Common causes for stuck fermentation

[mgr_stl]

I had my first stuck fermentation on my most recent brew (milk chocolate stout). OG 1.054 and only got down to about 1.030. My fermentation temps were within the recommended range (S-04) and I did my typical shake the carboy like hell for about a minute before pitching the yeast.

I pitched another pack of yeast, and it seems to be starting back up.

One worker at the LHBS thought that it might be a result of rehydrating the yeast, which I thought was a weird suggestion. Don't see how rehydrating could cause a stuck fermentation unless my temperatures were off and I rehydrated too hot.

So what are the most common reasons for a stuck fermentation?

 

[Calder]

Recipe? All grain or extract?

......... and did you measure FG with an hydrometer or refractometer?

 

[mgr_stl]

Extract.

I measured with a hydrometer and then brought my sample to the LHBS to make sure it wasn't a hydrometer issue. They measured it with theirs and, although my hydrometer war off by about 0.006, they agreed that something had gone wrong and it did not finish fermenting.

 

[falkaveli]

What temperature are you fermenting at? Is it constant-ish?

 

[mgr_stl]

I have a fermentation chamber and the probe was attached to the side of the carboy between it and a chunk of foam. 63 degrees for the first five days and 65.5 for the rest.

I forgot to mention the original brew date was mid February.

 

[Clarke]

US-04 I have read and experienced, is a stop short kind of yeast. It is a fast fermenting and high flocculation yeast, it will drop before the job is done, usually agitating it will get it moving again, if your agitation didn't get it going, I don't really know and I would do the same as you and add more yeast. I would also raise the temp to the higher end of the yeast preference to finish it out.

 

[falkaveli]

Yep, I bet you it was that low fermentation temperature. A slightly higher temperature and a bit of agitation if your fermentation slows will get you back up and running.

 

[BlueHouseBrewhaus]

You mentioned that it's a milk stout. That usually means adding lactose. How much did you add? Too much can be a problem since it is unfermentable.

 

[mgr_stl]

There was a pound of lactose.

Also, it's been set at 70 degrees since repitching. Not much visual activity, so I'll do a gravity reading in a couple days.

 

[BrewHound]

US-04 I have read and experienced, is a stop short kind of yeast. It is a fast fermenting and high flocculation yeast, it will drop before the job is done, usually agitating it will get it moving again, if your agitation didn't get it going, I don't really know and I would do the same as you and add more yeast. I would also raise the temp to the higher end of the yeast preference to finish it out.

+1 on that. The first time I used us-04 it stalled on me.

 

[BigFloyd]

+1 on that. The first time I used us-04 it stalled on me.

Another member of the "I've had S-04 stall on me" club here. It was a coffee porter that stuck at 1.024. Warming a few degrees to 70*F and a gentle stir with a sanitized spoon only coaxed it down to 1.022 after a week. Kegged it with cold brewed dark roast coffee. Tasted great.

 

[mgr_stl]

The main thing I'm concerned about is that I bottle and don't want any bottle bombs if it all of a sudden decides to resume fermentation.

 

[Clarke]

The main thing I'm concerned about is that I bottle and don't want any bottle bombs if it all of a sudden decides to resume fermentation.

I have never had a bottle explode on me but some of my beers have had me concerned. What I do or used to do when bottling...

I have a collection of 12 pack boxes, completely enclosed except for the handle holes. I put all my bottles in these, then I put the boxes in a heavy duty black garbage bag.

The box will hold the glass and the bag will hold the beer, if by chance they do explode. I am not so diligent on this as I used to be, but it is an idea for the worried mind.

 

[Calder]

I've had a bottle go on me. It was a stout. Seemed to have finished at 1.016. I checked the gravity of another bottle after the one broke, and found it had dropped a further 9 points.

I would be worried about the bottles.

If it were me and I was out of options, I think I'd bottle, and check bottles weekly to see how the carbonation is going. Once carb'd, I would move all bottles to a fridge, and drink fairly quickly.

 

[BigFloyd]

The main thing I'm concerned about is that I bottle and don't want any bottle bombs if it all of a sudden decides to resume fermentation.

A legitimate concern indeed.

Since you're bottling, you may want to warm it to 70-72*F then a gentle stir the next day to get that yeast cake back up into suspension followed by 10-14 days at that temp. See where you're at then.