How do you carbonate homemade cider?

Key facts

• Priming rate. PNW 621 says "A guide for sugar priming is about 4.0 g/l, which should produce about 1.0 atmospheric pressure (1.0 bar)". [1]
• Bottles. Use sturdy bottles, "preferably champagne type, which are rated for 6.0 bars". [1]
• Pressure risk. A University of Tennessee extension guide warns that in a closed container, "Gases given off during the fermentation process will cause an increase in pressure within the container, possibly resulting in the top blowing off or the container rupturing." [2]

What are the ways to carbonate cider?

1. Bottle priming. Add a measured amount of sugar to finished, dry cider just before bottling; the yeast turns it into carbon dioxide in the sealed bottle. This is the home version of the traditional method, and it needs live yeast, so "do not add additional sulfite to the cider after fermentation". [1]
2. Force carbonation. Inject food-grade carbon dioxide under pressure; at small scale this can be done with Cornelius kegs. Cool the cider to 30–36°F first, because carbon dioxide dissolves better when cold. [1]
3. Ancestral method. Bottle before the first fermentation has finished; it is hard to control at home, because nobody knows exactly how much sugar is left. See the glossary entry for ancestral method.

How do you bottle-prime cider, step by step?

1. Finish fermentation. Check with a hydrometer that the gravity has stopped falling (the same reading on several days in a row); see how long to ferment cider. PNW 621 says to know whether the cider still has fermentable sugar before priming. [1]
2. Measure the sugar. About 4 g per litre for around 1 bar; weigh it rather than guessing, and see how much sugar to add to cider for the gravity arithmetic. [1]
3. Bottle. Fill champagne-type bottles rated for 6 bar and close them with crown caps or wired corks; PNW 621 adds: "Do not exceed the maximum pressure that a given bottle can safely contain (see bottle specifications)." [1]
4. Condition. Keep the bottles at room temperature until they are carbonated, usually a few weeks, then chill them.
5. Open carefully. Open cold bottles pointed away from people; a gusher is a sign of over-carbonation, as explained in should cider have a head.

What can go wrong?

Bottles burst when the pressure inside is more than the bottle can take, usually because of too much priming sugar, priming a cider that was still fermenting, or a thin, non-pressure bottle. [1] [2] Store primed bottles in a box or closed cupboard away from people while they condition, and do not reuse thin bottles made for still drinks. For the whole process from apples to bottle, see how to make cider at home; to buy cider that is already sparkling, see where to buy sparkling cider.

Related answers: how to make cider at home · how much sugar to add to cider

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