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This is my second batch in a row where I've seen primary go for over two weeks. From my understanding, primary fermentation for an ale shouldn't take more than a couple of days (4-5 at most I believe). As of tonight, it is still bubbling maybe once an hour, but it is definitely still fermenting. When brewed, I used a yeast starter to increase the cell count, letting it set for approximately 20 hours before adding it to the wort.

Without further knowledge, I would guess I should let it complete no matter how long it takes, allow the diacetyl rest to finish, and then rack it, but this is at most, and uneducated guess.

As far as temperatures, it's been inconsistent. I don't have any method of temperature control past setting the thermostat of my place, and due to having guests over in the fall season who can not understand or appreciate the importance of regulating temperatures when it comes to brewing, I've had the thermostat set anywhere between 68 degrees Fahrenheit to 74.

My question is, what are the consequences for having it ferment this long? I've been told it's going to be dry, but past that, I don't know what I'm in for. Am I going to get a buttery flavor from the warm fermentation temperatures? Should I aim for the final gravity and just rack it to secondary? Should I let it go until days after it stops fermenting?

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The ongoing bubbling is just dissolved CO2 coming out of solution. -CamM (changed may to is)

That is why its still bubbling.

While I may be preaching to the choir, I just want to throw these out there.

The dryness will depend on your mash temps mainly, and any sugar additions that might have gone in to the wort. It is much harder for the yeast to munch on those the longer chain sugars, and they usually go dormant before they get to munch on them. That is unless you throw distillers yeast in there. :-P

So a quick sum up on mash, if you mashed higher, your wort will have more unfermentable dextrines, then if you mashed lower, which will produce more fermentable sugars.

For DME/LME you dont really have as much control over the sugars in your wort. This really depends on the DME/LME that you are using. If you are using extra light DME, I would assume its was a lower temp mash vs an amber DME or golden DME.

Those temp swings.... meh, it all depends on your yeast. Usually higher temps produce esters, which are the fruity flavors CamM was talking about. If CamM is getting green apples, that could also be Acetaldehyde in the beer. Not saying that is the case CamM, just pointing out stuff.

The other problem I could see at higher temps would be higher level alcohols. That is the hot alcoholic taste that comes with some booze. Though assuming your yeast wasn't a lager, I wouldn't worry about this too much. This can diminish with age.

Esters will also diminish if you age the beer longer. So if it tastes fruity and you dont like it, just let it sit longer.

Butter flavor comes from the chemical Diacetyl. This also imparts a slippery like mouthfeel.

"Diacetyl is produced during fermentation as a byproduct of valine synthesis, when yeast produces α-acetolactate, which escapes the cell and is spontaneously decarboxylated into diacetyl. The yeast then absorbs the diacetyl, and reduces the ketone groups to form acetoin and 2,3-butanediol, relatively flavorless compounds."

"Beer sometimes undergoes a "diacetyl rest", in which its temperature is raised slightly for two or three days after fermentation is complete, to allow the yeast to absorb the diacetyl it produced earlier in the fermentation cycle."

Usually that wont be a problem, but I think you should be safe from diacetyl, well depending on the yeast and style you were going for. Some yeasts give off more of the chemical.

Check gravity and rack it, the FG is not going to drop anymore. Again this depends on some factors, like yeast, style, and OG. Chances are the yeast just hit its attenuation mark.

Again, the beer is no longer fermenting, no need to wait.

Hope that helps.

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  • Thank you very much for all the clarification. I have a question though that I've been wondering about for some time, regarding the Diacetyl rest. I'm under the impression this will only happen in primary. Can this not occur once it's racked to secondary? Or is it just not as capable?
    – Scott
    Commented Nov 9, 2012 at 15:17
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    There is still some yeast that is being pulled over, but it tends to not be enough to absorb a lot of the diacetyl. In Primary, you have that great yeast bed that will work through filtering chemicals out of the wort.
    – Grico
    Commented Nov 9, 2012 at 15:56
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You will get fruity flavours (particularly green apple), from a warm ferment (source: brewing in Australia in summer without temp control).

I would start to test the gravity, if the SG is within the expected attenuation for the yeast (if you are not sure what that is for the yeast you used, 1.005 - 1.015 is the ballpark) and does not move for a couple of days, then your good to go.

(Also, the ongoing bubbling may just be dissolved CO2 coming out of solution.)

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    "the ongoing bubbling may just be dissolved CO2 coming out of solution" - Key phrase. Since you say it's only bubbling once an hour, I would bet that's just CO2 coming out of solution from temperature swings/sitting around. While you should not rely on bubbles to determine if fermentation is happening, it's probably done. Check the gravity.
    – fire.eagle
    Commented Nov 7, 2012 at 14:42
  • Huh. And I wasn't paying attention. Welcome to Homebrew.SE, CamM!
    – fire.eagle
    Commented Nov 7, 2012 at 20:19
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    if you have room, for your next batch, stick your fermenter in a bigger container with 3-6 inches of water. That will at least minimize temp swings, as it increases the thermal mass. Google 'swamp chiller' and take a stab at doing that. Even basic temp control will improve your beer DRAMATICALLY. (more so than quick chilling, moving to all-grain, and a dozen other things homebrewers typically do before getting temp control!) If you really want to be a nerd, do a simple temp control like above on half your next batch, and leave the other half to ferment ambient. you will taste the difference.
    – Pietro
    Commented Nov 8, 2012 at 15:12
  • Temp SWINGS have worse effects on beer than the 'WRONG' temperature.
    – Pietro
    Commented Nov 8, 2012 at 15:14
  • Thanks for the input! I'll definitely try swamp chilling on the next batch! My gravity reading read 1.011, so it's definitely done.
    – Scott
    Commented Nov 9, 2012 at 15:09
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You should be testing daily with hydrometer for gravity drops and tasting for beer flavors. racking to secondary will not cause a problem at this stage

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