I am making a cider using 1.5L apple juice, 1 cup sugar and Saflager s-23 Dry larger yeast.

I was using a balloon with a pin hole as the "air lock" on this as all my air locks were being used.

It had pressure for two weeks then seemed to die down a bit. When it died down I had a taste and it was slightly sour and yeasty so I put a new balloon on it and left it. I did not put a pin hole on this one and the balloon is now being sucked into the carboy.

What has cause this inward pressure and what does it mean for my cider?

I am going to move it to a bottle now and cap it and let it sit for a month or so. Is it worth doing this or is it buggered?

  • maybe you've made dark-matter? how forcefully is it being sucked into the carboy?
    – dax
    Oct 30, 2013 at 12:11
  • good thing you used a balloon and not a normal airlock, think of all the water and outside air that would be getting sucked in right now!
    – pjreddie
    Oct 30, 2013 at 14:03
  • pjreddie - that happens whenever you use an airlock - a small amount of air is pushed through the airlock when the atmospheric pressure increases. The liquid will remain in the airlock, unless it's overfilled.
    – mdma
    Oct 30, 2013 at 16:03
  • @dax are you taking the piss with dark-matter? Sounds like it should be from a star wars movie?
    – WillNZ
    Oct 30, 2013 at 19:52
  • 1
    @WillNZ, definitely taking the piss :)
    – dax
    Oct 31, 2013 at 9:44

1 Answer 1


The inward pressure is caused by the temperature of the air in the carboy being colder than the air outside and/or increases in atmospheric pressure - both will cause the pressure inside the carboy to be less than the pressure outside.

This doesn't indicate that there is anything wrong with your brew.

  • Should I now move the cider to a bottle and let it sit or leave it in the fermenter?
    – WillNZ
    Oct 30, 2013 at 19:46
  • 1
    You can bottle it now. Next time, you only need to use a fraction of the s-23 yeast - around 1/5 of the packet at most. A whole packet to 1.5l of cider is way too much, which is probably why it tasted yeasty. If you can put the cider in the fridge, that will help the yeast settle to the bottom. (This is known as cold-crashing.)
    – mdma
    Oct 30, 2013 at 20:19
  • thanks for the advice. I used half of the packet of the yeast. Sorry I should have mentioned before. I will cold crash it and see how it goes
    – WillNZ
    Oct 30, 2013 at 20:26
  • how long should the cold crash process be? I have a 1.5L Grolsh bottle that I have put the cider in but it is too large for my fridge. It has been in there for 2days at a very cold temperature. Will the process have worked now and can I take the bottle out of the fridge for cupboard storage?
    – WillNZ
    Nov 3, 2013 at 2:51
  • yes, that's plenty of time - if possible you should siphon the cider to another container, otherwise any movement will simply stir up the sediment again.
    – mdma
    Nov 3, 2013 at 16:31

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