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I have made a batch of Marzen/Octoberfest. I brewed it 3 weeks ago. Starting gravity was 1.060, the beer was well airated. I have used WLP820 with 1.7L starter. It's fermenting in my fridge at 50F. It's bubbling (like every 4-5 seconds), so yeah, it is still fermenting. Right now the gravity is 1.029. Yep, it goes down by .010 every 7 day. It is my second lager batch (I brewed a schwarzbier on the same week). Interesting enough, Schwarzbier fermented to 1.016 in just 2 weeks.

The problem is that I am leaving next Thursday for two weeks and most likely the fermentation would stop in that period. I just didn't expect it to go that slow and thought giving it 4 weeks would be sufficient.

My question is... Should I just leave it as it is and go for my business trip without worrying about anything, and do a diacetyl rest after coming back from the trip. Or is there anything I can do, to speed up the process without any harm to the batch, like adding yeast energizers or even 2L of new healthy yeasts (though not sure if I would have time to make 2L starter)?

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To fix this beer, I would raise the temperature to 55F and leave it for another couple of weeks. Assuming sanitation is good the beer will be ok.

1.7l is on the small side even for a stirred starter for a 1.060 lager, and airation doesn't provide the dissolved oxygen levels needed. (ca. 15ppm.) In future, aim for a 4-5l starter and yeast nutrient. If you can get a source of oxygen and an a 0.5micron diffusion stone that will improve your lagers.

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    To be clear, don't add the oxygen now. @mdma's point is that oxygenating the wort before pitching the yeast helps with the yeast's growth (i.e. aerobic) phase. – FishesCycle Jul 9 '15 at 5:06
  • Yeah, I won't be adding any oxygen to it at this point :). Now about the starter... 1.7L came from the calculator tool (forgot the name of it). Next time I'll be doing a gallon starter. I'll raise temperature to 53-55 and will keep it until 30 July (that's when I come back). Hopefully it would be okay by then. I was planning to enter it into Octoberfest competition, but it seems that my chances are getting are getting smaller. I guess, in the worst case, I'll just drink it with my friends. Thanks. – Trigger Jul 9 '15 at 22:16

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