Negative pressure first lager

Ok so I just recked into my secondary my first batch of lager, sat at about 50% had a nice ferment for about 10-12 days alot of action. Now less than 1 bubble a miute I racked into my secondary and to my surprise it has a negative pressure. It is pulling the airlock into the bottle. I emptied enough water so it wouldn't pull that into the bottle but I am still concerned about any air contaminates. I have never seen this before but I am not a master home brewer, Yet. any one have any ideas????

D-

Your beer is cooling down and contracting. As it does this it will create a suction. It is natural and nothing to get worked up about. RDWHAHB.

This surprised me the first time I saw it, also. Then I had a few college thermodynamics flashbacks and was reassured. Luckily for me, I had a homemade plastic tube-based fermentation lock rigged up (similar to a blowoff tube) because a regular fermentation lock wouldn't fit into the fridge. It drew the water from the "blowoff" vessel half the way up the tube!

You need to be careful and remember this little reality. The same thing happens if wort is not cooled enough after brewing. It will continue to cool and suck along the way. With an airlock you are generally OK, but is you use a blow-off tube that goes into a container of fluid, well, it can suck that fluid right up into your brew and, depending on what you have in the liquid, ruin your batch. YEARS ago I totally screwed a 15 gallon batch of Oktoberfest that way. Sooo, learn your lesson while it doesn't hurt.

It can also happen if the ferment is almost done and the air pressure increases because of a change in the weather. I see it a lot when I do a clearing step.

Well about an hour later it now is blowing off again. Thaks for the info I have never seen this before

Dmay said:

Ok so I just recked into my secondary my first batch of lager, sat at about 50% had a nice ferment for about 10-12 days alot of action. Now less than 1 bubble a miute I racked into my secondary and to my surprise it has a negative pressure. It is pulling the airlock into the bottle. I emptied enough water so it wouldn't pull that into the bottle but I am still concerned about any air contaminates. I have never seen this before but I am not a master home brewer, Yet. any one have any ideas????

D-

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This is one of the reasons I put cheap vodka in my airlocks. If any gets sucked back in, it just contributes to my abv %.