My Airlock is Going Backwards

I've got a two piece airlock on my primary fermenter which contains an American Pale Ale. I'm about eight days in. Fermentation is slow. There is krausen (I had to pull out the airlock and peek since I use plastic buckets), but what is really interesting me is that there seems to be negative pressure within. Water is going up the bell shaped piece, approaching the entrance to the fermenter. I don't think that any water has gotten into the fermenter because the water level around the bell falls below the rim of the bell before the water within the bell can pour into the entrance. However, it seems very possible to me that outside air is getting in.

I am not worried about infection. I am a rebel. I am damn curious as to what is going on, though. Why would the pressure in the fermenter be lower than ambient? Global warming? Gremlins? I'll be racking to secondary tomorrow. Even if the phenomenon goes away, my perturbation will continue. Please, enlighten me!

Here's the recipe:
8 lbs Pale Malt
1 lb Vienna Malt
1 lb CaraHell Malt

Mash at 150F 1 hour; 1 qt. water/lb grain
Sparge 170F water; collect 6 gallons of sweet wort.

Boil: 60 minutes
Hops:
Nugget at 60 minutes
Perle at 15 minutes (add Irish moss and wort chiller)
Cascade at 2 minutes

Chill to <=80F, Pitch Wyeast 1056 (recovered from previous batch)

I managed to rack 4.5 gallons into the fermenter.

If you have enough head space... even a change in temp equal to a few degrees in that headspace will cause a vacuum. It happens.

also low atmos pressure when you put the airlock on followed by a high pressure system moving it can do it if the yeast hasn't taken hold yet. I had this happen to my once and I think the pressure different betweenthe two days was only like .15in

That's why I put cheap Vodka in my airlocks. I get a 1/2 gallon for 9 bucks and it will last years and protect many batches of beer from the dreaded IALSB (Infected Air Lock Suck Back). Nothing lives in it and if some gets sucked back, you just boosted your ABV a tiny bit.

I've seen this before where you can just drop a bit of cheap dime store vodka or rum in the airlock and things stay sweet and clean on the ferment.

Who else has done this?

-- Trev

Works great! Hate to waste ANY Vodka, but it is in the name of beer after all.

I use vodka now in the airlock. Back when I used waster, my winter warmer blew all the water out of the airlock and a guy at work suggested using vodka. I find that vodka is more stable in the airlock under strong fermentation (massive bubbling through the airlock). Water seems to be easily pushed out, whereas vodka will be pushed out but not entirely. If that makes sense? There's probably science behind it, like surface tension, miscibility or mass transfer? I don't know, but it works...

If you use clean distilled water and cover the airlock, there is little chance that anything will be able to grow in the water. But, if it is going to be there more than a week I use vodka.

The Pol said:

If you have enough head space... even a change in temp equal to a few degrees in that headspace will cause a vacuum. It happens.

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Changes in atmospheric pressure can cause quite a difference. 1 cm of water is equal to one millibar and atmospheric pressure can easily fluctuate +/- 10mb.

airlocks going backwards indicate that the temp in your fermenter is cooling and drawing the water in the other direction

It's the devil's work! Quick go get your exorcism kit!

I did not know the vodka trick but i think i will add it to my arsenal! Once again I learn something here every day!

Melana said:

I did not know the vodka trick but i think i will add it to my arsenal! Once again I learn something here every day!

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Ain't the Internet and HBT Great! They've changed my life!

Yeah! It also gives me an excuse to go to the store and see if there are any new beers in this week!!!
I love the internet!!!

Brilliant! (May have a shot meself, just to make sure the vodka's cheap enough!) -p

I use a blow off tube almost exclusively. It keeps me from having all of the problems associated with airlocks.