Stalled fermentation question - Same batch, different readings

[stansoid]

Hello,

I made a batch of beer using a combination of a pre-made wort beer kit and a small AG boil. I mixed all the wort together in a bottling bucket (total of 6 GAL of wort), pitched re-hydrated S-05 yeast into the bottling bucket and stirred it in. OG is 1.068. (see here for the discussion that lead to this experiment https://www.homebrewtalk.com/f39/noob-brewhout-lager-kit-question-502739/ )


I then used the bottling bucket to divide it into 3 fermentation containers. 2 x 3 Gallon carboys (approx 2.5 gal in each) and 1 x 1 gallon carboy and put them into my small chest freezer for temp control. They fermented pretty actively for about a week and a half. They have been in the fermentation chamber for 3 weeks as of today.

Today I took readings. They turned out as follows:

2.5 Gal carboy #1 = 1.018 (by hydrometer)
2.5 Gal carboy #2 = 1.038 (by hydrometer)
1 Gal carboy 1.032 (By refractometer)

It would appear that fermentation in the #2 2.5 gal and the 1 gal carboys has stalled in comparison to the #1 2.5 gal. On the plus side, this frankenbeer experiment seems to taste pretty good when I drank the samples.

I am worried that if I mix them all back together in the bottling bucket and bottle I may be making some bottle bombs.

Any advice on how to get the fermentation going again the 2 higher reading containers? Or will it be fine to bottle as is?

Any thoughts?

 

[buzzerj]

What is the temperature that the beers are currently at? I'm assuming like 65-68 degrees F. One would think the beers would have finished if they've been fermenting for that long. They should be near finished by the 4-7 day mark. Any yeast nutrient added? It's odd that the variance between the two fermenters measured with the same hydrometer. I personally would not trust the refractometer reading. I'd take the readings over again with a sanitized hydrometer. I trust hydrometer readings for beer more. But I'd also measure room temp water with the hydrometer to see that it reads 1.000. How long was the duration between pitching the yeast and racking to the carboys? I assume all the carboys were sanitized. I would assume the pH of each portion of beer would be about the same. I haven't had stalled fermentations myself but I have seen labored fermentations in wines when the must is too acidic. I'd be interested in what you uncover.

 

[stansoid]

The beer is sitting at at about 63 F. They all went into cleaned and sanitized fermeters at the same time.

No nutrient added.

I also don't trust the refractometer. I just can't get a good sample out of the 1 gal carboy for the hydrometer .

The yeast was pitched, stirred and then it was racked all within about 10 minutes.

Its an interesting problem for sure. I may bottle it and then leave the bottles in their case inside a garbage bag for a week or two.

 

[buzzerj]

Yeah it is interesting. When you rack the one gallon or are bottling it, fill a sanitized cylinder and get a hydrometer reading. If it did stall I think you are likely to have a real sweet beer more than the chance of having bottle bombs. I don't see that yeast restarting once bottled. What is really odd is that Carboy #2 reading. If all carboys were held at the same temperature, one would assume the fermentation would be the same rate given the same yeast was pitched in three portions of the same wort. I usually primary my 5 gallon batch in a 6 gallon carboy for one week and by that time the beer is usually done. I don't pitch yeast into wort until I know what the wort temp in the primary is. So I pitch the yeast only after I transfer the wort into the primary. The only thing I can conjecture is maybe the portions in Carboys #2 and #3 remained in hotter wort for a longer period than the portion in Carboy #1. But still those portions of the wort did ferment to some extent before stalling. Do you know the wort temperature at the time you pitched? Try raising the wort temperature 5 degrees and see what happens.

 

[stansoid]

I think I will raise the temperature up to 67 F and see if it picks up. Do you think its worth giving the yeast cake a quick stir?

 

[buzzerj]

I don't think it will hurt if you use a sanitized spoon and don't drive O2 into the beer.

 

[stansoid]

I set my temp controller for 68 F and opened the freezer overnight to let it start to rise. They are currently at about 65F and rising.

I also opened up all three carboys last night and gave them a gentle stir to get the yeast cake roused up (being sure not to slosh around and bring oxygen into the mix).

As of this morning they are all back to life. The two that were at 1.03X levels more than the 1.018, but all three are showing active airlock activity.

 

[madscientist451]

Hopefully the higher temp will let them all finish off. The only thing that I can think of is that the rehydrated yeast sank to the bottom of your original container and you ended up with an uneven amount of yeast in the 3 fermentors. Divide the wort up before pitching next time, then divide your yeast and add it. Or just get two packets.

 

[stansoid]

I am thinking it might be worth while to repitch. I am worried about bottle bombs if it doesn't finish up nicely.

 

[stansoid]

Quick update on this..

I stirred it up and raised the temp from about 63F to 67. It started fermenting again slowly. I repitched it with another pack of the same yeast (S-05).

The carboy at 1.018 bubbled mildly for 3 days and has stopped. I suspect its completed now.

The two carboys in the 1.03x range are still fermenting. This appears to have solved my problem.

Next time I do a big beer I will be sure to pitch 2 package of yeast or make a starter.

Thanks for the input everyone.

 

[chickypad]

If using the refractometer you need to do the correction for the presence of alcohol. I find this calculator to be pretty accurate for mine when tested against a hydro reading, though YRMV. It would at least be a lot closer than the uncorrected reading.