How to salt test your hygrometer

[Mark C]

My Boveda packet is out of date, and I wasn’t able to find what I considered a GOOD guide to salt testing a hygrometer anywhere online. Everything I read said ‘cap full of water’ or ‘just a few drops’, ‘just enough to wet it’, etc. I kept convincing myself I was screwing up the test because I didn’t have precise instructions, so I figured a few experiments were in order.

Materials:
Airtight container (some suggest Ziploc bags, I used a disposable Tupperware container)
Container for salt (most sites suggest bottle caps, I used a graduated
shotglass to make measurements easier)
2 parts salt

(I used regular table salt, Part II of this ‘how to’ will verify that sea salt and kosher salt work as well)
1 part Distilled Water

Stirrer (toothpick, coffee stirrer, etc)

Procedure:
1) Fill a shotglass with ½ tablespoon of salt.

2) Add ¾ teaspoons of distilled water.
3) Mix the salt and water together, toothpicks work great. You should end up with a sort of salt slurry.

4) Place the hygrometer and shotglass into the airtight container, seal it shut, and wait.

5) After ~8 hrs, your container should have reached 75% RH. Make a note of the reading on your hygrometer and how far off it is from 75%.

6) If your hygrometer is adjusted, make a small adjustment and repeat the test until it does read 75%. If it is not adjustable, I write the difference on the back of the hygrometer.

While this test is somewhat dependent on temperature, the difference in RH is so small it will not be seen with a standard cigar hygrometer. In other words, temperature is not a factor for our purposes.

I have two hygrometers, so I did the test in separate containers, with different amounts of salt. One container had 1 tablespoon of salt, with 1.5 teaspoons of water, while the other container had ½ tablespoon of salt, and ¾ teaspoons of water. Both proved to yield equal results. I let them sit overnight so I’m not sure if one equilibrated faster than the other. I suspect they both were similar. I’m sure there’s a minimum quantity of salt/water, but it looks like I was well above that point during this test.

Follow-on Experiments:
1) Vary the water to salt ratio, trying to find the upper and lower bounds for an effective salt test.
2) Verify that kosher and sea salt work as well as iodized table salt.
3) Find the minimum amount of salt/water necessary for a given container.

If you've got any questions or comments please let me know, especially if I screwed something up along the way!

[Bruzee]

Great tutorial! I wish this was around when I was getting started. Thanks for the work!

[Mugen910]

thanks for the info..I always forget to do this...that's prob why I throw in 2-3 hygrometers in my Vino just to take the avg.

[Sailchaser]

Great post, simple and easy for anyone to follow , thanks for taking the time to post

[Ollie]

Good post. I think I was using way to little water in my test. I will re-test tonight.

[TomHagen]

Thanks for this great pictoral post!! Makes it simple and easy to follow!! I actually have a new adjustable hydrometer coming today, very timely!

[shilala]

Absolutely awesome post, Mark.
I'll be pointing it out to folks on a regular basis, I'm sure.
Thank You!!!

[hotreds]

Sticky time!

[Mark C]

UPDATE:

Here's the temperature vs. RH data for NaCl (table salt). I copied this from a post at the Stogie Guys blog. While I can't site a specific source, I found one or two other pages online that agree with these numbers. This should give you a better idea exactly how negligible the ambient temperature is for this test.

Degrees Celsius versus RH of saturated salt solution:
0*C
75.51 ± 0.34 % RH
5*C
75.65 ± 0.27 % RH
10*C
75.67 ± 0.22 % RH
15*C
75.61 ± 0.18 % RH
20*C
75.47 ± 0.14 % RH
25*C
75.29 ± 0.12 % RH
30*C
75.09 ± 0.11 % RH
35*C
74.87 ± 0.12 % RH
40*C
74.68 ± 0.13 % RH
45*C
74.52 ± 0.16 % RH
50*C
74.43 ± 0.19 % RH
55*C
74.41 ± 0.24 % RH
60*C
74.50 ± 0.30 % RH
65*C
74.71 ± 0.37 % RH
70*C
75.06 ± 0.45 % RH
75*C
75.58 ± 0.55 % RH
80*C
76.29 ± 0.65 % RH

I'd appreciate it if a mod could append this to my original post. Thanks!

[shilala]

Here's a sweet piece of info, too...
When we calibrate our hygrometers at 75%, that's the point where they're accurate (calibrated).
At 65% they can be 3 or 4 points off, and are usually at least 2 points off. (I say that from experience. I use somewhere around 20 hygrometers for making beads and I calibrate them all at least once a month.)

It really doesn't matter, either.
The hygrometer is just a guide. If my cigars are smoking well at what my hygrometer says is 65% but is actually 63%, it really means nothing.
If my hygrometer says 69% and it's really 60%, same thing.
The only time the inaccuracy comes into play is if I switch hygrometers. If I put a new one in and it reads 61% where the old one read 69%, I'm sure not going to start trying to get my RH%age up.

Another thing about hygrometers is that once the battery gets low, they are notoriously wonky. The very first thing I do when a hygro in one of my humis is off?
I get a different hygrometer and put it in there.
Then I change the battery in the screwy one.
99% of the time it's the hygro that's screwed up and not my humi.

All that was to say this...
Trust your cigars first and your hygrometer second.
After a period of time, you're honestly going to be able to pick up a cigar and know immediately if it's too dry or too wet.

[Mark C]

Good points Scott, thanks for adding that! Another part of my future testing will be inclusion of a lab-quality Fluke hygrometer, with NIST-traceable calibration. That ought to tell us a little something about the hygrometer accuracy. Like you said, not important, but the nerd in me is interested.

[RichardW]

Good post, Mark. It's been several years since I bought a hygrometer -- still have a few old Radio Shack models (only one is adjustable). What models (adjustable) are available on the market nowadays? and do the inmates have any recommendations?

TIA

[TomHagen]

does it matter if it is ''lite'' salt - 1/2 sodium???

[Mark C]

Originally Posted by TomHagen

does it matter if it is ''lite'' salt - 1/2 sodium???

Now that's a good question. I'll have to see if I can find that at the store and try it out.

[TomHagen]

I salt tested my Western Caliber III and Hydroset for the last 18 hrs. following the OP's instructions But with 100% Sea Salt, (decided not to use the Mortons lite-salt) after having tested with a 3+ month old Boveda Cali pack...

BOOM!!

Both results were exactly the same...
and it only took about -10 hrs for results!! The results have now been consistant for 8 hrs...

The Western was +2 as it was 3 months ago, while the Hygroset was way off, and is now calibrated and on the $!! The temp of both is consistantly 2 degrees apart.

Here is my main question...

Has anyone else seen that the Western Caliber III is WAY more responsive than the HygroSet????

The Hygro takes awhile to catch up to the ambient RH, which is has its advantages and disadvantages for taking reading in open humi's.

[kugie]

Thank you

[paris1129]

I need to do this myself! Thanks for the great step by step!

[Flat4boxer]

I need this, thanks

[kelmac07]

Great info guys...thanks.