A humidor is a tightly sealed box where a microclimate is created to ensure a stable relative humidity (RH). The ideal relative humidity for cigars is anywhere between 65% and 72%. Cigars are made and rolled in tropical climates and they need a humidity and temperature that simulates that of their place of origin. If you leave a cigar outside in your 30% humidity weather, it will dry, break, unravel and taste harsh and bitter. If the humidity is too high your cigar will absorb all that moisture and develop mold and its taste would be ruined as well. This is the reason why you need a humidor.
A humidor kit may contain a variety of humidor accessories: humidifier, hygrometer, and thermometer. Each part plays an important role, but the only indispensable device is the humidifier.
There are several types of humidifiers; among the most widely used is the Credo type humidifier. This device is essentially a plastic container with holes. Inside, the container is filled with foam or sponge. The foam is usually oasis green foam like the one used by florists for flower arrangements and it is soaked in a propylene glycol and distilled water activation solution. The purpose of the solution is to both kill bacteria and help maintain a 70% RH. The Credo type humidifier needs to be recharged with distilled water frequently. The frequency depends on your climate and will vary from every week to every 2 months. It also needs to be recharged with activation solution every 6 months to a year.
Here's a tip: every time you charge your humidifier with activation solution you should rinse with distilled water and let air dry first, and then soak with the activation solution. Make sure no solution drips before placing your cigars in the humidor.
A variation of the Credo type humidifier is the Western Humifier ® and Torpedo ®. These humidifiers undergo a special process at the factory so that they only require to be recharged with distilled water. Propylene glycol is not necessary.
Another type of humidifier is the electronic humidifier. They are more reliable and require less maintenance than the passive foam or sponge humidifiers. Usually all you need to do with electronic humidifiers is replace or refill the water cartridge every year. As an added bonus, many electronic humidifiers, like the Cigar Oasis ®, contain a filter to eliminate odors inside the humidor. For these reasons, they are the accessory of choice for large humidors and display cases. Electronic humidifiers, however, are more expensive than sponge or foam humidifiers.
Tip: Here is a nice info-graphic to help you choose the Humidifier what will work best for your needs:
Another humidor accessory is the hygrometer. You can feel your cigars to find whether they are too dry or too moist, but remember that the less you handle your cigars the better. If you want to know the exact RH inside your humidor you will need a hygrometer to check for changes in the humidity level. As a rule of thumb, if humidity drops under 65%, it is time to add distilled water to the humidifier.
You will find in the market analog and digital hygrometers. Analog hygrometers are commonly made with a metal spring, but some are made with natural or synthetic hair. Digital hygrometers take a few seconds to show changes in humidity level, but they are easier to read and do not require calibration. This does not mean that they are 100% accurate, so you still need to check the calibration of your hygrometer whether it is analog or digital.
To check your hygrometer’s calibration, there is a simple test using salt. Place your hygrometer inside a ziplock bag. Also inside the bag, you will place a small container with table salt that you have moistened with a few drops of water. Seal the bag and wait at least 6-8 hours. Check the hygrometer without opening the bag. The hygrometer should read 75%, the relative humidity of the salt/water mixture. With analog hygrometers you can adjust the needle to the correct humidity by turning the screw on the back of the hygrometer. If you own a digital hygrometer all you need to do is add or subtract the difference when reading.
It is also a nice idea to have a thermometer inside your humidor. Temperatures over 72º F (22º C) can make the cigars susceptible to a tobacco beetle infestation. Some digital hygrometers like the Western Caliber III ® have an integrated thermometer, which can be very convenient.