Inconsistent fermentation in similar temperature conditions

[Brewer #439361]

Hi

I have made a pretty good brew that consistently starts at about 1.032 SG and usually ends at 1.010 , however twice now it's ended at 1.020

(I'm brewing an ale BIAB, leaving it in a fermenter for 7 to 10 days , taking the "end" SG reading and then bottling it up.)

I'm trying to figure out what's going wrong with the batches that end at 1.020 ... the first was in a cold spell in Brisbane, with temps likely several degrees below 12C and adding more Yeast and leaving it for another week did nothing (assuming it died).

Surprisingly, despite the SG remaining at 1.020, bottling the beer resulted in beer with full strength alcohol content. As i assumed the SG would reflect alcohol content. However it has a very thick and unrefined, comparatively dirty sort of consistency and is "drinkable" rather than "good"

I assumed it was temperature, but now I've just done a batch in perfect weather (15C to 22C all day every day) and it's happened again. Does anyone have any idea as to the factors causing this? My only guess is that brewing without temperature control is inconsistent in results and maybe I should double the yeast I put in to make it work, but I'm very thrown off by the fact it still seems to have full alcohol content.

I guess it could be the temperature that I Mash, but I'm skeptical that it makes that much difference. I may try really carefully to recreate the temperature conditions recorded on my successful batches to make the wort identical. But I find it hard to believe that 10 degrees celcius mashing malt makes such an extreme difference in the quality of the beer.

Have a good one and don't drink too much

 

[Minbari]

Hi

I have made a pretty good brew that consistently starts at about 1.032 SG and usually ends at 1.010 , however twice now it's ended at 1.020

(I'm brewing an ale BIAB, leaving it in a fermenter for 7 to 10 days , taking the "end" SG reading and then bottling it up.)

I'm trying to figure out what's going wrong with the batches that end at 1.020 ... the first was in a cold spell in Brisbane, with temps likely several degrees below 12C and adding more Yeast and leaving it for another week did nothing (assuming it died).

Surprisingly, despite the SG remaining at 1.020, bottling the beer resulted in beer with full strength alcohol content. As i assumed the SG would reflect alcohol content. However it has a very thick and unrefined, comparatively dirty sort of consistency and is "drinkable" rather than "good"

I assumed it was temperature, but now I've just done a batch in perfect weather (15C to 22C all day every day) and it's happened again. Does anyone have any idea as to the factors causing this? My only guess is that brewing without temperature control is inconsistent in results and maybe I should double the yeast I put in to make it work, but I'm very thrown off by the fact it still seems to have full alcohol content.

I guess it could be the temperature that I Mash, but I'm skeptical that it makes that much difference. I may try really carefully to recreate the temperature conditions recorded on my successful batches to make the wort identical. But I find it hard to believe that 10 degrees celcius mashing malt makes such an extreme difference in the quality of the beer.

Have a good one and don't drink too much

That makes a huge diffrence. Mashing at 146F vs 155F will yield a very different mash. The higher temp having less fermentable sugars and it will finish higher, with more residual sweetness

 

[Brewer #439361]

That makes a huge diffrence. Mashing at 146F vs 155F will yield a very different mash. The higher temp having less fermentable sugars and it will finish higher, with more residual sweetness

Yeah it's interesting you say that because id assume with less fermentable sugars it would be lower alcohol. But it is in fact HIGHER alcohol than the other one. I'm guessing I've just mashed in some really crazy sugars. I'll reply to my own post with some objective results if I can get this consistent based on my successful brews mashing temps but I might take a while. Thanks for your fast reply and have a good day

 

[Zambi]

How do you know it is higher in alcohol?

How do you measure your SG? If you use a refractometer, you need to use a correction table as a refractometer does give a wrong reading in the presence of alcohol.
1.032 to 1.020 gives an alcohol percentage of just 1.5%, but if measured with a refractometer (without correction) it's around 2.5%
1.032 to 1.010 gives 4.4 % and 2.9 % resp, but a very high apparent attenuation, so I don't think you use a refractometer.

I also think it is in the mashing, but wouldn't rule out measuring inconsistencies

 

[Minbari]

How do you know it is higher in alcohol?

How do you measure your SG? If you use a refractometer, you need to use a correction table as a refractometer does give a wrong reading in the presence of alcohol.
1.032 to 1.020 gives an alcohol percentage of just 1.5%, but if measured with a refractometer (without correction) it's around 2.5%
1.032 to 1.010 gives 4.4 % and 2.9 % resp, but a very high apparent attenuation, so I don't think you use a refractometer.

I also think it is in the mashing, but wouldn't rule out measuring inconsistencies

This

If you are measuring correctly. A higher FG will be less abv if the starting OG was the same

 

[BarbarianBrewer]

A hydrometer will be more accurate than a refractometer when alcohol is present. But, hydrometers need to be calibrated in plain water (preferably distilled water). I have used numerous hydrometers. Usually they are off by a point or two but one was off by 4 gravity points! Didn't really matter though because I just had to add or subtract the correction value to get a true gravity reading. Also, hydrometers are calibrated at a specific temperature. The further away from the calibration temperature the wort is, the further off the gravity reading will be. I use this calculator to adjust hydrometer readings based on temperature.

Cool fermentation temperatures would make for sluggish yeast but it wouldn't kill the yeast. In this case I think if you waited for the weather to warm up and then gave it another week, it probably would have dropped a few more points; maybe down to your target FG. One possible problem with cold, old, or weak yeast is that it will take longer for them to start fermenting and producing alcohol which keeps bacteria or wild yeasts from gaining a foothold. But, as long as your sanitation is good, this shouldn't be too much of a concern.