Gravity went from 1.105 to 1.066 and stopped

[Jean-François Beauchamp]

Hi!
I brewed a Wee Heavy 10 days ago (on December 16), and the airlock bubbled only for a day. Still, I left the beer sitting in the fermenter for 9 days, and I took readings yesterday, and today. The gravity is not moving anymore, and it is at 1,066. The OG adjusted for 20 C was 1,105. The expected FG for that beer should be 1.026. Is this normal? If I transfer the beer to a a carboy, is there any chance for the fermentation process to resume and lower the gravity down to 1.026 from 1.066?

Cheers!

JF

 

[Calder]

What did you measure the FG with. If it is a refractometer, then you need to convert the result.

Need more details to help otherwise, but 66 to 26 seems like a real stretch for a fermentation that seems to have ended.

 

[Jean-François Beauchamp]

I measured the OG with a hydrometer, and corrected the reading for 20 C. Since then, I got a refractometer that I used for my last two gravity readings (1.066).

According to the recipe, the OG should have been 1.099. However, it only reached 1.077 at 57 C (135 F) or a gravity of 1.089 once corrected for 20 C. So I added 250 g (half a pound) of DMG 5 minutes before the end of the boil to augment the gravity. This is how my OG reached 1.094 at 54 C or 1.105 once corrected for 20 C.

I am wondering what would have stopped the fermentation. I used Edinburgh Ale Yeast (White Labs-WLP028), and the temperature during fermentation was always between 17 C and 22 C (63 F to 72 F).

 

[Calder]

Refractometer readings are inaccurate after fermentation has started and alcohol is present (it is also inaccurate for OG measurements - but ok for general use as an OG measurement). Refractometers measure simple sugars in water, and when you have alcohol present is screws up the measurement.

There are calculators on-line that you can use to convert refractometer readings to actual FG readings.

My brewing software seems screwed up, so can't do the numbers for you, but I think that once you process the numbers you will find you are at least 30 points lower.

Maybe take an hydrometer reading.

 

[RM-MN]

I measured the OG with a hydrometer, and corrected the reading for 20 C. Since then, I got a refractometer that I used for my last two gravity readings (1.066).

According to the recipe, the OG should have been 1.099. However, it only reached 1.077 at 57 C (135 F) or a gravity of 1.089 once corrected for 20 C. So I added 250 g (half a pound) of DMG 5 minutes before the end of the boil to augment the gravity. This is how my OG reached 1.094 at 54 C or 1.105 once corrected for 20 C.

I am wondering what would have stopped the fermentation. I used Edinburgh Ale Yeast (White Labs-WLP028), and the temperature during fermentation was always between 17 C and 22 C (63 F to 72 F).

Depending on when and how quickly the temperature changed in that range you might have caused the yeast to stall out. Yeasts seem to like stable temperatures and your 63F is a bit on the low side of the preferred range. I'd give the fermenter a swirl to re-suspend the yeast and put it in a warmer place for a few days, something in the 22-24C range. Be sure to use a hydrometer as they will be more accurate than the refractometer, especially with higher amounts of alcohol present.

 

[myndflyte]

If you use this calculator: http://seanterrill.com/2012/01/06/refractometer-calculator/ and assume your starting Brix was about 25, you're gravity is coming out to about 1.08 so it looks like you've stalled. The tips that @RM-MN gave are a good place to start to try getting the fermentation going again. Nothing jumps out as the yeast being finicky. Did you make a starter with this or just pitch the vial?

 

[Calder]

Depending on when and how quickly the temperature changed in that range you might have caused the yeast to stall out. Yeasts seem to like stable temperatures and your 63F is a bit on the low side of the preferred range. I'd give the fermenter a swirl to re-suspend the yeast and put it in a warmer place for a few days, something in the 22-24C range. Be sure to use a hydrometer as they will be more accurate than the refractometer, especially with higher amounts of alcohol present.

I think his problem is that he used an Hydrometer for the initial reading, and a Refractometer for the FG and didn't correct for the alcohol.

Using my BeerSmith calculator (tailored to my refractometer): OG: 1.105, FG: 16.11 Brix, results in an FG of 1.041.

Still very high, but a more reasonable 60% attenuation. I would wonder if the temp dropped late in the fermentation and the yeast stalled. Warming up to ~70 F may help.

 

[Jean-François Beauchamp]

Thank you very much for all your help! I did not know that a refractometer was not giving a good reading in the presence of alcohol, so yesterday, I transferred my beer to a carboy, and I used the opportunity to measure the gravity with a hydrometer. So the correct gravity is 1.040, which makes more sense even if it is not as low as what the FG should be, yet.

@Calder: What did you mean when you said that refractometer readings are also inaccurate for OG measurements?

@myndflyte: I just pitched the vial. But it is a small batch. I just did half a recipe (around 3 gallons).

Concerning the temperature, it goes up and down depending on the temperature outside and how much I live my pantry door open. We currently have -5 F here in Montreal, so the pantry door is opened quite a bit.

 

[myndflyte]

I think he was saying that out of the box, refractometers can be inaccurate until you've figured out the right correction factor for your meter. The best way to determine that is to take refractometer and hydrometer readings before you pitch yeast and plug them in something like this: https://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/.

This will give you an average correction factor to better estimate gravity from your refractometer.

 

[Smellyglove]

And don't take hydrometer readings way above the temp the hydrometer was calibrated to. Imho you don't know the OG since the measurement was done at a high temperature.

 

[Calder]

@Calder: What did you mean when you said that refractometer readings are also inaccurate for OG measurements?

Refractometers read simple sugars, we have a lot of complex sugars in wort, so the reading is inaccurate as a result.

I think he was saying that out of the box, refractometers can be inaccurate until you've figured out the right correction factor for your meter. The best way to determine that is to take refractometer and hydrometer readings before you pitch yeast and plug them in something like this: https://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/.

This will give you an average correction factor to better estimate gravity from your refractometer.

As noted, you can 'calibrate' your refractometer, but it will only be good for the wort you used to calibrate it with. A highly fermentable Belgian will give different results compared to a wort of the same gravity for a heavy Barleywine, so use an 'average' style to figure out your correction. We are only talking about a couple of points variation, so nothing to be really concerned with once you know your correction factor.

There are on-line correction factors, all of which have been created from empirical data (average of lots of measurements of different types of wort).

 

[Calder]

I transferred my beer to a carboy, and I used the opportunity to measure the gravity with a hydrometer. So the correct gravity is 1.040, which makes more sense even if it is not as low as what the FG should be, yet.

Concerning the temperature, it goes up and down depending on the temperature outside and how much I live my pantry door open. We currently have -5 F here in Montreal, so the pantry door is opened quite a bit.

That's cold ... we are a whopping 10 degrees higher down here overnight. I think we went over 20 F today.

If the beer has gotten cold (low 60s, or lower), the yeast can slow or even stop fermenting. If it stops, it drops too. If that was your problem, and you transferred to secondary while the yeast were cold or dormant, you will have left a lot of the healthy yeast behind. Never (never, never, never ..... rack off the yeast until you know you are at FG!!!!!).

All is not necessarily lost. You have some yeast, and it will slowly work if there are sugars left if you warm it up, but it is a big beer which doesn't help with yeast health.

Warm it up, let it go and see where it ends up and come back. If it doesn't get down much, you can make a starter from the yeast that drops in the secondary and then feed the starter with the beer so as not to shock the yeast too much.

 

[JonM]

A nearly foolproof way to un-stick a stuck fermentation is to brew another batch - an average gravity ale - let it ferment, rack it off its yeast cake then rack the stuck beer onto that yeast cake. Fermentation should start up right away and finish the job.