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How to Calibrate a Hygrometer with the Hygrometer Salt Test

Keeping your hygrometer in working order is crucial for the humidity of your humidor, and for the quality of your cigars within it. Whether you use an analog or digital hygrometer, you need to make sure it is giving off a proper reading, otherwise you risk your cigars drying out. Calibrating your hygrometer is the best way to guarantee that it is working properly and giving a correct reading, and while a one-step calibration kit is the easiest way, there’s another method that uses household items that will allow you to test your hygrometer’s settings: the Hygrometer Salt Test. The salt test works to calibrate both analog and digital hygrometers the same way. The process works similarly to using a one-step calibration kit, only we will be making our own homemade humidity pack in place of the premade humidity pack found in one-step kits.

You Will Need:

  • Recloseable Plastic Bag (larger than your hydrometer)
  • Small bottle cap
  • Table Salt
  • Water

Take the bottle cap and add one tablespoon of salt. Then, add a VERY small amount of water. The amount of water you add to the salt is key. You want to get the consistency of a salt paste. You don’t want saltwater in your bottle cap—that is WAY too much water! You want just enough water to turn the salt into a lumpy paste. Add the bottle cap full of salt paste to your recloseable plastic bag. The salt paste will create approximately 75% relative humidity within your recloseable pouch once it has been sealed.

Now to calibrate the hygrometer. Insert the hygrometer in with the salt paste cap. Make sure the sensors on the hygrometer are clear and able to take in the humidity. On an analog hygrometer, the sensors can be on the back (underneath the magnet) or on the sides (underneath the grommet). Digital hygrometers usually have sensors on the front, so make sure those are facing up. If your recloseable pouch is large enough, you can test more than one hygrometer at a time.

Seal the pouch and leave it be. You will need to keep the hygrometer inside the pouch for 8-12 hours. Do not disturb the pouch while your hygrometers are in there, or else you may throw off your reading.

Your hygrometer should read within a 2% margin of error from 75% (so, anywhere from 73%-77% will suffice). If the reading is correct, your hygrometer has passed the salt test and is properly calibrated. If the reading isn’t correct, you’ll need to adjust the hygrometer accordingly. Analog hygrometers have an adjustment screw, often found on the back. Digital hygrometers often have an adjustment knob on the front. Once you are done adjusting the hygrometer, place it back in the pouch and seal it again for a few hours to see if it yields a proper reading.

If you would rather not adjust your hygrometer, you can simply remember the deviation that the hygrometer is from the proper reading. If it is reading 70% when it should be reading 75%, your hygrometer reads 5% low, and you can just do the mental math in your head every time you wish to look at your humidity reading. While adjusting your hygrometer may seem like a pain, it’s worth the time to adjust it so it reads accurately.

We know that a lot of digital hygrometers often state that they are pre-calibrated in the factory. Honestly, we still recommend that you calibrate your hygrometer before using it. Seriously, it’s better to be safe and take a few hours to properly calibrate your hygrometer, which will spare you from possibly ruining your cigars.

Once your hygrometer is properly calibrated, you can place it back in or on your humidor.