Fault
Under-carbonation
A cider intended to sparkle that has little or no dissolved gas, usually because the bottle conditioning never started or the closure did not hold.
Also called flat sparkling cider, failed conditioning.
- Severity
- Quality — the drink is worse for it
- Where it starts
- Carbonation, Stabilisation, Packaging
- Can it be fixed?
- Yes, if caught in time
- When you notice it
- Carbonation, Packaging, Storage
- Signs
- 5 recorded
What it is
Under-carbonation is a cider that was meant to be sparkling and is not. It is a quality fault rather than a spoilage one, and its causes divide neatly into three: the yeast never fermented the priming sugar, there was not enough priming sugar to begin with, or the gas escaped through a closure that did not seal. Diagnosing which of the three applies is straightforward and determines whether anything can be done.
What you notice
Grouped by sense, because that is how the fault presents itself rather than how it works.
To hear
- Little or no hiss when the bottle is opened
To look at
- Cider that pours without a head and shows few bubbles in the glass
- No fresh sediment in the bottle after conditioning — A conditioned bottle should throw a light yeast deposit; its absence means fermentation never happened.
In the mouth
- A flat, slightly heavy mouthfeel in a cider whose balance assumed carbonation
How the batch behaves
- Some bottles from the batch carbonated and others flat — Points to closures or to uneven priming rather than to the yeast.
The words for it: Flat and lifeless. Each links to what produces it.
When it appears. Weeks after bottling, when the expected conditioning has not happened. It is one of the few faults where waiting longer is a legitimate first response.
It is among the small number of faults on this site with a genuinely reliable remedy, because the cider can usually be re-primed and re-closed. The window closes when the yeast population is no longer viable.
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739, Peter Mitchell / Cider and Perry Academy
What it is mistaken for, and how to tell
One observation per rival, chosen because it separates them rather than because it describes either. Several of these are not faults at all — a style feature, a normal outcome, or the fruit behaving as it does.
- Flat and lifeless — Under-carbonation is a gas problem alone; a flat cider is one whose acid and aroma have gone too. Adding gas fixes the first and does nothing for the second.
- A still cider — What was intended. Not every cider is meant to be carbonated, and several traditions are still by definition.
- A closure that has not sealed — Check for a wet ring under the cap or a crown that turns. A leaking closure loses gas continuously and is a packaging failure rather than a fermentation one.
What is actually happening
The chemistry or microbiology behind it. Understanding the mechanism is what makes the prevention make sense rather than being a list of rules.
Bottle conditioning depends on a viable yeast population fermenting a measured sugar addition in a sealed container. The gas produced dissolves into the cider until equilibrium is reached. If any of the three components is missing — viable yeast, sugar, or a seal — no carbonation results.
Viability is the commonest failure. A cider that has been filtered, fined heavily, cold-stabilised, sulphited, or racked repeatedly may have very few live cells left, and the population that remains has been sitting in ethanol with nothing to eat. Long ageing before bottling has the same effect.
The seal is the second. A crown cap crimped with a worn or wrongly sized crimper does not hold; a swing-top with a perished rubber gasket leaks slowly; a cork that was not driven fully home or that has dried in an upright bottle lets gas past. These failures are usually inconsistent across a batch, which is the diagnostic signature.
Temperature is the third factor. Yeast will not ferment priming sugar at cellar temperatures near freezing, and a batch conditioned in a cold store may simply be waiting rather than failed. Moving the bottles somewhere moderately warm often resolves what looked like a failure — subject to knowing how much sugar is in them.
How it happens
| Cause | Stage | How often |
|---|---|---|
| Too few viable yeast cells left in the cider at bottling | Carbonation | common |
| Cider filtered or fined before priming, removing the yeast | Stabilisation | common |
| Conditioning temperature too low for the yeast to work | Carbonation | common |
| Closures that do not seal — worn crimper, perished gaskets, poorly seated corks | Packaging | common |
| Priming sugar underweighed or unevenly distributed through the batch | Carbonation | occasional |
| Free sulphur dioxide high enough to suppress the conditioning yeast | Stabilisation | occasional |
Can it be put right?
Most cider faults cannot be reversed. Where that is the answer it is given plainly — an honest 'this batch is what it is' is more useful than a procedure that will not work.
| Option | Effectiveness | What it involves |
|---|---|---|
| Serve the cider as a still cider | Reliable | The uncomplicated answer. A well-made cider that failed to sparkle is still a sound drink, and reworking a whole batch is rarely worth it. |
| Move the bottles somewhere warmer and wait | Partial | The first thing to try where the cause may be temperature. Only do this knowing the priming sugar was correctly measured; warming bottles of unknown sugar content is how over-pressurisation happens. |
| Open, add a fresh yeast pitch, and recap | Partial | Practical for a small batch. The sugar is already in the bottle, so nothing further should be added beyond yeast, and fresh caps must be used. Laborious for anything more than a case or two. |
| Re-crimp bottles whose caps did not seal | Partial | Worth doing where the diagnosis is the closure, using a properly adjusted crimper and new caps. Cider that has already lost its gas will need reconditioning. |
| Add more priming sugar to bottles that are already sealed | Not possible | It cannot be done without opening them, and adding sugar to a batch whose actual content is uncertain risks over-pressurisation. Never do this. |
CiderHQ gives no additive dosage figures. An addition is a food-safety decision that depends on legal limits, on the juice in front of you and on what you are protecting against, and the right figure comes from your supplier’s or regulator’s own guidance rather than from a general reference.
Preventing it
- Bottle-condition while a healthy population is still present, or add a measured fresh yeast pitch at bottling as the supplier directs.
- Condition at a temperature the yeast can work at, and give it several weeks before concluding anything.
- Check the crimper and the caps on a test bottle before running a whole batch.
- Replace perished swing-top gaskets, and store cork-finished bottles on their side.
- Weigh the priming sugar and mix it evenly through the batch rather than adding it bottle by bottle.
- Keep sulphite modest where the cider is to be conditioned, since it works against the yeast you are relying on.
Under-carbonation is the least dangerous fault in this file and one of the most annoying, because the work has been done and the result is a cider that reads as unfinished. The diagnosis is unusually clean: look for sediment. A conditioned bottle throws a fine yeast deposit; if there is none, the yeast never worked, and the question is whether it was absent, cold or suppressed.
The most frequent underlying error is stabilising and conditioning at the same time. A cider that has been filtered bright, fined and sulphited is a cider that has had its conditioning yeast taken away from it, and priming such a cider without adding fresh yeast is asking a population that no longer exists to do a job.
The temptation the fault creates is the dangerous part. A maker looking at flat bottles naturally thinks about adding more sugar, and that is precisely the wrong instinct: the sugar is already there, and adding to an unknown quantity is how a batch ends up over-pressurised. If anything is to be added, it is yeast.
Patience is undervalued here. Bottle conditioning in a cold cellar is slow, and several weeks with no apparent change is normal rather than diagnostic. A batch judged failed after ten days is often a batch that had not started.
The compounds involved
Carbon dioxide
The other product of fermentation, which protects a cider from air while it is being made and, dissolved in the finished drink, changes both its texture and its perceived acidity.
Glucose
The sugar yeast takes first and the smallest of the three in apple juice, which is why the last sugar left in a slow ferment is almost never glucose.
Sucrose
The disaccharide of apple juice and the sugar most often added to it, split into glucose and fructose by the yeast’s own invertase before any of it is fermented.
Sulphur dioxide
The antimicrobial and antioxidant on which most modern cidermaking depends, and whose effectiveness collapses as pH rises — which makes every sulphiting decision a pH decision first.
The organisms involved
Saccharomyces cerevisiae
The yeast that finishes essentially every cider, whether it arrives in a sachet or from the fruit, the press and the vessel.
Saccharomyces bayanus
A name applied both to a hybrid *Saccharomyces* lineage and, loosely, to a whole class of commercial high-alcohol yeasts, and one of the least stable names in fermentation microbiology.
Where in the process it arises
Bottle conditioning
Carbonating cider by letting a second fermentation finish inside the sealed bottle, so the gas is generated where it is going to stay.
Priming
Adding a measured, calculable quantity of fermentable sugar at bottling so that the fermentation which follows generates a predictable volume of carbon dioxide.
Closure selection
Choosing between cork, crown, screwcap, cage and swing-top, a decision that fixes how much oxygen reaches the cider, whether it can hold pressure, and which faults it is exposed to.
Forced carbonation
Dissolving carbon dioxide into cider under pressure to a chosen level, giving complete control of the sparkle and none of the flavour a second fermentation would contribute.
Filtration
Passing cider through a porous medium to reach a stated visual brightness, at a real cost in colloidal material, body and aroma.
Bottling
Transferring finished cider into glass, where the dominant variable is how much oxygen the liquid picks up in the few seconds it takes to fill and close each bottle.
Faults it is confused with
These present similarly. What separates them is set out on each page.
Bottle over-carbonation
More dissolved carbon dioxide in the bottle than intended or than the glass is rated for — a presentation problem at the mild end and a physical hazard at the severe one.
Flat and lifeless
A cider with nothing obviously wrong and nothing to say: aroma faded, acidity dulled, finish short — usually the cumulative result of over-processing or slow oxidation.
Excessive sediment
More deposit in the bottle or vessel than the presentation intends, ranging from a normal conditioning yeast layer to a loose sludge that clouds every pour.
Where this comes up in a guide
The link lands on the step where the fault arises rather than at the top of the pathway, because that is where the decision that causes it is taken.
Carbonation: where the gas comes from and what it costs
How do I carbonate cider, and how do I do it without breaking bottles?
Diagnosing a batch that has gone wrong
Something is wrong with my cider. How do I work out what?
How cider is made, start to finish
How is cider actually made?
Planning a batch: fruit in, bottles out
How much fruit do I need, and how many bottles will I get?
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- Why did my cider bottles explode — Because fermentable sugar was still present, or too much priming sugar was used, and the pressure exceeded what the bottle could hold. Never bottle a cider whose gravity is still falling, and never use bottles not designed for pressure.
- Why is there sediment in the bottom of my cider bottle — In a bottle-conditioned cider the sediment is yeast and is expected — pour carefully and leave the last centimetre. In a filtered cider it means something has grown since bottling.
- Does cider contain sulphites — Most does. Sulphur dioxide is added to protect juice and finished cider, and fermentation itself produces a small amount even when none is added. European labels must declare it above 10 mg per litre.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- How is cider carbonated — Either by dissolving carbon dioxide into finished cider under pressure, or by letting a small second fermentation produce the gas inside a sealed bottle or tank. The first is faster and more repeatable; the second leaves sediment and a finer bead.
- How is sparkling cider made
Where to go next
- The fault finder — Describe what you can smell and see, and narrow it down from the signs.
- All faults — Grouped by where they come from and how serious they are.
- Cider science — The chemistry and microbiology these faults come out of.
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.
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.