A humidor is not a sealed container but a buffered one: the cedar itself holds moisture and trades it with the air. A new box arrives with its wood far drier than the 65–70% equilibrium it is meant to maintain, so for its first weeks it competes with the cigars for water and wins.
How long does it take?
Days to a couple of weeks, depending on the method, the size of the box and how dry it started. It is finished when the hygrometer holds steady at the target with the lid closed — not when a calendar says so.
The methods
The gentlest is passive: a shallow dish of distilled water, or a humidity pack rated above the working figure, left inside the closed box while the wood equilibrates. Wiping the interior with a distilled-water-damp cloth is faster and more contested — over-wetting can raise the grain or warp a panel, and the wood only needs to reach equilibrium, not to be soaked.
What never to use
Tap water, which carries minerals that foul a humidification element and can leave deposits on the wood. Alcohol or propylene glycol solutions belong only in devices designed for them, and never applied directly to the lining.