Brewed a Munich Helles yesterday and fermented it with an ale yeast. OG was 1.040 and it's in my fermentation fridge at 68f. Today when I checked it the lid was domed but the airlock wasn't bubbling. Assuming it was clogged, i,removed, cleaned and replaced it.
After watching for 10 mins and seeing a LOT of krausen coming through the airlock, I switched over to a blow off tube. While there is some obvious activity in the tube, there is still a buildup of krausen and the lid seems still ready to pop.

What's happening? The only way I can get the lid down is to pull the tube and push krausen out through the hole.

  • What size blow-off tube are you using? I use a 1" ID, which fits into the neck of my carboy, and there's no way that will block.
    – jalynn2
    Commented May 19, 2014 at 16:59

2 Answers 2


The Krausen shouldn't be so thick that it blocks the blow off tube causing the fermenter to explode.

Is it possible to put on a lid with a bigger hole in it so there is more room for the Krausen to pass through?

If not then I would keep doing what you are doing and clean out the gap every now and again. Remember when you clean it out you should sterilize it so that is doesn't get an infection.

You could also try to put some weight on the lid so that it doesn't bulge out and is forced to go through the blow off tube(but I would monitor this regularly).

  • 1
    Thanks. Been monitoring closely. It seems to have slowed down a bit is I think we'll make it.
    – uSlackr
    Commented May 19, 2014 at 1:41
  • 1
    I can't wait to remove the lid to see how thick the krausen is on this. And not I need to pick up a larger dia. hose for future challenges!
    – uSlackr
    Commented May 23, 2014 at 16:45

I'd just remove the lid and set it lightly on top, or cover the fermenter with foil or plastic wrap. Many breweries use open fermentation. Your will have a loose covering and the krausen will protect the beer. Resecure the lid once the krausen drops.

  • I'd second this. Contamination typically happens when particulate falls in from above (this isnt specific to beer), so loosely covering it should be fine until the fermentation slows.
    – STW
    Commented Jun 11, 2014 at 3:19

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