Cigar Mold vs Plume

Start with the practical answer, because you are probably holding the container: if you are unsure, treat it as mould. The cost of misidentifying mould as plume is a contaminated container and potentially a contaminated collection. The cost of misidentifying plume as mould is that you removed a few cigars you didn't have to. Those are not symmetrical, and the asymmetry should drive the decision.

The second thing to know is that the individual cigar is the less important question. Growth on a wrapper is a symptom of the container's conditions, and if you address the visible spots without addressing what produced them, you will be doing this again in a month.

The Four Tests

Work through these in order. Any single indicator can mislead; the pattern across all four is reliable.

1. Texture and profile. Plume, if it exists, is flat — a fine dust lying on the surface, sometimes described as crystalline, catching the light. Mould is three-dimensional: raised, fuzzy, hairy or velvety, standing proud of the wrapper. This is the single most useful discriminator. Look across the cigar at a low angle under good light rather than straight down.

2. Colour. Plume is white to pale grey, uniformly. Mould is often white too — which is why colour alone settles nothing — but any blue, green, yellow, orange or black tint is unambiguous. Coloured growth is mould, full stop.

3. Location and distribution. Plume appears evenly across the body of the wrapper and does not grow on the foot. Mould grows wherever conditions favour it: patchy, often concentrated at the foot or head, frequently worse on the side facing a humidification device or a container wall, and it spreads to neighbouring cigars.

4. Smell, then wipe — in that order. Mould carries a damp, musty, stale note distinct from tobacco. Plume is odourless. Then, gently, with a dry soft brush: plume brushes away cleanly leaving nothing behind. Mould smears, and leaves a stain where it was, because it has rooted into the leaf rather than resting on it.

Do the wipe test last. Once you disturb growth you have made spores airborne inside your storage, which is why the smell test comes first and why you should do any of this away from the open container.

An Honest Position on Plume

Most write-ups describe plume as a rare, desirable sign of good aging and leave it there. Taking a clearer position, because the hedging is what causes people to keep mould:

The mechanism is real and the sightings are mostly wrong. Oils and sugars migrating to the surface of well-aged tobacco and crystallising is chemically plausible, and it is what the term describes. But it is genuinely rare, it requires years of stable storage, and — this is the part usually omitted — early-stage white mould is visually near-identical to it at arm's length. A great deal of what collectors photograph and label plume is bloom or mould in its first days, before it has developed the fuzz that would give it away.

There is also a commercial incentive worth naming: "it's just plume" is a convenient thing for a seller to say about a spotted cigar. Treat the claim with the scepticism you would apply to any other seller-favourable diagnosis.

Practical consequence: the default assumption on white growth should be mould, revised only if all four tests point the other way. If your storage has not been stable at target for years, plume is not the likely explanation.

What to Do — Container First

1. Isolate the container. Close it and move it away from other storage before opening it again. Do not transfer anything into a clean humidor yet; that is how a local problem becomes a general one.
2. Inspect every cigar individually, not just the visibly affected ones. Work in good light, away from your other containers.
3. Remove affected inventory from the collection. Cigars with confirmed mould — rooted, staining, coloured, or musty — should be discarded rather than cleaned and returned. Mould that has penetrated the wrapper is not removable, and returning a marginal cigar to storage risks everything else in it.
4. Assess the unaffected ones. Cigars from an affected container that show nothing should be quarantined separately — a tupperdor with a pack rated at your target is ideal — and inspected weekly for a month before rejoining the main collection.
5. Strip and treat the container. Remove all trays, dividers and devices. Wipe interior cedar surfaces with a cloth dampened with distilled water only. No soap, no bleach, no vinegar, no alcohol — cedar absorbs all of them permanently and every subsequent cigar will carry the note. Then leave the box open in a dry, well-ventilated room, out of sunlight, for several days to a week.
6. Replace the humidification device outright. Foam and crystal media harbour mould in a way you cannot verify by looking. This is not the place to economise.
7. Re-season before reloading. An airing-out cycle leaves the lining dry. Treat it as new and run a full seasoning cycle.

Where growth has visibly penetrated the wood — dark staining, soft spots — the box itself is finished. Cedar that has hosted mould in its grain will reseed.

What Caused It

Mould needs moisture, warmth and still air. Storage produces it through some combination of:

• RH above roughly 72%, sustained. The most common single cause, and usually a device problem: an over-charged humidifier, free-standing water left in after seasoning, or a pack rated above the intended setpoint.
• Temperature above roughly 72°F, which lowers the humidity at which mould becomes viable. Warm and wet is the dangerous combination — see humidor temperature.
• No air circulation, which is what overfilling produces. Packed to capacity, the interior stops being one environment and develops damp pockets that a hygrometer in another corner never sees.
• Direct contact with a moisture source — a cigar touching a damp sponge or a saturated pack.
• An instrument that was lying to you. An uncalibrated hygrometer reading 6 points low means a box you believe is at 66% is actually at 72%. Growth appearing in a container that "read fine" is a classic sign the reading was the problem: calibrate the hygrometer.

Preventing a Recurrence

Store at the drier end of the range — 62–65% is materially safer than 70% and costs very little in enjoyment. Keep containers around 75% full. Verify instruments twice a year. Inspect quarterly rather than waiting to notice, and inspect new acquisitions before they join anything. Record the RH each container is actually holding, so a slow climb is visible as a trend rather than discovered as fuzz — the field set for that is in how to keep a cigar journal, and the broader failure patterns are collected in common storage mistakes.

FAQ

Is plume just mould? Frequently, yes — a large share of what gets called plume is early white mould or bloom. True plume, the surface crystallisation of oils on long-aged tobacco, is chemically plausible but genuinely rare and requires years of stable storage. Because early mould looks almost identical at a glance, the safe default on white growth is mould unless texture, colour, distribution, smell and the brush test all point elsewhere.

How can I tell if a cigar has mould? Mould is raised and fuzzy rather than flat, may carry blue, green, yellow or black tints, appears patchily and often at the foot, smells musty, and smears and stains when brushed instead of lifting away cleanly. Check texture at a low angle in good light before touching anything.

What causes mould in a humidor? Humidity sustained above roughly 72%, temperature above roughly 72°F, poor circulation from overfilling, direct contact with a wet device, or an uncalibrated hygrometer that has you storing wetter than you think. Usually more than one at once.

How do I clean a humidor after mould? Strip it, wipe the interior with distilled water only — never soap, bleach, vinegar or alcohol, all of which cedar absorbs permanently — then air it open in a dry ventilated room for several days. Replace the humidification device rather than cleaning it, and re-season the lining before reloading. Visible staining or soft spots in the wood mean the box should be retired.