Stuck fermentation

[HESPEBAY]

hi guys,
I am Fabien from France.
I brewed this little PA (see after).
My fermentation is stucked at 1026. Do you see anything in this receipt that could justify such a stuck fermentation ?
If you have any other comment on the receipt, please feel free to advise.
Many thanks,

Fabien

Boil Time: 60 min
Batch Size: 23.5 liters (ending kettle volume)
Boil Size: 26 liters
Boil Gravity: 1.047
Efficiency: 70% (ending kettle)
No Chill: 10 minute extended hop boil time

STATS:
Original Gravity: 1.052
Final Gravity: 1.015
ABV (standard): 4.92%
IBU (tinseth): 37.32
SRM (morey): 9.37

FERMENTABLES:
3.5 kg - Belgian - Pale Ale (62.8%)
1.5 kg - German - Pilsner (26.9%)
0.5 kg - United Kingdom - Crystal 50L (9%)
75 g - Belgian - Biscuit (1.3%)

HOPS:
12 g - Ahtanum, Type: Pellet, AA: 4.6, Use: First Wort, IBU: 3.71
2 g - Willamette, Type: Leaf/Whole, AA: 4.7, Use: First Wort, IBU: 0.57
11 g - Magnum, Type: Leaf/Whole, AA: 14.5, Use: Boil for 60 min, IBU: 16.6
10 g - Willamette, Type: Pellet, AA: 4.7, Use: Boil for 45 min, IBU: 5.09
8 g - Ahtanum, Type: Pellet, AA: 4.6, Use: Boil for 15 min, IBU: 2.84
5 g - el dorado, Type: Leaf/Whole, AA: 15.5, Use: Boil for 7 min, IBU: 4.24
5 g - Ahtanum, Type: Pellet, AA: 4.6, Use: Whirlpool for 10 min at 90 °C, IBU: 0.98
5 g - el dorado, Type: Leaf/Whole, AA: 15.5, Use: Whirlpool for 10 min at 90 °C, IBU: 3.3

MASH GUIDELINES:
1) Temperature, Temp: 55 C, Time: 5 min, Amount: 25 L
2) Temperature, Temp: 63 C, Time: 60 min, Amount: 25 L
3) Temperature, Temp: 68 C, Time: 15 min, Amount: 25 L
4) Temperature, Temp: 73 C, Time: 5 min, Amount: 25 L
5) Temperature, Temp: 78 C, Time: 10 min, Amount: 25 L
Starting Mash Thickness: 4.86 L/kg

YEAST:
Fermentis / Safale - American Ale Yeast US-05
Starter: No
Form: Dry
Attenuation (avg): 72%
Flocculation: Medium
Optimum Temp: 15 - 23.89 C
Fermentation Temp: 19 C
Pitch Rate: 0.75 (M cells / ml / deg P)

 

[Ozarks Mountain Brewery]

how did you add oxygen, and how many days since you brewed

 

[social_misfit]

did you rehydrate the US-05? maybe raise you temp to 20c (68f) and give it an swirl to rouse the yeast

your mash temp was 145 F which to me is a bit low

I am so bad a metric sorry an American but it looks like you mashed at .58 gallons per pound of grain which to me is a on the thin side

so mashing cold and thin I believe gives you more long chain sugars which do not ferment as well

just my 2 cents

S_M

 

[The Brew Mentor]

I agree with the above comment on mash temp.
An old standard was a 40/60/70 rest schedule with a 30 minute rest at each temp.
The grist ratio should be 2 -2.5 L/kg.
The thinner mash will dilute the enzymes and also raise the ph making conversion much more difficult.
You could try adding some Amylase enzymes to the fermentor now, give it a swirl and warm it up a bit. Give it another week or so at the warmer temperature and you should drop the gravity a bit.
Today's grains are modified enough to convert completely with a single infusion mash. Give that a try on the next batch and let us know how it turns out for you.
Good Luck
Brian

 

[MrBIP]

Agree that 145 seems low.
But, lower mash temp should result in a more fermentable wort.
Is it possible that at 145 and not enough time there was a failure/shortage in conversion -- extremely low conversion efficiency? And would that yield a wort that would not fully ferment, leaving FG high like this?

 

[The Brew Mentor]

Correct.
When mashing at lower temps, you need to extend the rest to insure conversion and then check it with Iodine. Otherwise you make starch soup.
I just did a low temperature mash(148°) with ~20% adjuncts in it and it took 2 hours to complete.
On the other end, I did a high temperature mash(158°) and it was fully converted in under 20 minutes.
Hope this helps,
Brian