If the humidor is built properly, the Spanish Cedar acts as a moisture buffer, so if the lid of the humidor is frequently opened, the interior RH returns quickly to its previously desired level.
Since the Spanish Cedar acts like a sponge, it will both absorb and desorb moisture. If the Spanish cedar lining in your humidor is very dry, as it usually is, when you first purchase it, then it can actually pull out the moisture in your cigars potentially damaging them. So in order to prevent this one must ‘season’, ‘prime’ or ‘condition’ your Spanish cedar lining to ensure a reliable, and stable internal microclimate.
The Process of Seasoning Your Humidor
1. The Easy Humidor Seasoning Method - Boveda Packs
For reliability, ease and least amount of work, I would highly recommend purchasing the One Step Seasoning Kit from Boveda. This will solve your humidor seasoning procedure with ease.
2. The Traditional Humidor Seasoning Method
A common and traditional method of seasoning a humidor is to wipe down the interior sides of the humidor with distilled water with a lint-free cloth. I used to recommend this process for all humidors, however since there is a vast amount of cheap humidors on the market, I would now avoid this procedure. On cheap humidors you could run the risk of over-expanding the interior lining causing structural joint failure.
Instead, I would let your humidifier do the work for you.
First of all, make sure the humidor is completely empty, and free of lint, dust or dirt. Fill your humidifier with proper solution and let it sit inside the humidor by itself. Close the lid and allow the Spanish Cedar to naturally absorb the moisture over the next few days. To expedite the process, you can also place an additional cup of distilled water inside your humidor.
Every day for the next 7-10 days, continue to top-up your humidifier with the proper solution. Monitor the internal Relative Humidity, and once it seems stable at around 70% +/- you can begin to introduce cigars to your humidor.
After a week and a half, you can go ahead and introduce your cigars into the humidor.
Priming your humidor is usually required only once, but by doing so, will ensure stable, consistent aging and maturation of your cigars for your smoking enjoyment.