I got an email asking how to add fizz to cider. Here is a (sort of) answer.
When the yeast is working it produces carbon dioxide which bubbles slowly to the surface. However if the cider is put into a pressurised container before the yeast has finished its work then the carbon dioxide diffuses into the cider where it stays until the pressure is released (the bottle is opened) and suddenly the bubbles rush to the top… ergo, fizzy cider.
Many cidermakers try and judge just how early to bottle their cider and get it wrong resulting in exploded bottles and sticky cider residue up the walls. This is why so many of us let the cider brew out fully to flat (no bubbles) scrumpy style cider before bottling.
There is another way to get fizz, and that is to inject CO2 into flat cider with a soda stream.. But frankly that is cheating and the big bubbles that produces are in my humble opinion a hindrance to the enjoyment.