Originally Posted by avidhomebrewer
As far as preventing a stuck fermentation to begin with, I'm not quite sure how you would do that. I'd be interested in hearing how.
It's the same as preventing anything. You prevent the cause and then there is no effect. Stable proper temperatures, stable proper mash temperatures, proper pitching rates, etc. I've had one stuck fermentation, it was a Belgian Strong Dark Ale. When it happened I tried everything. I raised temperature and roused the yeast. I made another beer and pitched onto the cake. Finally, I pitched a champagne yeast starter at high krausen. Absolutely nothing worked. It's still sitting in my basement right now. Finished somewhere around 1.028 I think.
So what you do is review what might have gone wrong. For me the first thing was the yeast, it almost always is. I started with an expired pack of yeast and made my starter. I stepped up once, but since it was old I probably should have started smaller and done more steps. Essentially, I don't believe I pitched enough yeast. On brew day, I kept mash temps steady and low, 148F IIRC, but I got better than expected efficiency and overshot my gravity by .006 I think. Which means I needed even more yeast. During fermentation I had trouble keeping the temps up steadily, they would rise and fall 6 degrees or so per day. I also lost a ton of yeast out the blow off tube.
So I won't be doing this beer again until I can keep the temps more steady. I will build my starter to a bigger size, probably just pitch onto a portion of a cake. I will also use some fermcapS during fermentation to prevent a huge blow off. So if I can prevent the issues that may have caused it then I can prevent it from ever happening. You learn a lesson and you move on. Fermentations don't generally get stuck, it is not at all common for yeast to just stop doing their jobs. Somewhere in the process there was an area where you did not give them all the help they needed. Sometimes it can be fixed but not usually.