Calibration is important, as analog hygrometers are often wrong, sometimes by 10 percent or more. Accurate readings help keep your cigars properly humidified. Traditional approaches include wrapping a hygrometer in a moist towel or placing the device in an enclosed space -- such as a Tupperware container -- with a salt solution you mixed up yourself. The Humidipak calibration method works on essentially the same idea as the latter approach, but the test is readily packaged. It's quicker, easier and avoids any variables that arise from a do-it-yourself project.
The system, and all of Humidipak's products, is based on a scientific principle included in what's known as Raoult's Law and Henry's Law, which have been known for more than 100 years. It states that a saturated salt solution in water will contain a constant level of relative humidity in an enclosed chamber.
To use the Humidipak system, strip open the top of the bag and break the zip-lock seal. The bag, once opened, will last for up to three months. (A section to note the date of the opening is provided on the bag.) Place the hygrometer inside, close the bag and leave it at room temperature for approximately 24 to 36 hours. The environment inside will be 75.5 percent humidity -- the natural level maintained by salt when dampened and put in an enclosed environment -- and your hygrometer should read this within plus or minus 0.3 percentage points. If it reads differently, make a note and factor it in to future humidor readings.
Some of the better analog hygrometers on the market can be adjusted with a turn of a screw on the back of the device. Digital hygrometers, unfortunately, are beyond repair since they are regulated by an internal microprocessor. Most hygrometers, digital and analog alike, are calibrated to a specific degree of variation, which is denoted somewhere on the device itself or on the box in which it comes. Take a look before calibrating for even greater accuracy.
When the Humidipak idea initially came out in 2003, it incorporated three different bags equipped to provide exact humidification conditions. The hygrometer would be put in all three in escalating humidity levels so that the owner could get a supremely accurate read on the calibration of a hygrometer in varying conditions. Simplified to one bag, the current system is more user-friendly and cheaper than the first system, which had a suggested retail price of $50. The new one retails for $5.
You can also use the temporary humidor bags made by Humidipak for this purpose, which guarantee 69 percent humidity with a plus or minus 0.5 degree of variation.
Humidipak products are available at retail tobacconists.