Humidifiers/hygrometers arghhhhh!

[mburkes]

I have got the hang of putting more moisture into the air for my buddies. But..I am having trouble monitoring. The mando room has four, yes four hygrometers. One in the Travelite case, one radio shack electronic, one in my intelli tuner/metronome and one on the humidifier. There is a 20% [26%-48%] measured variance on the four.
So, what have y'all found to be an effective way to monitor or the "perfect" device??
Thanks!
Mike http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif

[RevJB]

I would think the one in the case is what you should go by, since the instrument is kept in that tight space the longest... but that's just my opinion.

[Jason Holmes]

I've been using a Caliber III hygrometer/thermometer in my case(s), as well as a Humistat small instrument humidifier. The Caliber III works nicely, is very small, and claims to be the most accurate digital hygrometer out there. One can be had for around $20.

[LKN2MYIS]

I believe that the digital hygrometers are not as accurate / reliable as a 'hair hygrometer'.

I have a digital automatic room humidifier. I have it set to an unbelievably high 65%. However, over my instruments (which are in their cases), I have a hair hygrometer. This gives me a reading of about 52%. A random, sit-on-the-desk-cigar-type humidifier shows me that it's 60% humid.

(I like it a little wetter in the air, and I believe that not all that moisture gets into the cases.)

The hygrometers that are in the cases show about 48% humidity.

So - what does this tell me? I don't trust the digitals or the case ones. Two digitals in my room, side by side, often show a variance of up to 10%. I've had someone bring over a third digital, and that reading is off too.

I trust the hair hygrometer TO A DEGREE.

I have used the set-up I currently have for years, and have never experienced any instrument problems. I have oil heat and live in the Northeast. When the heat comes on, the moisture is just sucked out of the air at an incredible rate.

You need to find out what works in YOUR environment, to make a long story longer than it should be.

[alanz]

I'm using a Caliber III hygrometer along with a Damp-It in my case. So far, so good, about 40% humidity in the case.

[mzuch]

You might try calibrating your hygrometers using the salt test (http://www.cigarsinternational.com/html/cig101_12st.asp), long used by cigar smokers.

[jim_n_virginia]

I use a Radio Shack Hygrometer ($20) and it seems to work pretty good. Have never had a problem with it or my instruments in the 2 years I have had it.

I also use Damp-it's in the case. Works for me! http://www.mandolincafe.net/iB_html/non-cgi/emoticons/mandosmiley.gif

[LKN2MYIS]

You might try calibrating your hygrometers using the salt test (http://www.cigarsinternational.com/html/cig101_12st.asp), long used by cigar smokers.

You should ALWAYS calibrate hygrometers.
However, I've found that the digital ones are so inacurate that it's scary.

A cigar has different needs and tolerances than an instrument.

I'm also not a real big fan of putting anything with water in a case with a wooden instrument. I'm much more comfortable humidifying the room where the instrument is. This way, when I take it out of the case, I know that the humidity is still fine. When I'm out of the house with it, there is, of course, little you dcan do about the humidity - you just need to be aware.

I knew a guy that routinely, without giving it a second thought, ALWAYS put his instruments (in their cases) over forced hot air vents in his house. He lost a good guitar that way.

[Dave Cohen]

I used to use digital hygrometers in my shop. One was a little panel-mount one from Edmund Scientific, and the other was the one from Radio Shack. They were good for a while, but gradually read lower and lower values, while staying within 5% of each other. Dust and other culprits eventually foul the sensors. At some point, I got a couple of thermometers and mounted them on a board. The bulb on one was left open to the shop atmosphere. I fixed a gauze wick around the other, and had the end of the wick dip into a small container of distilled water. That thermometer is the "wet bulb" thermometer. A small muffin fan was mounted near the wet bulb thermometer, oriented so that it would pull air past the bulb. I switch it on and let it go for a few minutes, read the temperature on each thermometer for the difference, then read from the difference to the relative humidity and dew point on a table (photocopied from The Handbook of Chemistry and Physics). Simple and very reliable.

When my homemade hygrometer indicates 45% or so, the digitals are now saying 25-30%, which is completely innacurate in Central Virginia. Only occasionally do we get air masses that dry. So, the point is that the digitals are OK if you plan on replacing them every two years or so. Or maybe every year, just to be safe. Or, you can make a homemade wet bulb/dry bulb hygrometer for less than or about the price of one digital, and be done with it. If you do, be sure to use fresh distilled water each day, and change the wick before it starts to look grody.

http://www.Cohenmando.com

[GVD]

I've used a wide variety of hygrometers in my line of work over the years and for accuracy I still haven't seen anything beat a good old sling psychrometer. Here's how to make your own pretty cheap.

Build your own Psychrometer (http://www.flinnsci.com/Documents/demoPDFs/EarthSci/ES10301.pdf)

GVD

[earthsave]

Caliber makes the most accurate of the inexpensive hygrometers I have bought.

I've bought radio shack, a couple different little havanas, and a walmart that I recall. All of these digitals, when salt tested, were up to 8% on the high end.

The Caliber II was pretty much dead on. It is one of the few that is actually still working too. Keep it where you store your instrument, preferably in the case.

We have a small house and tower humidifier that does a pretty good job keeping us above 30%.

[Got8Strings]

That's a cool design! Dave indicated the need to use distilled water. Why is that important?

[LKN2MYIS]

My feeling is that if your instruments are valuable to you (not only resale value, but of inherent value to you), you don't want to take the cheapest way out in protecting them.

So some investigation and find the right tools to ensure their safety. Pay the money for the right solution and you won't be worried.

Just my opinion.

I know a guy with a VERY expensive instrument collection (towards 6 figures), and he's always screwing around with $20 hygrometers, home made humidifiers, etc., and he's always annoyed. He should just spend the money once, get a quality product, and stop fretting (no pun intended) about it.

[Dave Cohen]

If you don't use distilled water, you will get incorrect results. What a hygrometer responds to is the tendency for water to evaporate off of the surface of the thermometer bulb. Put salt, or sugar, or anything else that dissolves in water into the water, and the water evaporates at a different rate. At the molecular level, water molecules are attracted to each other, and the rate of evaporation depends on that. Put molecules (e.g., sugar, alcohol,..,) or ions (e.g., Na+, Cl- from table salt) that dissolve in water into solution, and you then have additional attractive forces between the water molecules and the other molecules or ions. Those additional attractive forces result in "sticky" collisions between the water molecules and the other molecules or ions, with the result that the water molecules in those collisions are prevented from immediately evaporating out of solution. Hence, the rate of evaporation slows. See "colligative properties" in any introductory chemistry textbook.

[Got8Strings]

Same holds true for tap water? Due to dissolved minerals?

[Dave Cohen]

Tap water has salts in it, also chlorine, maybe chloramine, and lots of other things, e.g., bacteria, in small amounts. The amount of salts and other impurities in tap water is small compared to sea water, but large compared to distilled or deionized water. If you buy a gallon of distilled water at your nearest grocer, it will last you long enough that it will grow bacteria and you will have to throw part of it away long before you could possibly use it up. Same goes for a small roll of gauze.

[earthsave]

That's a cool design! #Dave indicated the need to use distilled water. #Why is that important?
For cigar type humidifiers, definitely use distilled water. It less than $1 a gallon. Tap water and even filtered water will quickly promote mold growth.

If not, you'll get a moldy humidifier. For cigars, this is extra bad, because they are stored at ideally 65-70% humidity and less than 70 degrees, which is almost heaven for mold to grow.

[Mr. Loar]

I seem to have the perfect environment for all my instruments. Is stays a consistent 65% humidity in my house in the winter. I blame this on a 85,000 btu gas fireplace that I run as a partial heat source. My old house was an environmental nightmare for instruments because I stored them in a basement that was damp in the summer. It was dry in the winter because of a coal stove.

[AlanN]

I've always read bt. 40-50% relative humidity is ideal.

[Mr. Loar]

I aim for 65% because it is a mean average based on my climate area. It's hard for me to control summer humidity, but I can control the winter.

[Larry Simonson]

I was wondering about the above stated need for using distilled water in a hygrometer. It is true that the addition of salts or minerals to water do affect its willingness to evaporate as Dr. Cohen has stated, thus decreasing the accuracy of the wet-dry bulb method of humidity measurement, but for common drinking water the total amount of dissolved solids is so small that the effect on the measurement is negligible.

If 500 mg (more than in most drinking water) of solids dissolve in 1 liter of water and these solutes have an average molar mass of 50 g/mole, then the mole fraction of the solutes is .01/55 or about 0.0002 . The vapor pressure of this solution would be 0.02% lower than that of pure water and the measurement of humidity would be off by that same amount. Not enough to measure.

[Dave Cohen]

Larry, true enough. You can certainly get a single good rh reading with tap water. If you get casual, though, and let the water evaporate in the little cup before changing it, you are effectively preconcentrating salts in the cup, and especially on the wick. When I did that, I started seeing erroneously high rh values. I found it to be a lot easier to just use distilled water. I also found that a gauze or cheesecloth wick which stays wet can hold a lot of impurities, and also grow zoo breath. It is both convenient and inexpensive to (a) use distilled water, and (b) change the wick frequently. Also gives peace of mind.

[Larry Simonson]

In my above post I did not intend to give the impression that using ordinary tap water is wise and Dr. Cohen has listed very good practical reasons for not using it.

[Mr. Loar]

People used to tell me to put 1/2 an apple in the case. Anyone ever do that?

[JeffD]

1/2 an apple
I used to do that for years and years. I never measured anything, but never had any humidity related problems, and with the apple the mandolin did not drift out of tune as often or as far.

Also, the case smelled great when I opened it.


But now I have a room humidifier, and I keep the humidity above 40%. I don't use anything in the case.

[Glassweb]

Since moving to Florida last year I've definitely seen how high humidity can affect the sound/playability of a string instrument. Once it gets above 60% the tone and volume suffer... and keeping my mandolins in tune is a real pain (what else is new?!).