I have three batches aging in gallon jugs under bubbler airlocks. Two have what I call positive pressure, ie. more pressure inside the jug than outside, but one had negative pressure, that is it was trying to draw the water into the jug. I would suspect an environmental change if all three showed this condition but don't have a clue why this one batch is acting this way. When I racked this batch three weeks ago it had dropped to 1.000sg (down from 1.100) and until this morning everything was normal. Any ideas on what is happening?
Negative pressure in airlock
Mar 04, 2006
3 Replies
It may be a temperature change! If the wine was racked high and now the temp dropped, a vacuum will occur in the jugs as the wine contracts pulling water from the air lock into the wine. Remove the air locks carefully as the water in the lock will be sucked into the wine, stopper and all, reinsert stopper, pressurer should be equalized now.
Also look at the amount of headspace. Air will contract/expand differently than wine.
Andy
Lots of things can cause this sort of effect. First, a drop in temperature is the primary cause. But why would one show it and others not? Okay, if there is any fermentation of any type in the carboy it will keep the pressure positive. If one carboy quits and the other is still slowly fermenting this would explain it. Also, if all carboys have quit fermenting but one has less dissolved CO2 than the others, it will show the effect more. You have probably heard of degassing. Well if one of the carboy has already lost it's gas and the others have not, if the pressure drops in the atmosphere, the dissolved gas will come out of solution keeping the pressure up. As you can see, there are a lot of factors, none of them a problem. I am sure others can think of other things that would/could cause this.
Ray
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