Storage
Cigar mold vs plume
Mold is fuzzy, raised and patchy, often blue, green or gray, and it leaves a stain when you wipe it. Plume, if it is real, is a flat, even dust that brushes off clean.
What cigar mold looks like
Cigar mold is a fungus growing on the leaf, and it shows up as raised, fuzzy spots that can be white, gray, green, blue or yellow.
Look where air doesn't move. The foot. The cap. Seams in the wrapper. The spot where two cigars press together. Mold likes corners and contact points.
Then smell it. A humidor should smell of cedar and tobacco. Mold smells like a damp basement. If you open the lid and get musty before you get sweet, start looking.
Last clue: it spreads. One cigar this week, three next week. Plume, as described, doesn't move from cigar to cigar.
Is plume real?
Plume, also called bloom, is a fine whitish dust that some smokers say forms when oils in a well-aged cigar crystallize on the wrapper.
It's a popular story. It's also unproven. We looked for a published study that confirms plume's chemistry and didn't find one. Some smokers argue that most of what gets called plume is a light mold.
So here's our verdict. Treat plume as a claim, not a fact. If a seller tells you the dust on a cigar is plume and a sign of age, look closer anyway. When in doubt, call it mold.
Plume and mold, side by side
The wipe test separates most cases: plume is described as dry, flat and even, and mold is raised, patchy and leaves a mark.
| Check | Mold | Plume (as described) |
|---|---|---|
| Texture | Fuzzy, furry, raised | Flat, powdery, almost dry frost |
| Color | White, gray, green, blue or yellow | White to pale gray only |
| Pattern | Patches and spots | Even dusting over the wrapper |
| Where | Foot, cap, seams, contact points | All over, not clustered |
| Wipe test | Smears or leaves a stain | Brushes off, wrapper clean beneath |
| Smell | Musty, damp | No change |
| Over time | Spreads to neighbors | Stays put |
Pinholes and fine powder in the box are a different problem. That's insect damage, covered in our cigar beetle guide.
Mold needs water to grow
Mold grows when spores land on a damp surface, so too much humidity is almost always the cause in a humidor.
The EPA advises keeping indoor air below 60% relative humidity to prevent mold in a home. Cigars are kept wetter than that, around 65 to 70%. A humidor already lives near the edge. Push it a few points higher, add warmth and still air, and you've built a mold farm.
Common culprits: an overfilled sponge humidifier, a hygrometer reading low, a hot room in summer, a box packed so tight no air moves. Our 70/70 calculator shows how warmth changes the picture, and the humidity pack calculator sizes two-way packs that hold a set level.
It isn't just a storage problem. Researchers at Yunnan Agricultural University found that high heat and humidity drive mold on cigar leaf during curing, and that moldy leaf lost nitrogen, alkaloids and flavor compounds.
Found mold? Clean up in this order
Cleaning up mold means removing the affected cigars, fixing the humidity that caused it and drying the box out before it goes back in service.
- Pull the moldy cigars. Bag them and get them out of the room.
- Check every neighbor. Look at the foot, cap and seams of each cigar. Quarantine anything doubtful in a separate container.
- Empty the humidor. Everything out, trays and dividers too.
- Wipe it down and air it. Wipe the interior with a cloth barely damp with distilled water, then leave it open to dry fully. Skip bleach and sprays; cedar soaks up their smell.
- Test the hygrometer. A reading a few points low hides the problem. Calibrate or replace it.
- Re-season and restock. Bring the wood back up slowly with the seasoning method, then aim a few points lower than before.
If mold comes back after all that, the wood itself may be holding it. Some boxes aren't worth saving.
Can you smoke a cigar that had mold on it?
No one can tell you a moldy cigar is safe to smoke, and no cigar is safe to smoke in the first place.
The National Cancer Institute says there is no safe level of tobacco use. Mold adds its own problem: the Yunnan study notes some mold species produce toxins. And moldy leaf tastes worse anyway.
Our call is simple. Moldy cigar, trash. A cigar that sat next to one and looks clean goes into quarantine and gets watched for two weeks.
Mold and plume questions
Does plume mean a cigar is well aged?
Not reliably. Plume is said to form on long-aged cigars, but no published study we could find confirms what it is, so white dust is not proof of age.
Can mold spread to other cigars in the humidor?
Yes. Mold travels by spores, so pull the affected cigars straight away and check every cigar that touched them or sat nearby.
What humidity causes mold in a humidor?
There is no single cutoff. Risk climbs as humidity and temperature rise together, and a warm humidor drifting into the mid 70s RH is in the danger zone.
Is white dust on a cigar always mold?
No. It can be loose tobacco dust, or what some smokers call plume. Give it the wipe test and a close look: flat and even with no stain is less likely to be mold.
Research behind the mold advice
- A Brief Guide to Mold, Moisture and Your Home, U.S. Environmental Protection Agency
- Quality differences between healthy and moldy cigar tobacco leaves during air-curing, Frontiers in Microbiology (Yunnan Agricultural University)
- Cigar: storage temperature and humidity, Wikipedia
- Cigar Smoking and Cancer, National Cancer Institute