Remove air from bottle before putting cap on

Hi all,

I heard from somewhere on the Internet that oxygen in the headspace of bottles whilst bottle aging is a bad thing. For my next batch, I'm using PET bottles that are about 750mL in capacity.

Now, what I'm thinking is that I could fill each bottle up to a few centimeters below the top of the bottle (this is what I've read is the recommended headspace). If I then squeeze the bottle such that the beer level rises to the rim of the bottle and *then* put the cap on, there will be no air (and thus no oxygen) in the bottle. Obviously then carbon dioxide produced when the yeast ferments the priming sugars will fill the head space back up.

Has anyone tried this? It's not dangerous or anything is it, from an exploding bottle point of view? My only worry about doing it this way is that without the initial air in the headspace, there might not be enough pressure in there for a good carbonation to occur.

Your right, you need the head space for the beer to carbonate - what I do is let the bottle sit for about 30 seconds after filling with the cap on but not crimped. The theory being that CO2 coming out of solution from filling the bottle will push out O2

NovaAesa said:

Has anyone tried this? It's not dangerous or anything is it, from an exploding bottle point of view?

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Assuming there's no warping of the lip, I don't see why it would be any more dangerous than if you didn't squeeze the bottles beforehand. The bottle holds a certain amount of pressure and all you've done is reduced the amount of air pressure at the start. If anything, the bottle is less likely to explode.

My only worry about doing it this way is that without the initial air in the headspace, there might not be enough pressure in there for a good carbonation to occur.

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I wouldn't expect it to make too much of a difference. The little bit of space won't take much CO2 to fill.