High FG - next move?

[Gaucho Wino]

Hi All - I recently brewed a Coffee Milk Stout with an OG of 1.067 (11.5 lb grain bill, 1 oz 60 min hops, 1 lb lactose at 15 min, 4 oz coffee ground at flame out). Fermentation was temperature controlled at 66 degrees and I left it in primary for 20 days. All seemed well, but then I did a rookie move today and put it in a keg without checking the FG before hand, just assuming ~3 weeks was enough time to complete fermentation (bubbles the first week and then nothing the last two weeks). I measured the FG after putting it in the keg and it was 1.038, which calculates to 3.8%. Now I'm wondering what my best next move. is..one idea I had was to add another yeast packet directly to the keg and let it ferment in the keg with the hope of finishing the job. Good idea, bad idea, better options? Thanks in advance for any advice.

 

[Camelot Legends]

Are you using a refractometer of a hydrometer?

 

[Gaucho Wino]

I measured using both...the hydrometer was 1.38, the refractometer was a bit blurry, but looked to be in a similar range.

Edit: temp was around 66 at measurement.

 

[Camelot Legends]

As far as I know, refractometer doesn’t work with alcohol in solution. Don’t use for FG.

How was your mash temp?

 

[Gaucho Wino]

Mash temp was ~156 and held fairly well...maybe lost a few degrees over 60 min, but I don't recall seeing any type of significant drop off.

Edit: In terms of diagnosing where the culprit lies, I had my Imperial Yeast A01 packet for maybe 6 weeks before I brewed...I'm guessing that was the issue?

 

[VikeMan]

What was the breakdown of the grain bill? Yeast strain?

 

[Gaucho Wino]

What was the breakdown of the grain bill? Yeast strain?

- 5 lbs American 2-row
- 5 lbs Maris Otter
- 0.5 lbs Dehusked Carafa II
- 0.5 lbs English Dark Crystal
- 0.25 lbs English Black Malt
- 0.25 lbs English Chocolate Malt
Imperial A01 (maybe brewed 6 weeks after I purchased it)

 

[VikeMan]

With those malt proportions, mash temp, and mash length, plus 1 lb of lactose, an OG of 1.067, and A01, I'd expect an FG somewhere around 1.025. So, a couple questions...

- Unless you were adjusting the FG refractometer reading with a refractometer calculator, it couldn't have been the same (or even close) to the hydrometer reading. How sure are you of the 1.038 hydrometer reading?

- A mash temp of 156F is going to influence the wort toward being not very fermentable (already accounted for in my estimate of 1.025). How confident are you about your thermometer and the 156F? A few degrees higher would make the wort even less fermentable.

 

[Gaucho Wino]

With those malt proportions, mash temp, and mash length, plus 1 lb of lactose, an OG of 1.067, and A01, I'd expect an FG somewhere around 1.025. So, a couple questions...

- Unless you were adjusting the FG refractometer reading with a refractometer calculator, it couldn't have been the same (or even close) to the hydrometer reading. How sure are you of the 1.038 hydrometer reading?

- A mash temp of 156F is going to influence the wort toward being not very fermentable (already accounted for in my estimate of 1.025). How confident are you about your thermometer and the 156F? A few degrees higher would make the wort even less fermentable.

Good questions, and I have to admit, at this point, I'm "sure" of less and less, here is what I think...

I feel pretty good about the hydrometer reading in terms of reporting what it showed. Since I already racked the beer into the keg, I used the remaining 1 inch of beer/trub to measure the FG. I know I had a lot of trub while measuring, but my understanding was that it wouldn't matter...? As far as the refractometer...like I said, it was kinda blurry and to be honest, I just looked at it as a curiosity and it was in the range of sub 1.4, but didn't try and pinpoint exactly as I did the hydrometer.

Regarding my confidence of the mash temp of 156...good point, I didn't take notes, but I have this sinking feeling that it may have been a few degrees higher...

 

[Camelot Legends]

Have you had issues with FG with other batches?

 

[VikeMan]

I feel pretty good about the hydrometer reading in terms of reporting what it showed. Since I already racked the beer into the keg, I used the remaining 1 inch of beer/trub to measure the FG. I know I had a lot of trub while measuring, but my understanding was that it wouldn't matter...?

It could matter, depending on how much (if at all) the trub impeded the hydrometer.

As far as the refractometer...like I said, it was kinda blurry and to be honest, I just looked at it as a curiosity and it was in the range of sub 1.4, but didn't try and pinpoint exactly as I did the hydrometer.

If the FG was really 1.038, I'd expect the (uncorrected) refractometer to indicate approx. 1.047. If the refractometer's (uncorrected) SG scale did indicate 1.038, that's would mean your true FG was likely around 1.021.

Regarding my confidence of the mash temp of 156...good point, I didn't take notes, but I have this sinking feeling that it may have been a few degrees higher...

You could eliminate or confirm a bad hydrometer reading as the culprit by taking a clean sample from the keg, degassing, and measuring. And you could test your mash thermometer with crushed ice water and with boiling water.

 

[Gaucho Wino]

Have you had issues with FG with other batches?

For the most part no...this was my 4th batch. 2 went correct, maybe my last one came out a little light...I thought I fixed that this time through a finer crush (BIAB).

 

[Gaucho Wino]

It could matter, depending on how much (if at all) the trub impeded the hydrometer.



If the FG was really 1.038, I'd expect the (uncorrected) refractometer to indicate approx. 1.047. If the refractometer's (uncorrected) SG scale did indicate 1.038, that's would mean your true FG was likely around 1.021.



You could eliminate or confirm a bad hydrometer reading as the culprit by taking a clean sample from the keg, degassing, and measuring. And you could test your mash thermometer with crushed ice water and with boiling water.

I’ll do a clean sample tomorrow and test the mash thermometer as well...thanks for all the feedback,

 

[Gaucho Wino]

Morning update: pulled a fresh sample out of the keg and hydrometer was 1.031, which calculates to 4.7%. I feel more confident in this reading without the trub floating around. The alc % is better, but short of what I was expecting.

After reflecting on it last night, I think my mash temp must have been too high. I remember getting the water up to around 168 (or so) and then thinking it was still a little high after the grain addition, but didn’t understand the significance of that at the time...

 

[Camelot Legends]

It’s also possible that it’s still fermenting. I would give it a week or two and pull another sample