Monday, December 27, 2010

Using Hygrometers to Measure Humidity

When it comes to aging your cheese, one of the most useful devices to have is a hygrometer (to measure humidity) or a thermo-hygrometer (to measure both humidity and temperature).

These devices are sold at hardware stores, discount stores, hobby stores, Amazon and other online retailers, as well as eBay.  They range from $1 on eBay to hundreds of dollars at the labware websites.  However, for cheesemaking purposes, you can easily find a good one for less than $50.

Mechanical Hygrometer

The simplest ones are the mechanical ones, like the one Jim Wallace (our technical advisor) uses in his cave:
Jim's model now sells for over $100.  But, there are less expensive ones:
Sauna Hygrometer Thermometer Combo, Up North Sundries, 5' diameter, $55.99
Home Depot, 8.5" Thermometer with Humidity, $2.98
There are many inexpensive analog hygrometers offered online.  However, be careful when buying the very small ones which might have been made for a humidor, like the one in the picture below (unless you get several of them from eBay for a few dollars each).  They are not necessarily as accurate as you might like.  The advantage is their size (often less than 2" diameter) so they will fit in even your smallest containers.  Many cheese makers buy 3 or more of these at a time on eBay.
Cuban Crafter, PTHYG-MIO, $6.99, 1.75" diameter


With mechanical hygrometers, even if you pay more for a good one, you might have to calibrate it more often than you would like.  (For directions to calibrate, click here.)  If your hygrometer doesn't have a calibration adjustment, follow the directions to the point where you know the difference between readings on your hygrometer and the actual humidity.  Then, always add or subtract the difference from your readings.

Electronic Hygrometers

Digital hygrometers and thermo-hygrometers are sold at most hardware stores and the large discount stores.  They usually require a battery and they do not have a calibration adjustment.  However, you can test their accuracy by following the same directions for calibration above.  They also take a little longer to adjust to changes in the humidity.  When checking calibration, it is recommended that you wait at least 2 hours.

There are literally thousands of models online.  They come in all different sizes and prices, but there are certain features you would want to consider when buying one:

1.  The size of the hygrometer is important.  If you are using small containers, you need the smaller hygrometers.  
Digital-Edmunds Scientifics, $69.95,  Fits in shirt pocket.

2.  The size of the numbers on the display screen is important.  If you are looking at your device from the outside of a clear plastic container or a wine refrigerator, you want to be able to read the numbers.
3.  The sensor situation:  Sensors enable you to read the results outside of your "cave."  You may not need this feature in, for example, the above scenario where you are using a clear container or a wine refrigerator with a glass front.

Sensors can be very useful, however, when your cave is an old refrigerator or a closet because every time you open the unit to check the humidity, you expose your cheese to ambiant bacteria.   There are two kinds of sensors- wired and wireless.  Needless to say, the units with wireless sensors are much more convenient and they can be used further away from your cave.  Of course, they are also more expensive.

Here's a popular thermo-hygrometer with a 10' wire sensor.  Unfortunately, the sensor is for temperature only which seems to often be the case.
Indoor-outdoor with 10' probe, $9-$14 at Amazon, Ace, Grainger, Sears, etc.
4.  Most of the digital ones have a min/max function where you set the highest and lowest temperatures and humidity and when they reach the min or max, a buzzer goes off.  But, let's say you go away for a few days and when you come back, you want to know how hot or how humid it got.  If you had set the min/max before you left, the device would tell you the highest and lowest points it reached while you were gone.

One of the best digital thermo-hygrometers is probably the one below.  It is wireless and you can buy it with or without the sensor.  (I have seen it on e-Bay where you can Buy It Now for $20, including the sensor.)  Although the sensor is said to have a range of 100 ft., according to Cheese Forum, if the unit is located inside a steel refrigerator, the reach will actually be 10-15 ft.
Amazon, Honeywell TM005X Wireless Indoor/Outdoor Thermo-Hygrometer, $23.19

Amazon,  Honeywell TS33C Temperature and Humidity Sensor with LCD,  $23.47
In conclusion, if you have room in your cave for an analog (mechanical) hygrometer with a calibration adjustment, that will be sufficient.  If you need a sensor, the wireless ones will be the most convenient.  In any case, hygrometers are well worth the cost.

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