Low Attenuation issues

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tubbsy

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The last 2 batches of beer (London Porter and a Dark Mild) had both had very low attenuation, but each batch was done differently.


The Mild was my first foray into BIAB and I thought it went pretty well, although I've since realised the temperature on the STC-1000 was reading several degrees low so I probably mashed at ~70C instead of 68C. The thermometer I used for the porter (with the traditional mash in the esky) reads pretty accurately though.

The OG on the porter was higher than expected (1.052 vs 1.046), but finished at 1.019.
The OG on the mild was pretty much as expected (1.035 vs 1.034), but finished at 1.016 which is a much lower ABV than I was aiming for. It's currently cold crashing, but I'm open to suggestions on giving it a kick in the guts to get it moving again.

I used different yeasts, but both were pitched dry as I figured they could handle the low SG.

The only similarity in the process was I used my DIY counterflow chiller. I also just realised my wort was probably pretty low in oxygen as there was minimal splashing into the fermenter.

Besides the lack of oxygenating the wort, is there anything else that stands out as being a cause for the low attenuation?
 

duncbrewer

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What yeasts did you use.

Tubbsy recipe comes to 4.4% and you are at 4.33%.

How long did you ferment for ? did you raise temp at end to help it clean up and finish?

Higher mash temp will make more unfermentables but you felt your porter mash was okay temp wise. The higher for the mild though may be the cause of the Higher final SG.
 

tubbsy

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What yeasts did you use.
I used London III 1318 for the porter and Nottingham on the mild.

Tubbsy recipe comes to 4.4% and you are at 4.33%.
Yes, that's because I had a better efficiency and got a 6 point higher OG.

How long did you ferment for ? did you raise temp at end to help it clean up and finish?
Both fermented at 18C for 3-4 days then 21C for the remainder of the ferment.

The Porter reached terminal FG on day 6 and the Mild on day 3. Total ferment times were 9 and 7 days, respectively.

Higher mash temp will make more unfermentables but you felt your porter mash was okay temp wise. The higher for the mild though may be the cause of the Higher final SG.
I was using a T500 boiler which I have put a thermowell in. I used a STC-1000 to control the temp and had another thermometer at the top and they both compared pretty well at the time, but in reality the bottom was probably several degrees hotter. I might try the Mild again after I calibrate the STC-1000.
 

duncbrewer

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I have seen some interesting temp variance with my STC 1000 in the ferment fridge and have had to calibrate it for the hot ferments ( kveik at 34 C ) and then recalibrate again when it was cold crashed ( realised I had a misread when there was a beer burg floating in the top of the fermenter ) .
 

MHB

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If part of the mash is hotter that part will have lower attenuation.
It’s almost certainly mash temperature issue. In most cases you are way better off just doing the strike water temp calculation, mashing in, stirring well and leaving it the hell alone. Applying heat unless it’s done well will cause more problems than it will benefits.
Mark
 

scomet

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G’day tubbsy, Good question. When I started seriously brewing 'all-grain' my beers (ales) would always finish around 1018 1015ish I thought it was BS people could get to 1004 or less!
These days my general brews, Bitters Pales etc. using the same yeast type, never finish above 1005. My last pale ale mashed at higher temps got down to 1003! and it was a bigger beer! So apart from yeast type “why is this so”
I put it 85% down to good yeast management. I rehydrate dry yeast, I oxygenate my wort, temperatures and differential temperatures are critical to good yeast health as is the timing when you inoculate, how long you rehydrate for etc, the list goes onnn, but worth the effort. The book Yeast in the brewing series is a good read if you want to get serous about yeast health. CHEERS
ps. the other 15% is sanitation… Oh, and I never get 'volcanoes' any more.. Just try one of these ideas and see if it lowers your fg.
 

elmoMakesBeer

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I agree mash temp is a likely culprit. But I did have a stalled ferment with London Ale III (your original post said you pitched dry - not sure how you do that with a liquid yeast) recently with an IPA.
After 4 days fermenting at 19.5deg it had reached about 60% attenuation (sg at 1.025 down from 1.064). It stayed there for another 3 days. The krausen was still thick and showing no signs of dropping for I gave the fermenter a good shake and ramped the temp to 22deg. After a couple more days it stopped again at 1.017, which was 72% attenuation, which is in the 71-75% published range, and I called it done.
My last brew (an amber ale), using the same yeast I fermented at 20deg for 4 days (62% attenuation) then stepped up the temp a couple of times as it slowed (I didn’t let it stall completely) to 21.5 then 22.5deg. It was done in 9 days reaching 75% attenuation (1.014 down from 1.057).
 

scomet

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Sorry forgot over-pitching, I put about 22g of Notto into a 25L standard beer (buy in bulk savada da money)
 

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