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I was just curious because I took what was supposed to be my OG two days after because my hydrometer came late. The reading seemed very low, 1.030, and I was hoping I lost at least .010 from the first two days of fermenting. I used Safale US-05 yeast, pitched at around 90 degrees and let it ferment at 68-72 degrees. Desired OG was 1.052. Since I'm using a bucket I'm not able to see any foam, but activity in the airlock started less than 20 hours after pitching yeast.

  • There are many variables that can influence the speed of fermentation. Please share at least which yeast was pitched, what temperature did it ferment in, what was the desired OG. – slawekwin Sep 21 '16 at 11:45
  • So you used one sachet of not rehydrated yest, yes? Also, how much time did it take for the foam to appear and airlock to show any action? – slawekwin Sep 21 '16 at 12:00
  • Since I'm using a bucket I'm not able to see any foam, but activity in the airlock started less than 20 hours after picking the yeast. – Ryan Whelan Sep 21 '16 at 12:22
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I don't believe there is a exact formula to calculate this, but I think that 1.052 would take about 4 - 5 days to ferment with US-05, maybe even less in this temperature. Judging by relatively quick airlock action, I would assume the yeast is in good health. Also, it is worth mentioning that the fermentation is fastest in the beginning, just after the yeast is done multiplying.

I would estimate that you can be sure that it was at least 1.040 and your desired 1.052 is quite possible.

Have you verified your calculations for amount of fermentables with some kind of calculator (I use e.g. brewersfriend)? If you have calculated the amount of malt to match your target OG, then there is a good chance you were not off by much.

  • Also, airlock activity stopped after about 4 days. Your calculations are probably right. Thank you! – Ryan Whelan Sep 21 '16 at 12:38
  • I didn't get that the fermentation has finished from your question. What was FG? – slawekwin Sep 21 '16 at 12:40
  • I will have to check tomorrow when I transfer to the secondary – Ryan Whelan Sep 21 '16 at 13:45
  • Finished gravity was 1.016 – Ryan Whelan Sep 22 '16 at 4:50
  • In the future I'd suggest being very hands off after you take the OG. Wait 2 weeks then do another reading. – DHough Sep 22 '16 at 15:13
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You are asking about typical fermentation, there is this from UC Davis relating to wine fermentation: http://wineserver.ucdavis.edu/industry/enology/fermentation_management/wine/problem_fermentations.html

Regarding fermentation in beer this article has a graph that shows gravity vs time for 3 strains of yeast: http://www.virtual-labs.leeds.ac.uk/brewing/fermentation/

Given ideal temperature control and nutrition available to yeast you should be able to get fully fermented out in 4-5 days. This is difficult for a home brewery to achieve, but what you have seen ~1052 to 1030 in two days does not seem at all unreasonable to me.

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