It is my understanding that if one is fermenting (primary) with a bucket with a plain lid on it that it is necessary to leave a small gap (i.e. to leave the lid open a bit)

Is this an adequate solution to help fermentation and is there any other way I can avoid the contamination of the beer during fermentation?


Sure, you can do an open ferment with the bucket lid partially open. Be certain to pitch plenty of yeast, and airate the wort - you want a short lag time before the yeast start fermenting, to ensure no other microbes take over the wort.

Once fermentation has started, the co2 produced will keep airbourne microbes out of the fermentor.

For a normal gravity beer, under 1060, bottle after 2 weeks to avoid the chance of oxidizing the beer. During fermentation, the beer is protected by a layer of co2, but after the co2 stops being produced, the open ferment allows that layer to dissipate and be replaced with air.



Are you saying your lid has no hole for an airlock? You definitely need some way for gasses to escape, but leaving the lid partially open sounds pretty dangerous.

Would it be possible to make a hole in the lid so you could use an airlock/blow-off tube?

  • It would be possible to put a hole in it I guess. Would a blow off tube be a simple tube (the kind you would use for siphoning) or a more specified piece of equipment? Mar 19 '12 at 15:36
  • Drill a 1/2 inch hole. At my LHBS a plastic airlock goes for $1.99.
    – bk0
    Mar 19 '12 at 15:43
  • He'll need a rubber gasket as well, or some way to seal it. @Danger: Yes, a simple tube, placed into a container of sanitizer/bleach water will do fine. I recommend a blow-off tube in general, so that if the yeast overflow your container, you don't have as big of a mess to clean up. Mar 27 '12 at 20:21

If your santitation is spot on, you can certainly ferment in a bucket and just cover it with some foil. This would be akin to an open fermentation. The foil would simply keep stuff from falling into it from the air.


I ferment open quite often with no problems encountered. There are plenty of breweries who still ferment open. I often leave the lid off completely, but if you are paranoid just don't press it down to seal. Just put it on top and the gases will escape. After fermentation is over, and it starts settling, I usually rack it to a carboy or seal it up. I use an airlock for this stage, but I don't think you will have an issue with the above. Make sure that there is no way for fruit flies to get in though, or you may end up with five gallons of vinegar. And try to keep the air out once the fermentation starts to slow. You could seal the bucket and vent every so often so you don't end up with a bunch of pressure buildup.

  • Man, my kitchen crawls with fruit flies this time of year if I leave any dishes or water in the sink. I created a fruit fly trap with a jar of vinegar and a plastic baggie with a hole cut in it over the jar.
    – Graham
    Mar 27 '12 at 12:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.