Higher than expected FG (1.041 vs 1.018)

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Belariad

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I'm brewing my first big Imperial Stout (1.100 OG) and after 4 weeks I still haven't achieved my desired FG. Here's my fermentables list:

15 lbs LME (light)
1 lb Chocolate
1 lb Roasted Barley
3/4 lbs Crystal 60L
3/4 lbs Crystal 120L

Brewers friend expected an OG of 1.940, and I got very close to that with 1.100. It calculated 1.018 FG but as mentioned in the title it's only achieved 1.041 after 4 weeks. I only steeped the specialty grains but I'm pretty sure that brewers friends calculator accounts for that.

I pitched almost 2 full packs of Safale US-05 and aerated very well (ran the entire wort through a nylon mesh bag) before pitching. I heard that under aeration for big beers can be a problem, but isn't oxygen only required for yeast to multiply? I thought it would still ferment until its target FG but possibly just slower right (with possibly flavour changes)? I read somewhere that warming it up and agitating the yeast back into solution might help? Or possibly re-pitching another pack of Safale US-05?

My apartment is usually around 68 degrees during the day, but sometimes at night it goes as low as 60. I'm still new to brewing and haven't figured out a temperature control system yet, but I could buy a heater for that room if you guys think it would help.

Any help would be appreciated, and let me know if I missed any important info.
 

Quaker

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With a similar Gravity RIS I brew annually, I pitch 2 packs of hydrated yeasts in 3 gallons (typically a 9-10 gallon batch split 3 ways with different yeasts) and oxygenate twice. I normally oxygenate right before pitching and again after 8-12 hours before active krausen is visible. You didn't say if you hydrated the yeast or not. But none of that helps you at this point on this batch.

Pitching another pack of yeast straight in probably won't help. if you make a starter and pitch it when fully active you may have a shot. I'd make a starter, and once active, double its size with an equal volume of the stalled beer. Wait 48 hours, then pitch it all in.

Warming up a bit and rousing may also help. Other wise you may be in for a long wait. You're at almost 60% apparent attenuation as is. I'd be surprised if you can get another 10 points out of it due to the alcohol already present which will be a challenge for new yeast.
 

doug293cz

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are you checking gravity with hydrometer or refractometer?
To the OP: The question is important because a refractometer is affected by alcohol in the beer once fermentation has started. You can't use the direct reading. You can use a calculator, like this one, to correct for the presence of alcohol. The corrected reading may not be as accurate as a hydrometer reading, but it is usually good enough.

Brew on :mug:
 

Calder

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I think you are done, and you had a bad OG measurement.

I assume this is 5 gallons.

15 lbs LME in 5 gallons will get you 1.108. Add 3.5 lbs of steeping grains and you are probably closer to 1.120. So you went from about 1.120 to 1.041.

The sugars from the grains are mostly unfermentable, so if I take them out just to figure out how the yeast has done, and it is 1.108 to 1.030; over 70% attenuation

3.5 lbs of speciality grain is a lot, and extract tends to end high too.
 
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Belariad

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I didn't hydrate the yeast before pitching no. I guess you could say I've been going on the simple instructions from my local brew shop so far, and they never mentioned starters or hydrating.

Could you provide a link to a simple yeast starter guide? I don't have much fancy equipment (only started brewing in January) and the guides I've found so far involve erlenmeyer flasks and magnetic stir plates (did I find the overkill methods or is that a normal thing?). Do you mean "a long wait" as in it will eventually ferment on it's own if I leave it? I'm not really in a rush for this one, but I just want to make sure it's somewhat drinkable and carbs in the bottle. We've been super thrilled with our first 4 brews and we haven't done any starters yet (maybe we just have low standards haha).

I'm checking gravity with a hydrometer. I've checked it with straight water and it seems calibrated properly.
 
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Belariad

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I think you are done, and you had a bad OG measurement.

I assume this is 5 gallons.

15 lbs LME in 5 gallons will get you 1.108. Add 3.5 lbs of steeping grains and you are probably closer to 1.120. So you went from about 1.120 to 1.041.

The sugars from the grains are mostly unfermentable, so if I take them out just to figure out how the yeast has done, and it is 1.108 to 1.030; over 70% attenuation

3.5 lbs of speciality grain is a lot, and extract tends to end high too.
Why would brewers friend think my OG would be closer to 1.094 including the LME and steeping grains? I'm pretty sure I used their default efficiency factor for steeping.
 

Quaker

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No need for a starter with dry yeast, just follow the instructions on the packet to hydrate it ahead of time. Nothing fancy is needed. It decreases the shock of the yeast trying to absorb high sugar wort when rehydrating if pitched dry. It may not make a noticeable difference with moderate to low gravity beers due to the high cell count in a packet. But with a big beer, they need all the help they can get.
 

Calder

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Why would brewers friend think my OG would be closer to 1.094 including the LME and steeping grains? I'm pretty sure I used their default efficiency factor for steeping.
What volume did you use?

I checked BF, and got the following. 15 lbs LME in 5.0 gallons is 1.105. 15 lbs LME in 5.5 gallons is 1.095. This is before the unfermentable sugars from 3.5 lbs of steeping grain.

I dialed in 3.5 lbs C60, and it took those numbers to 1.113 and 1.103 respectively using their default efficiency (which is really low).

6 gallons gets it to 1.094.

You have not said what volume you made. I assumed the standard 5 gallons.
 

ArcaneXor

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Purchase a vial or pouch of WLP099 Super High Gravity Yeast and pitch it in there. It will dry it right out. 099 will fix 90% of underattenuated beers with minimal flavor impact.
 

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