Airlock's Little Plastic Cap

Today is brew day, and I have somehow misplaced the little plastic cap for my 1 piece, s shaped airlock. Can I leave the top of the airlock exposed, or should I cover it some other way? Thanks!
(Northern Brewer Chinook IPA etract, by the way.)

Probably fine to leave it open. If it worries you, put some aluminum foil on it and poke some small holes in it.

I got a pretty quick evaporation without one. I'd find a replacement or risk running dry at some point.

Take a square of plastic off the packaging to a loaf of bread and sanitize it (or Saran wrap). Rubber band it around the top and poke some holes it in.

I used that setup without holes to block my airlock on a carboy cap setup and shift the CO2 flow to the blowoff tube. It was starting to look like a science project volcano out both ends.

^^ Aluminum seems to oxidize/'rust' with the alcohol vapor. It eats away the oxide. I guess that depends what's in the airlock; I use vodka.


Alternately, maybe put a marble in that top part. I'll try that out now. The CO2 will displace it gently.

Thanks, guys! I have unused Mr. Beer plastic bottle caps that would easily fit over the top without falling off. I'll poke a few holes in the top of that, then sanitize.

I recently purposely left mine off for fear of blow-off, and additionally only added about 1/3 of the water to the 'Max Fill' line. No problems on either account - missing lid was no problem and the water would have taken a week or more to evaporate at in the mid-60s. I think the lid will keep fruit flies and other bugs from crawling in but otherwise is not necessary (that's the wonderful thing about S-locks - the lids don't affect the functionality of the airlock itself).

On a separate occasion, I used the lid with 1/3 water fermenting a saison at around 90 degrees. I DID run into the evaporation issue there, but the solution was to just add another tsp of water - problem solved.

If you're worried, then you can certainly put a small patch of aluminum foil over the top to loosely seal it.

do you have any kids balloons, where you can stretch one over the top of the airlock?

dadshomebrewing said:

do you have any kids balloons, where you can stretch one over the top of the airlock?

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No, no balloons. But if the Mr. Beer cap doesn't look stable, I'll try the aluminum foil/rubberband method. Thanks again everyone!

Saran wrap works great. No reason to think that the beer cap won't work. Just keep an eye on the water in the airlock and top off as necessary.

No issue for a few weeks. Cover loosely with a little foil if you really are concerned.

I'd sanitize a piece of tin foil and rubber band it on. It won't be air tight so you won't need to poke holes. And as a matter of fact if you every don't have an air lock you can just do this on the fermenter. In fact that's how I air lock my starters on my flasks.

stpug said:

I think the lid will keep fruit flies and other bugs from crawling in

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No, no it won't.

Thank goodness that vodka kills ants.

My basement is full of spiders. I was propping up a fermentation bucket with my hands during a tricky transfer operation (last time I'm using an autosiphon) and they started crawling out from the recesses around the cover.

Arrheinous said:

My basement is full of spiders. I was propping up a fermentation bucket with my hands during a tricky transfer operation (last time I'm using an autosiphon) and they started crawling out from the recesses around the cover.

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Oh good. I'm just about to go to bed. At least I'll know where my nightmare tonight came from.