Ask Mr. Wizard

Revitalized Fermentation


Michael George • Decatur, Illinois asks,

I am an extract and partial mash brewer and I’ve encountered an odd phenomenon on a couple of occasions, the most striking example of which came this week. I started out to brew a brown porter, though my creativeness got out of hand and I ended up with an OG of 1.084, pretty high for anything that I typically brew. I often use the yeast from a previous batch, and this time, I used the yeast from a batch of pale ale, along with good doses of yeast energizer and nutrient, since the gravity was so high. The airlock started bubbling away about an hour later, which is typical when I reuse yeast. However, after three days, the activity slowed considerably, to one or two gurgles per half hour. Because I knew this is a pretty weighty beer, and because I was out of town, I left the beer in the primary fermenter. It has now been 18 days. I was ready to transfer to the secondary fermenter, when I noticed that the activity had picked up considerably. It’s now bubbling three to four times per minute, what I would expect on day four or five in a typical brew cycle. On a related note, the pale ale in the secondary fermenter had a resurgence of activity, as well. I’ve been monitoring the temperature, and there aren’t any changes from what my brews normally experience. Do you have any idea what might cause such a wide ebb and flow?

I have seen this type of unusual behavior before. Most of the cases I have personally noted have been due to under-pitching yeast. Most brewers agree that pitching rate should proportionally follow
Response by Ashton Lewis.