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I'm currently fermenting a spiced dark lager with an original gravity of 1.064. I began fermentation 2 weeks ago today with a White Labs 830 yeast that I made a starter with. The yeast was a bit old, so I wanted to make sure the starter was going well before I pitched it into the wort. However, this was my first starter (and lager for that matter), so I may not have produced a large enough yeast batch. Fermentation did start vigorously within about 12 hours after pitching.

A couple of days ago, all signs of fermentation have slowed dramatically. The airlock passes a bubble maybe once every 5 minutes. Taking a specific gravity reading shows a steady level of 1.0333 which gives an attenuation of only about 40-45%. The primary fermentation stage for this recipe called for 4 weeks at 50F, so I'm still 2 weeks before that. At this point I'm thinking I didn't have a large enough yeast starter made.

I've got a packet of Salflager w-34/70 yeast which is similar to WLP830, so I was thinking of racking to the second fermenter and pitching this dry yeast.

What's the right thing to do at this point? Just be patient?

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    Yes, be patient. How big a starter did you make? What was your procedure? How are you maintaining temps? Optimum temp for that yeast is 50-55F--maybe your fridge is swinging a bit lower?
    – JoeFish
    Dec 13, 2012 at 16:59
  • It was a 650 ml bottle for the starter, so not all that big. I've got a temperature controller hooked up a fridge and a warming wrap around the carboy and a sensor in the middle of the wort. Temps are real steady between 50-52F.
    – dcgibbons
    Dec 13, 2012 at 17:05
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    That is pretty small--I try to step up to at least 1 gallon (3.8L) for liquid lager yeast. That said, if you had good activity to start with, it should be fine. The only think I might do is up the temp closer to 55F.
    – JoeFish
    Dec 13, 2012 at 17:30
  • Agreed. The starter was way too small, but whats done is done. If there is yeast in there, and they are alive, they should eventually do their job. You may want to double check all your temperatures. Also, you may find that you have some off flavours from the stressed yeast. Time will help subdue some of those flavours.
    – David PGB
    Dec 14, 2012 at 0:55

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Definitely be patient. fermentation at lower temps (even 50deg F) is slower than the higher temps, so it will likely take longer to attenuate...maybe even longer than the suggested 4 weeks. I would definitely make a bigger starter for future batches. You may need to pitch another starter to get full attenuation though.

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  • At what point would you pitch a new starter?
    – JoeFish
    Dec 19, 2012 at 16:10
  • I would do it sooner (now, if it was me) rather than later, though I don't have any direct experience with doing that (only what I've read).
    – pinkeerach
    Dec 19, 2012 at 16:38
  • Hmmm... so I was out of town for the past week, and checked it again today at 3 weeks again. It has moved some. The SG is down to 1.027 so the attenuation is at 45% now. Just a tiny bit a movement in a week. I did rack it to a secondary last week.
    – dcgibbons
    Dec 21, 2012 at 18:00
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Warm it up to 55. Once there, swirl the whole fermentor to get much of the yeast back in suspension. Hope for the best. You might want to start a 1-2L new starter of the same yeast and pitch it at high krausen if that doesn't work out.

Be patient as it might take more that the 4 week total you were hoping for.

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