mins. My OG expectation was 1.076, I came in at 1.084; again I'm not sure why I would have been high given that I was low at the pre-boil.

The yeast is WLP066 London Fog ale, which I made a 1.6L starter of 1.036. I pitched the yeast at roughly 68° and had activity within 8 hours. By day three activity dropped off considerably, however there was bubbling. I cracked open the fermenter and dry hopped, installed a cold crash guardian and away it bubbled. It's now day 13 and the blow-off tube has virtually zero activity in the last couple of days. I took a sample yesterday and the gravity was 1.023, well above both the posted recipe FG expectation of 1.011, or that of my Beersmith FG expectation of 1.008. It smells exquisite and tasted nice, but that number seems higher.

Whew, that was a lot, but in reading many of these posts I knew this was important information. Is my FG expectation way off? Does 1.023 seem too high? Or is it possible that the wort OG was so high that I should have had a two step starter, giving the yeast a better chance of finishing it off? I have a package of safale US-05 sitting in my fridge that I could pitch in there to help finish it off, but the sample I pulled yesterday was nice and hazy and I'd hate to have that clear up.

Any help would be much appreciated, thanks in advance!

 

[Gnomebrewer]

The recipe called for a 75 min boil and an addition of 1lb 8oz of sugar in the last 10 mins. My OG expectation was 1.076, I came in at 1.084; again I'm not sure why I would have been high given that I was low at the pre-boil.

I suspect that you had some sugar stratification. Adding sugar (or LME or DME etc) late in the boil often ends up with imperfect mixing. Your preboil gravity was 1.040. If you boil off 20% that gives a gravity of around 1.050. Adding 1.5lbs of sugar gives 69 points of gravity, 69 points over 6 gallon is 11.5 points per gallon. So your OG would be somewhere around 1.062. Unless your boiloff is ridiculously high, you couldn't get to 1.084.

I took a sample yesterday and the gravity was 1.023, well above both the posted recipe FG expectation of 1.011, or that of my Beersmith FG expectation of 1.008. It smells exquisite and tasted nice, but that number seems higher.

That starter seems reasonable to me, as long as you oxygenated the wort well enough. First check, are you using a hydrometer or refractometer to measure gravity? A refractometer reading needs a correction made when alcohol is present. Second check, are you de-carbonating the sample before measuring gravity? Bubbles will push the hydrometer higher giving a false high gravity reading.

 

[kenmcchord]

I suspect that you had some sugar stratification. Adding sugar (or LME or DME etc) late in the boil often ends up with imperfect mixing. Your preboil gravity was 1.040. If you boil off 20% that gives a gravity of around 1.050. Adding 1.5lbs of sugar gives 69 points of gravity, 69 points over 6 gallon is 11.5 points per gallon. So your OG would be somewhere around 1.062. Unless your boiloff is ridiculously high, you couldn't get to 1.084.



That starter seems reasonable to me, as long as you oxygenated the wort well enough. First check, are you using a hydrometer or refractometer to measure gravity? A refractometer reading needs a correction made when alcohol is present. Second check, are you de-carbonating the sample before measuring gravity? Bubbles will push the hydrometer higher giving a false high gravity reading.

Thanks for the reply!

I have an oxygen wand on a bottle, adding roughly 2 mins of O2 on the 1 setting on the Blichmann O2 regulator (sorry, should have added this part). I don't have any idea of what my boil off rate is, I need to verify that at some point.

I'm using a hydrometer which I have calibrated through the use of distilled water and a 1.036 starter measured out with a precise scale. I don't know what de-carbonating the sample means, rather better said I don't know how to de-carbonate a sample. With regard to the stratification issue, I did mix it quite well and had a nice vigorous boil all the way to the end, along with a 30 minute whirlpool at 180°. I feel like I need to get a refractometer, and I need to get my sampling and gravity readings technique under control.

So assuming the 1.023 is an accurate reading, does this seem high to you? I have to say I am so confused as to what I should expect as a FG.

 

[Gnomebrewer]

I don't know what de-carbonating the sample means, rather better said I don't know how to de-carbonate a sample.

During fermentation, yeast produce a lot of CO2. Some of that CO2 dissolves in the beer, so it actually as a light 'fizz' to it. The longer you leave it after fermentation finishes, the more of the dissolved CO2 escapes. During an vigorous ferment, beer can actually tasted semi-carbonated. If the sample you use has bubbles rising (CO2 escaping), these bubbles stick to the side of the hydrometer and make it sit higher, which gives a 'false' high gravity reading. Try leaving a sample of beer out for a few hours (lets the CO2 escape) then measure gravity. Alternatively, pour a sample backwards and forwards between two vessels several times to agitate, then leave it for 10 minutes or so for the CO2 to escape. If you can see bubbles clinging to the hydrometer, you need to remove more CO2. Also, try giving the hydrometer a spin as it goes into the beer - it helps knock the bubbles off the sides of it.

So assuming the 1.023 is an accurate reading, does this seem high to you?

Yes. Especially given the low mash temp and sugar content. But I suspect it's an erroneous reading.

 

[kenmcchord]

During fermentation, yeast produce a lot of CO2. Some of that CO2 dissolves in the beer, so it actually as a light 'fizz' to it. The longer you leave it after fermentation finishes, the more of the dissolved CO2 escapes. During an vigorous ferment, beer can actually tasted semi-carbonated. If the sample you use has bubbles rising (CO2 escaping), these bubbles stick to the side of the hydrometer and make it sit higher, which gives a 'false' high gravity reading. Try leaving a sample of beer out for a few hours (lets the CO2 escape) then measure gravity. Alternatively, pour a sample backwards and forwards between two vessels several times to agitate, then leave it for 10 minutes or so for the CO2 to escape. If you can see bubbles clinging to the hydrometer, you need to remove more CO2. Also, try giving the hydrometer a spin as it goes into the beer - it helps knock the bubbles off the sides of it.



Yes. Especially given the low mash temp and sugar content. But I suspect it's an erroneous reading.

I do spin the hydrometer when I check it, but yeah it definitely had bubbles clinging to it. I will be checking it again tomorrow, and I will be sure to let it sit a while before I test it.

Also the last part, another part I forgot to mention, I've gotten to where I ramp the temps up towards the end of fermentation. I'm using a Penguin glycol chiller in conjunction with the Ssbrewtech fermenter buckets with pump and controller. Right now I have it set at 71° and actually have a radiating heater pointed at the fermenter as "winter has finally arrived in FL". I'll probably ramp that up one more degree, I had a diacetyl issue once before and I don't want to have that happen again.

 

[kenmcchord]

I pulled another sample yesterday and allow the sample to de-carbonate for a few hours. I still sampled the same, yesterday looked like 1.022. Additionally the increased temp of a degree or two didn't really cause the fermentation to kick back into gear. I did see a few bubbles, but I suspect that's just a result of CO2 coming out of solution as the temp increased.

So I am all but certain that my fermentation is stuck, and I am guessing that 1.022 is probably too high and there are still fermentable sugars that should be consumed. The question I have is should I pitch some safale us-05 to help finish out the fermentation, or maybe get another package of the WLP066 to keep the haze that is in suspension? Anyone?

 

[kenmcchord]

Checking the attenuation of the London Fog ale yeast expectation is 75-82%. I've never worked out what my FG expectation should be, just went off what was in Beersmith. I searched out calculating attenuation in the forums, seems the formula is simply the (OG-FG)/OG, which in this case, based on my current FG reading of 1.022 and my OG of 1.084, looks like I'm sitting right at 73%, just shy of the bottom of the attenuation expectation from White Labs. But a far cry from the 1.008 expected FG that Beersmith predicted. (84-22=62/84=73%)

So... just to type what I think I figured out.
Beersmith expectations were 1.076 OG and 1.008 FG, which based on the formula above, would have yielded an 89% attenuation, which is well above the attenuation expectation that White Labs lists for this strain of yeast. Even checking the recipe that was posted here the OP was getting just shy of 85% apparent attenuation (1.073OG/1.011FG), a solid three points above the attenuation estimates on the White Labs site. Am I on track regarding attenuation? Why would Beersmith put the expected FG at 1.008? Clearly there is a lot more for me to learn in that program.

Maybe this fermentation is truly finished. Today is day 14 and there's not been much in the way of activity for a while. Think I'll cold crash it tomorrow and keg it up on Friday.

 

[Gnomebrewer]

The listed attenuation is a guideline for all-malt wort. You mashed low and included a fair hit of simple sugar, so you should see a lot higher attenuation than what is listed for the yeast. It's very complex though - there are so many things that can affect attenuation that expected FG is only ever a rough guide. The only way to get a better estimation is to brew the same beer multiple times.