I'm carbonating some mead I made in a 2 liter PET bottle with a carbonator cap. The bottle's been sitting in a fridge for the past week. Three times, I've found the bottle to be 'dented in' as if there's a vaccuum in it. I keep adding CO2 to it when I see this.
What would cause the dent? If the pressure was leaking out, the bottle would still retain its shape, wouldn't it?
Phil
It sounds as if the CO2 is going into solution and the pressure is not enough at the cooler temp to keep the bottle fully expanded. I assume it just barely dents in, not a huge collapse.
Cheers, Mike
The bottle's not collapsed, but there's a good dent in it. Can that much CO2 be absorbed into it? I've pressurized the three a couple of times? How could so much pressurized gas be absorbed as to cause a suction?
You can easily disolve many liters of CO2 into your mead, however, it will start to maintain pressure before that much is disolved.
Tom Veldhouse
But why would the bottle buckle? Once chilled, the mead and the air space (CO2 space) couldn't be less pressurized than it did when I last pressurized it, could it?
Phil
Sure, if you take a partly-filled and closed container of non-carbonated liquid, then purge the headspace with CO2, the gas will gradually dissolve into the liquid and create a lower pressure in the headspace. Depending on the temperature and the relative volume of the headspace versus the liquid, this equilibrium pressure can be less than atmospheric pressure, causing the soft bottle to collapse.
You can make it happen quickly. Partly fill the bottle with chilled liquid (maybe 4/5ths full), purge the headspace with CO2 at no more than a few psig, disconnect the gas, and shake.
You need a constant supply of CO2 at target pressure to prevent this.
Gases (and that includes CO2) are more soluble in cold liquid than in warm liquid. Try warming some Coke and see what happens! This is why it is better to pour champagne into a chilled glass....a warm glass only increases the foaming.
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