A humidor is only a box until something inside it adds moisture and something tells you how much is there. This chapter of Cigars 101 covers both halves: the humidifier that keeps the air at the right relative humidity, and the hygrometer that measures it. For the box itself, see humidor storage and the humidor buying guide. For preparing a new cedar box before any of this, see how to season a humidor.
What you are trying to do
The goal is a steady reading somewhere in the commonly recommended range of about 65% to 72% RH, at a moderate room temperature. Steady matters more than the exact number. Cigars that swing between damp and dry can crack, burn unevenly, and taste harsh, even if the average reading looks fine.
Every humidor slowly loses moisture through its seal and to the room, and every time you open the lid. A humidifier replaces that lost moisture. The better ones also soak up extra moisture when the reading climbs too high.
One-way and two-way humidification
A plain sponge or a dish of water is a one-way humidifier. It gives off water until it runs dry or the air is saturated, and it cannot take moisture back. Left alone in a well-sealed box, it can push the humidity too high, which is how humidors end up with mold.
A two-way humidifier is designed to settle at a set humidity. It releases moisture when the air is drier than that level and absorbs moisture when the air is wetter. Most modern humidity control works this way, and the three common types below all aim for it.
Two-way humidity packs
A two-way humidity pack is a sealed pouch that holds a salt solution behind a membrane that lets water vapor pass but not liquid. A salt solution at the right strength holds the air around it at a fixed humidity, which is the principle behind the pack. Boveda, the best-known brand, lists its ingredients as food-grade salt, purified water, and a food-grade thickening agent, and says its packs hold the humidity within about two points either way when you use the recommended number.
Packs come in fixed humidity levels, and you choose one to suit the way you like your cigars. For example, Boveda sells 69% and 72% packs for cigar storage, an 84% pack made only for seasoning a new wooden humidor, and a 75% pack for checking a hygrometer.
Using them is simple: put the right number of packs in the humidor for its size and replace them when they go hard and crunchy, which means the water is used up. A few points to keep in mind:
- Don't mix different humidity levels in one box, and don't combine packs with another type of humidifier. The maker warns that they work against each other.
- Packs are disposable. They can't be refilled.
- Packs maintain humidity. They are not a fast way to season a dry cedar box.
Humidity beads and gel
Humidity beads are small beads of silica gel, usually sold in a tube or a tray, and treated so they settle at a set humidity such as 65% or 70%. Silica gel holds moisture on the surface of its pores, so beads can take in a lot of water and give it back slowly.
You recharge beads with distilled water only. Soak or wet them as the maker directs, drain the extra, and put them back. Never use propylene glycol solution on beads; it can ruin them. Holt's Cigar Company notes that beads are better at absorbing moisture than at releasing it, so they tend to suit humid climates, and they can struggle in a dry, air-conditioned room.
Foam humidifiers and PG solution
The traditional humidifier is a box or disk of absorbent foam, often green florist's foam, behind a grille. It can be filled with distilled water, but it is often charged with PG solution, a mix of propylene glycol and distilled water that is usually 50/50. Propylene glycol slows evaporation and pulls the humidity toward about 70%, which turns a one-way sponge into something close to a two-way humidifier.
The common problem is buildup. Propylene glycol barely evaporates, so if you refill again and again with the solution, the mix inside the foam grows stronger until it starts drying the air instead of humidifying it. Many makers say to charge with solution and then top up with distilled water. Follow the instructions for your unit, because formulas differ.
Use distilled water, not tap water, in any humidifier. Tap water leaves minerals behind and can encourage mold.
Electronic humidifiers
Large humidors, cabinets, and walk-in rooms often use an active (electronic) humidifier: a unit with a water reservoir, a fan, and a humidity sensor that turns the fan on when the reading drops. These hold large spaces well, but they are one-way. They can add moisture but cannot remove it, so they can't help if the room around them is already damp. Use only the water the maker specifies, and keep PG solution out of them.
Hygrometers: analog and digital
A hygrometer measures relative humidity. Two kinds are common in humidors:
- Analog dial hygrometers use a coil or other material that changes with moisture to move a needle. They look traditional, but many can't be trusted until you check them, and they drift.
- Digital hygrometers use an electronic sensor and show a number, often with the temperature. They are usually easier to read and steadier, but "pre-calibrated" on the box is not a promise. Ambient Weather, a maker of weather instruments, says most electronic humidity sensors are accurate to about plus or minus 3 to 5 points.
Either kind is only as good as its last check. Put the hygrometer where the cigars are, not right next to the humidifier, and give it time to settle after you close the lid.
Calibrating with a salt test
A salt test checks a hygrometer against a known humidity. A saturated mix of ordinary table salt (sodium chloride) and water holds the air above it at about 75% RH, and that figure changes very little at normal room temperatures.
1. Put a little table salt in a small open container, such as a bottle cap, and add just enough water to make a damp slurry. You want wet salt, not salt water. 2. Seal the container and the hygrometer together in a zip-top bag or an airtight box, without letting the salt touch the hygrometer. 3. Leave it at room temperature for at least several hours. Overnight or 24 hours is safer. 4. Read the hygrometer without opening the bag. If it reads 75%, it is accurate. If it reads 71%, it reads 4 points low, so add 4 to future readings or adjust the hygrometer if it has a setting for that.
Ready-made calibration kits do the same job with a 75% pack in a sealed bag. Boveda recommends calibrating a new hygrometer before first use and checking it every six months.
Tupperdors and coolerdors
A humidor doesn't have to be wood. A tupperdor is an airtight plastic food container used as a humidor, and a "coolerdor" is the same idea with a picnic cooler for larger collections. Both seal well, cost little, and need no seasoning because plastic doesn't absorb water the way cedar does. Pair them with two-way packs or beads, not a plain sponge, since a tight plastic box with an uncontrolled water source can turn into a damp terrarium. Some owners add a sheet of Spanish cedar for its aroma and as a small moisture buffer. Travel humidors work the same way for the road.
Rescuing dry cigars
If cigars have dried out, bring them back slowly. A dry wrapper that takes on a lot of moisture all at once can swell and split. Don't wet the cigars, steam them, or drop them straight into a damp humidor.
The usual approach is to raise the humidity in stages. Start the cigars in a sealed bag or box at a lower humidity than your target, for example with a pack at the low end of the range, and leave them for several days. Then move them into your normal humidor. Badly dried cigars can take weeks to recover. Some flavor may never return, and a cigar with a cracked wrapper is better smoked soon than stored.
Signs something is wrong
- Reading stuck high, or a musty smell: too much water or too little air exchange. Remove some humidification, air the box, and check for mold.
- Reading falls fast after every refill: the seal may leak, the wood may need re-seasoning, or the room is very dry.
- Cigars feel spongy or burn poorly: the box is likely too humid, even if the hygrometer says otherwise. Calibrate it.
- Cigars feel crisp or crack when you cut them: too dry. Rescue them slowly, as above.
Where to go next
- Humidor storage and the humidor buying guide
- How to season a humidor
- Spanish cedar
- Travel humidors
- Terms: relative humidity, hygrometer, two way humidity pack, humidity beads, pg solution, salt test, tupperdor, and the rest of the glossary
Smoke Rings sells the tools and not the tobacco: humidors, cutters, and lighters, sold through eBay (seller us-grai), plus empty cigar boxes for collectors. For the cigars themselves, our sponsor AbsoluteCigars.com is your best source.
Sources: Boveda (store and help pages, checked Oct. 30, 2026: pack ingredients, plus or minus 2% RH claim, B69/B72 cigar storage, B84 seasoning, B75 calibration kit, do not mix RH levels or combine with other humidifiers, calibrate new hygrometers and every six months). Conservation Physics, 'Properties of selected saturated salt solutions' (sodium chloride about 75% RH at 5 to 25 °C). U.S. National Bureau of Standards Letter Circular 1026 (saturated salt solutions as fixed humidity points). Ambient Weather support (saturated salt test; electronic sensors typically plus or minus 3 to 5%). Tobacconist University, 'Propylene Glycol (PG) Humidifiers' (PG slows evaporation; glycol buildup; follow maker instructions). Holt's Cigar Company humidification buying guide (silica beads, distilled water only, better in humid climates). Famous Smoke Shop Cigar Advisor (PG concentration buildup; active humidifiers are one-way).