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Making guide

Carbonation: where the gas comes from and what it costs

How do I carbonate cider, and how do I do it without breaking bottles?

In short

Carbon dioxide dissolves into cider under pressure and comes out of it when the pressure drops. Everything else follows from that one relationship: how much gas a cider already holds depends on how cold it is, how much more you can add depends on what the container will hold, and the pressure a sealed bottle reaches depends on the warmest place it ever sits — not the cellar it normally sits in.

There are two routes. Fermentation makes the gas in the sealed container, from sugar the cider already had or from sugar you added; or you dissolve gas from a cylinder before filling. The first is cheap, slow, leaves a deposit and is a fermentation you cannot see. The second is fast, needs equipment and leaves nothing behind.

This is the one part of cider-making with a mechanism for serious injury, and the injuries come from arithmetic rather than from carelessness. Glass rated for pressure fails abruptly rather than progressively: it is either inside its rating or it is not, and there is no warning in between.

Who this is for. Anybody putting cider into a sealed container with the intention of it being fizzy, or worried that a batch already in bottles is doing something it should not. It assumes a finished cider and a hydrometer; the making comes earlier. (assumes some experience · 7 steps)

Worth reading first
Where scale changes the answer

The physics is the same at every scale and the consequences are not. A domestic batch is a crate; a commercial one is a pallet, and a pallet that has been standing in a warm loading bay is a different order of hazard. Above hobby scale the answer is usually a pressure-rated tank and counter-pressure filling rather than a bigger crate, and closure specifications stop being a rule of thumb and become a supplier’s figure.

Four ways to make cider sparkleBottle conditioning, tank conditioning, the traditional method and forced carbonation, each shown as the three steps that define it.Bottle conditioningadd sugarseal andkeep warmsedimentstays inTank conditioningfinish ina tankhold thepressurefilter, thenfillTraditional methodadd sugarferment inthe bottleriddle anddisgorgeForced carbonationchill itinject CO₂fill underpressureOnly the first leaves sediment in the bottle
Bottle conditioning, tank conditioning, the traditional method and forced carbonation, each shown as the three steps that define it.
Described in full
Layout
Four rows, one per method, each broken into three steps read left to right. The steps are what distinguishes the methods; the finished gas level can be identical.
Bottle conditioning
A measured sugar addition, then sealing, then a warm rest while the remaining yeast ferments it. The gas has nowhere to go but into solution. Yeast sediment stays in the bottle, so the cider is cloudy if poured carelessly.
Tank conditioning
The same refermentation done in a sealed pressure tank rather than in each bottle. The tank holds the gas, the cider can then be filtered clear, and it is filled into bottles under counter-pressure so nothing is lost.
Traditional method
Bottle conditioning followed by riddling and disgorging: the sediment is worked into the neck, the neck frozen, and the plug of ice expelled. The result is bottle-fermented and brilliantly clear, at the cost of a great deal of handling.
Forced carbonation
No fermentation at all. The cider is chilled, carbon dioxide is injected until it dissolves to the target, and it is filled under pressure. Fast, exactly repeatable, and the only method that lets gas level be chosen independently of everything else.
What differs in the glass
Conditioned ciders carry finer, more persistent bubbles and a trace of yeast character; forced carbonation gives a coarser bead that dissipates faster. The difference is real but smaller than the difference between two ciders.
The sediment question
Only bottle conditioning leaves sediment in the bottle as a matter of course. Whether that counts as a flaw or as evidence of method depends entirely on the tradition being judged against.

The path

Each step says what happens, why it matters downstream, and what you are actually deciding. The links under a step are where the depth is.

  1. 1. What "carbonation" is actually measuring

    Carbonation is quoted in volumes: the volume of carbon dioxide gas, measured at standard temperature and pressure, dissolved in one volume of liquid. A cider at 2.5 volumes holds two and a half litres of gas in every litre of cider. Still cider sits near 0.8–1.0, a light prickle around 1.8, an ordinary sparkling cider around 2.5–3.0, and traditional-method products above 3.5.

    The gas is not sitting in the headspace waiting to be released. It is in solution, and how much stays in solution is set by Henry’s law: dissolved concentration is proportional to the partial pressure of the gas above the liquid. Raise the pressure and more dissolves; drop it and the excess comes out, which is what a pour is.

    Everything practical follows from that. It is why a warm bottle is at higher pressure than a cold one holding the same gas, why a cider poured from a height loses its condition, and why the number a maker chooses at bottling is not the number the bottle experiences in August.

    Why it matters: Every figure downstream — priming sugar, bottle pressure, closure choice — is a consequence of this one relationship, and a maker who has not understood it is working from tables rather than from a model.

    What to measure

    • The carbonation level you are aiming at, in volumes — What the cider will feel like, and which containers are admissible. It is the input to everything else here. Work it out.

    Tools for this step

    Go deeper

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • The Science of Cidermaking and associated technical writing

      Andrew Lea · reference work · passage verified 2026-08-24

      Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

  2. 2. The cider already holds gas, and how much depends on its temperature

    A cider that has finished fermenting under an airlock is not flat. Fermentation produced carbon dioxide continuously and the liquid has been sitting under a blanket of it at roughly atmospheric pressure, so it holds whatever will dissolve at that pressure and that temperature — around 1.7 volumes at 0 °C, about 0.86 at 20 °C, and less as it gets warmer.

    That residual is the single most-skipped input in priming, and skipping it is how a target of two and a half volumes becomes four. A cider racked cold still holds the gas the cold gave it, and adding priming sugar as though it held none adds a second full charge on top.

    It also has to have equilibrated. A cider moved from a cold store an hour ago is still holding the cold store’s gas, whatever the thermometer on the wall now says. Use the temperature it has actually been sitting at.

    Why it matters: This is arithmetic that decides whether glass holds. Ignoring residual gas is the commonest single error behind over-pressurised bottles at domestic scale.

    Take care here

    Priming a cold cider as though it were uncarbonated roughly doubles the result. A cider at 2 °C already holds about 1.6 volumes — most of a pétillant carbonation — and a full priming charge on top of that will take an ordinary bottle past what it can hold. Take the temperature reading before the sugar calculation, not after.

    What to measure

    • The temperature the cider has been sitting at, in the liquid — How much dissolved CO₂ it already carries, and therefore how much of your target is already met. Not the room — the liquid, after it has settled. Work it out.

    What can go wrong here

    Tools for this step

    Go deeper

    • Priming sugar — The calculation with the residual gas accounted for, which most priming calculators omit.
    • Cold maturation — Why a cider is often cold at exactly the moment somebody wants to bottle it.

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

    • Cider and perry production technical training material

      Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject

      Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.

  3. 3. Three routes, and what each commits you to

    *Natural conditioning.* Bottle before fermentation has quite finished, and the sugar still present carries on working in the sealed bottle. This is how a great deal of traditional French and Spanish cider is made, and it is the least controllable route: the amount of gas depends on how much sugar was left, which is a number nobody measured. Traditional practice manages the risk with heavy glass and cellar temperatures rather than with arithmetic.

    *Priming.* Ferment to dryness, confirm a stable gravity, then add a measured sugar and seal. The yeast still in the cider consumes it and the gas has nowhere to go. This is controllable, cheap, slow — weeks rather than hours — and it leaves a deposit, because the fermentation happens in the bottle.

    *Forced carbonation.* Dissolve gas from a cylinder into the finished cider under pressure, then fill under counter-pressure so it does not foam out. Fast, repeatable, leaves no sediment and needs equipment: a gas supply, a way of holding pressure, and a filler that can work against it.

    The route is legible in the glass afterwards. A fine, persistent bead points at a slow secondary fermentation; a coarse one that collapses points at forced gas. A deposit means conditioning happened in that bottle; no deposit means it did not, or that the bottle was disgorged.

    Why it matters: The three differ in cost, in control and in what they leave behind, and the choice is made before bottling rather than after.

    Hazard

    Natural conditioning is the traditional route and it is the one with no arithmetic behind it: the gas comes from however much sugar happened to be left, which is a quantity nobody measured. Traditional practice manages that with heavy glass and a cool cellar, not with a calculation, and both parts of that are load-bearing. If you take this route, use bottles rated for well above what you expect and store them somewhere that does not get warm — because the ceiling is set by the residual sugar rather than by your intention.

    What you are deciding

    • Whether you can confirm the ferment has finished. If not, priming is not available to you and natural conditioning is a gamble with the glass.
    • Whether a deposit is acceptable. It is expected in a bottle-conditioned cider and is not a fault; it is also a thing to pour around.
    • Whether you have pressure-capable equipment. Forcing without counter-pressure filling loses most of the gas at the filler.

    Tools for this step

    Go deeper

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

    • Cider and perry production technical training material

      Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject

      Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.

  4. 4. Priming: the arithmetic, and the assumption it rests on

    Sugar ferments to roughly equal masses of ethanol and carbon dioxide, and the stoichiometry is exact enough to calculate from: a gram of sucrose yields about 0.51 g of CO₂, dextrose monohydrate about 0.44 g. One volume of CO₂ is 1.96 g per litre. So the sugar needed is the gas still wanted, converted through those two constants.

    The assumption underneath is the whole risk. The calculation assumes fermentation has genuinely finished, so that the only sugar fermenting in the bottle is the sugar you put there. Prime a cider that still has sugar to go and the two charges add, and the result is far outside what the glass will hold.

    Confirming that is not a matter of judgement. Two hydrometer readings several days apart, unchanged, is the evidence. Airlock activity is not: an airlock bubbles from a change in room temperature alone, and a slow ferment can produce gas too gently to see.

    Why it matters: Priming an unfinished cider is the single mechanism behind most burst bottles, and the check that prevents it takes four days and costs nothing.

    Hazard

    Confirm a stable gravity before priming anything. Priming a cider that has not finished adds a measured charge on top of an unmeasured one, and the result can be several times the intended pressure. A sweetened cider is the same problem in a more obvious form: sugar plus live yeast in a sealed container is a fermentation nobody is watching. Either stabilise it or accept that it will carbonate to whatever the remaining sugar allows.

    What to measure

    • Two specific gravity readings, several days apart — Whether fermentation has finished. This is the reading the whole priming calculation assumes, and the only one that can confirm it. Work it out.
    • Priming sugar for the target, at the cider’s current temperature — How much to add, with the gas already dissolved subtracted. Work it out.

    Go deeper

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

    • Cider and perry production technical training material

      Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject

      Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.

  5. 5. The pressure that results, and what the glass will hold

    A given carbonation reaches a given pressure at a given temperature, and the temperature matters more than people expect. An ordinary sparkling cider at 2.8 volumes sits around 2.3 bar in a 20 °C cellar. The same bottle at 30 °C is near 3.3 bar, and at 40 °C — a shed or a car in summer — around 4.5.

    Against that: a crown-capped beer bottle is generally rated to roughly 4 bar. A Champagne bottle is rated far higher and is the domestic answer for anything above about 3 volumes. A still-wine bottle is not a pressure vessel at all and a swing-top is a closure rather than a rating.

    So the figure that decides the container is not the pressure at bottling and not the pressure in the cellar. It is the pressure at the warmest temperature the bottles will ever reach, including the summer after next, including transport, including the week somebody moved the crate.

    Prediction here is indicative rather than exact. The relationship is well established; the condition of an individual bottle is not, and that is what actually fails. Treat the number as the order of magnitude of the risk.

    Why it matters: Over-carbonated bottles fail in summer rather than in winter, and the arithmetic that would have shown it is available months earlier.

    Hazard

    Glass rated for pressure fails abruptly rather than progressively, and it fails by fragmenting. Use Champagne bottles with a crown cap or a caged cork for anything above about 3 volumes; store conditioning bottles cool and in a closed crate; and if a bottle bulges, weeps or gushes, chill it first, do not shake or invert it, and vent it behind a barrier with eye protection and the neck pointed away from you and from anybody else.

    What to measure

    • Pressure at the warmest storage temperature, not the current one — Whether the closure and the glass will hold. This is the number that decides the container. Work it out.

    What can go wrong here

    Tools for this step

    Go deeper

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • Cider and perry production technical training material

      Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject

      Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

  6. 6. Headspace, oxygen and what else is in the bottle

    The space above the cider is not empty and it is not neutral. Air trapped at filling brings oxygen, which the cider will consume over months into the aldehydes that read as sherry and cardboard — so a generous headspace is an oxidation problem as well as a pressure one.

    It is a pressure variable too, and in the unhelpful direction: a smaller headspace means the gas produced by conditioning has less room, so the pressure rises further for the same sugar. The two considerations pull the same way at domestic scale, which is convenient: fill consistently, leave a small and even headspace, and both problems shrink.

    A conditioned bottle also contains live yeast, which is why it can keep changing. That is the point in a bottle-conditioned cider and a hazard in a sweetened one, and the difference is whether there is anything left for the yeast to eat.

    Why it matters: Headspace is set once at filling and cannot be revisited, and it decides both how the cider ages and how much pressure the same priming charge produces.

    Take care here

    Headspace works against you on pressure as well as on oxidation. The same priming charge in a bottle filled low has less room to expand into, so it reaches a higher pressure than the calculation — which assumes a normal fill — predicted. Fill consistently, and treat an unusually low fill as a bottle to open first and chilled.

    Go deeper

    • Bottling — Filling without picking up oxygen, which is most of the skill.
    • Topping up — The same problem before the bottle, where it does most of its damage.
    • Oxidation — What the trapped air becomes, and why it cannot be reversed.

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • The Science of Cidermaking and associated technical writing

      Andrew Lea · reference work · passage verified 2026-08-24

      Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.

    • The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers

      Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25

      Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.

  7. 7. When it has gone wrong

    *Too little.* A conditioned bottle that is flat after a month is usually a yeast problem rather than a sugar one: the population was too depleted, too cold, or removed by filtering before priming. Warmth and time fix some cases; re-priming with a fresh yeast fixes more. This is one of the few faults on this site with a genuinely reliable remedy.

    *Too much.* Bulging caps, weeping closures, a bottle that gushes on opening or hisses far longer than its neighbours. Chill the whole batch immediately, which lowers the pressure substantially, move them crated rather than by the neck, and keep them out of any warm room while you work out which of the two causes it was.

    *Uneven across the batch.* Bottle conditioning is a per-bottle fermentation, so some variation is inherent. Large variation points at the priming sugar not having been mixed evenly through the cider before filling, which is a mechanical problem with an obvious fix next time and no fix now.

    *Gas but no life.* A cider can be correctly carbonated and still read as flat, because carbonation is not the only thing that makes a drink lively. If the acid and the aroma have gone, adding gas produces a fizzy tired cider.

    Why it matters: Three of these four have remedies and one does not, and telling them apart takes an observation rather than a guess.

    Hazard

    Do not warm a suspect bottle to make it easier to open, and do not open one at room temperature to check. Chilling is both the safety measure and the diagnostic: a bottle that still gushes cold has a genuine problem, and one that does not was simply warm.

    Tools for this step

    Go deeper

    Sources

    What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

    • Cider and perry production technical training material

      Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject

      Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.

    • The Science of Cidermaking and associated technical writing

      Andrew Lea · reference work · passage verified 2026-08-24

      Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.

Where to go next

Guides that follow on from this one.

Questions this answers

Shown so you can tell whether this is the guide you wanted.

Where to go next

Sources

What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.