I'm in my first year making apple-cider from harvested apples.

The fermentation started 10 days ago. I let it bubble for 7 days and I filled some of clear juice it into a small bottle (using a Lightning type stopper) - just to see.

Yesterday evening I wanted to open the bottle to try. When flipping the stopper, 3/4 of the beverage spurted out. (I expected something like this and was outside). What was left was quite good, but didn't have any bubbles.

What did I do wrong? How to avoid these kind of explosions? How to stock cider into bottles correctly?

  • Have you measured gravity before bottling? If not, there is no way to be sure that fermentation was completed, and it will continue inside the bottle.
    – Philippe
    Sep 13, 2018 at 15:15

2 Answers 2


The problem is that the cider is still under active fermentation - even if it does not look it. The yeast is consuming sugar, producing CO2, alcohol and flavours. The CO2 gas is over-pressurising the bottles.

Bottling incomplete fermentation into glass can be dangerous!

The simple advice is to just wait, then bottle only when fermentation is complete. A small amount of sugar (or more juice) can be introduced into the cider at bottling time to provide just enough further fermentation for carbonation.

So how does one monitor the progress of the fermentation? There's a few devices to measure this. A "hydrometer" is a simple floating density meter. As the yeast consumes sugar and produces ethanol, the density of the liquid deceases (the density of ethanol is less than that of water).

When the changes in density stop for 3 days, and the stopping-point is at an appropriate finish, you can infer that fermentation is complete. Then it's OK to bottle. Side-Note: a poor fermentation can stop half-way, then restart later - say because of cold temperatures, that's why it has to be a reasonable stopping point too.

Failing this, in a PET bottle (i.e.: plastic soft-drink/soda bottle) bottle after 10 days, but then test for carbonation by squeezing the bottle. When it feels somewhat hard, put them in the fridge. This will slow the fermentation, not stop it. If left long enough, the PET bottles will still over-carbonate, even in the fridge.

  • I was wrongly assuming, that fermentation will stop, when the pressure has become too high. I have all the tools you're describing to observe the alcohol-level. I will try it out.
    – Patrick B.
    Sep 13, 2018 at 10:50
  • How much sugar would be needed per bottle/litre?
    – Patrick B.
    Sep 13, 2018 at 10:51
  • @Patrick - This site says 6-8 grams per litre - lovetobrew.co.uk/batch-priming-25-w.asp
    – Kingsley
    Sep 14, 2018 at 1:23

I think you need to wait for fermentation to stop before you bottle it, as co2 is being produced in the bottle and builds up the gas inside. Once fermentation has stopped you can filter it and you will have a still cider. If you want fizzy cider you can add a very small amount of yeast to the bottle but I guess you may need to experiment with that.

  • 3
    You need to add a bit of sugar to the bottle, so that the yeast that's still in suspension can create CO2.
    – Robert
    Sep 12, 2018 at 16:28

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