HOW TO: Salt Test (hygrometer calibration)

[CHRIS7891011]

Salt Test. Use this to test your hygrometer to see how far off it is!

Step 1 - Get an airtight container. Some peopel say zip-lock bags but i dont buy that.

Step 2 - Place some salt in a lid of a soda bottle or other small container

Step 3 - moisten the salt with water... don't flood it just dampen it

Step 4 - Place the salt as well as the hygrometer in question in the container and close the lid tightly. Let it sit for at least 8-12 hours

Step 5 - After that time the humidity in the container will be 75%. Don't ask me how its just how nature works. Check the number your hygrometer is reading. If its other then 75 then you now know how far off it is. change it to the correct reading or remember how far off it is for the next time you want to read it.

Step 6 - enjoy your cigar a little bit more now that you know your hygrometer is accurate.

Here's a visual for you!

[GatorMike]

Nice guide Chris. And if you're extra lazy you can always buy a boveda!

[Vinpuros]

Thanks Chris,

You have pointed me in the right direction. Is it possible adjust the digital hygrometers? If so, how?

By the way, I used to live in Chicago. I consider it to be "the birth place of my second childhood". I lived thier for about ten years. Love the windy city.

[full count]

Originally Posted by GatorMike

Nice guide Chris. And if you're extra lazy you can always buy a boveda!

These are right on! They will keep for a few months if sealed back up properly.

[CHRIS7891011]

Originally Posted by Vinpuros

Thanks Chris,

You have pointed me in the right direction. Is it possible adjust the digital hygrometers? If so, how?

By the way, I used to live in Chicago. I consider it to be "the birth place of my second childhood". I lived thier for about ten years. Love the windy city.

It differers depending on the model you use. I bought a cheap one from Target for about 10 bucks but i can't adjust it. However it exactly correct.

I think there is a link another thread to a kit that you can buy that can be adjusted.

[PremiumsOnly]

For those using a different salt (lithium chloride in da house!) or even boring old table salt, you can see a list of RH at a range of temperatures on Omega's website.

http://www.omega.com/temperature/Z/pdf/z103.pdf

::WARNING:: Scientific Content Ahead

As for the explanation as to why it is provides a constant humidity all has to do with chemical equilibrium. If no salt were present, the humidity would reach some equilibrium value (100% RH in a sealed bag). With the salt, the equilibrium value is lowered as it dilutes the water (odd phrase to think of I know), and prevents some molecules from escaping. The system reaches an equilibrium lower than that of a pure water solution, and for sodium chloride, ~75%.

Only dampening the salt rather than flooding it is so that the salt concentration remains constant in the solution (at a saturated level), and will not change whether water enters or leaves the solution. So if you put too much water, the expected RH of 75% will be in actuality higher by some unknown value.

Oh, and another thing, the technique breaks down if the ambient RH when you start is higher than the equilibrium humidity of the saturated salt solution (75%). So don't try using it outdoors in the south! The reasoning (as if you cared) is because the salt at the surface absorbs the excess moisture, not distributing it to the rest of the salt mass, leaving you with a not saturated salt solution on the surface and a wacky RH to show for it.

END
::WARNING:: Scientific Content Ahead

[CHRIS7891011]

Thanks John! I have no clue what you said.

(nah i got it. Just had to read it a few times. )

[karmaz00]

thanks for that info just found that 1 of my digital is off by 3%

[maduromojo-cl]

Thanks Chris and John! I had no idea about this test until I joined CigarLive. I've had problems getting the humidity up in my humidor so I figured I'd give it a try. My Little Havana digital was dead on...70%!!! :angry: 5% off makes perfect sense. So the RH in my humidor has been hovering around 63-64% all this time (using a Diamond Crown Humidifier)!

Thanks again for posting this Chris it was a cool little experiment.

A side note on some details: I used an Arizona Ice Tea bottle cap (I noticed it was coated on the inside), kosher salt my wife cooks with, a mason jar, and distilled water dribbled on the salt. The temp hovered around 70 which was right for the room. Also, it was 70%RH when I checked it at 8 hours and still 70% after 15 hours.

[mtec-cl]

A 'perfect' recipe which I always used successfully is 1 Tablespoon of salt with 1 Teaspoon of water in a half cup measure or small shotglass. Mix it and put it in a an airtight container (tupperware is ok) with the hygrometer.

After 24 hours, check the reading without opening the container. After 36 hours, check it again and you should have your final reading.

Some hygrometers, especially new ones which have been resting in a rather low ambient humidity for a prolonged period of time, seem to require the 36 hours to get accustomed to a higher humidity. When I calibrate my HygroSets, the extra time (36 hours) makes it increase 1% RH when compared to 24 hours. But for any time after the 36 hours, the reading remaints constant and there is no more change. When testing new hygrometers, I throw in another hygrometer which I have tested before as a benchmark to ensure accuracy. For exmaple, if the previous one (benchmark unit) reads 2% off, then the new one should read 2% higher than the benchmark unit.

[iloveclmore]

I have tried this several times with my digital (unfortunately it is not adjustable), and it is WAY off. The three times I tried it, it has hovered around 63% or so. I didn't think it was that far off spec. Maybe I'm not doing it right. I've tried with zipperlock bags and a couple different tupperware containers with the same result. Maybe it is in the salt/water ratio. Do you have to use distilled or can you use plain tap water?

[CHRIS7891011]

I believe I used distilled water. What type of hygrometer do you have?

[iloveclmore]

I have one analog, and one digital. The digital has no brand on it, but I think it was from Madelaine. The analog came with my humidor.

[CHRIS7891011]

hmm ok, my only recommendation is to pick up a new one (unless you like simple math with cigars ) I got mine at Target and its spot on.

How long were you keeping the hygrometer in the container?

[FoZzMaN-cl]

I picked one up at WalMart for ~$6...