9 replies to this topic

[OhioMurb]

I brewed an IPA last week and was planning on racking to secondary this weekend so I could dry hop, but the krausen was still thick. It seemed wrong to move it until the krausen had dropped, but I didn't have a good answer why beyond "I've just always waited" So why do I wait for the krausen to drop? Is it a sign of positive pressure from the beer (ie gas still being released)? Is it a sign for one stage of fermentation ending? Or should I not worry? Airlock seemed done, 7 days is a reasonable time to expect this 1.066 beer to ferment, but I didn't take any measurements.

[Big Nake]

If in doubt, use your hydrometer. The yeast on the surface of the beer cannot really be used as a reference because some strains create big, puffy bubbles that sit on the surface for awhile after primary fermentation is complete. I typically never take a beer out of primary in 7 days. 2 weeks is normal (for ales) and part of that time may have been spent with the beer slightly warmer in case that particular strain of yeast created some flavors that I wanted cleaned up. So if the beer is done (and a hydro sample tells you), don't worry about the kraeusen on the surface. Cheers. Ps. What yeast? If US-05, I would agree that 7 days is okay, otherwise, maybe a few more days to make sure. Underattenuated beer tastes like dookie.

[OhioMurb]

All good points - I guess my question is what is happening when the krausen falls?

[Big Nake]

Well, when the yeast is done with its important work, it falls but some strains fall better than others. But falling krauesen doesn't necessarily mean that primary fermentaton is complete, but suggests that it's slowing down. I have used an English strain WLP023 Burton and it's really wild. It ferments and generally drops but it produces these huge, pillowy bubbles on the surface that stick around for awhile. When I used to ferment in glass I would see this and think that something was off. Anyway, for ales, I ferment low in the range (typically between 60 and 65°) and I let it go like that for 2 weeks or so and then get it a little warmer and let it go a few days or a week more. Nothing unsavory can happen to the beer during that extra time and you ensure that primary is done. It also keeps me from taking hydro samples because I assume that it's done at that point. * I probably shouldn't have said that I don't take hydro readings... my next batch will be underfermented! *

[SchwanzBrewer]

It depends. If you do an open fermentation you are supposed to rack the beer away before the krausen can fall and let bad stuff into your beer. For most homebrewers that isn't the case. The reason why you wait is because the yeast are not done. Even though the gravity might be at its lowest, the yeast still have work to do. Removing the beer from the krausen stunts the yeasts ability to clean up all the off flavor producing chemicals that were created during the main fermentation. Even though there might be enough yeast in suspension I think you ultimately risk changing the character of the beer because the top cropping ueast might not have a chance to do their part (not all yeast in a strain behave the same). So the general rule is leave it alone. Let the yeast do their jobs. 2 weeks in primary should do the trick. If it still looks like there is a krausen then either you have an infection or something like Ken said is going on. RDWHAHB. Cheers,Rich

[OhioMurb]

Schwanz - are you saying that there is something valuable in the krausen itself (proteins, etc?) or just that the krausen is a sign that the yeast is still working? ie is it the krausen itself that is valuable, or is it a sign of a valuable process?

[MakeMeHoppy]

I notice that some yeast leave a krausen that never seems to fall. After about a week I'll just swirl the beer in the carboy to collapse the krausen. Since you are dry hopping and keeping the beer at fermentation temps for that time I'd go ahead and transfer now. ( I normally just dry hop in primary)

[MtnBrewer]

I notice that some yeast leave a krausen that never seems to fall. After about a week I'll just swirl the beer in the carboy to collapse the krausen.

I was going to say the same thing. I'm not sure if it's the yeast or the beer itself but sometimes the krausen won't drop. Swirling the carboy will collapse the krausen. Then if it reforms, you'll know that there's still active fermentation going on, in which case you should wait to transfer. But as has been mentioned, when in doubt, use your hydrometer.

[SchwanzBrewer]

Schwanz - are you saying that there is something valuable in the krausen itself (proteins, etc?) or just that the krausen is a sign that the yeast is still working? ie is it the krausen itself that is valuable, or is it a sign of a valuable process?

Top cropping yeast.

[positiveContact]

I was going to say the same thing. I'm not sure if it's the yeast or the beer itself but sometimes the krausen won't drop. Swirling the carboy will collapse the krausen. Then if it reforms, you'll know that there's still active fermentation going on, in which case you should wait to transfer. But as has been mentioned, when in doubt, use your hydrometer.

I use the hydrometer and ignore the stuff on top and rack anyway. most stuff floating on the top sticks to the sides as the racking progresses.