Calibrating a hygrometer?

[MattSkibaIsGOD]

Hey everybody, I noticed in the last few days that my 12 strings fret ends have become kinda sharp as well as my D550's. I saw on Brian Kimsey's site that that is a sign of reduced humidity. So, I went out today and bought a hygrometer from Radio Shack and a handful of cellulose sponges.

 

Is Kimsey's method of putting the meter in a bag with a bottle cap full of salt & water for a few hours the way to go? or is there something else? Thanks,

 

-Dave

[Samilyn]

I haven't read Kimsey's method, per se, but the bottlecap of salt + water + baggie is what I learned to do way back when, so it's probably the same. Wait 6 hours, should measure 75%.

 

I'm not aware of any other method.

[Queequeg]

Kimsey is highly respected in these parts.

 

The recommended and most accurate calibration method is to place the hygrometer together with a salt solution into a small plastic box. One should take a cup or spoon filled with salt and moisten it with a few drops of water. The salt should not dissolve, but merely be damp. Afterwards, place the hygrometer and the salt in a well-sealed plastic box and wait. After about 8 hours the humidity within the box should have reached a humidity of 75%. Then adjust the needle of the hygrometer with a screwdriver at the rear to indicate 75% humidity.

[MattSkibaIsGOD]

Thanks!

[Freeman Keller]

I've never known if the inexpensive hygrometers were very linear, but I've used the saturated salt/water method and assume that if it is off 10 percent at 75 % it will be 5% at 37 (which is about where we are usually measuring). I've also heard that if you wrap it in a wet wash cloth is should read 100 (duh).

[Samilyn]

 

I've never known if the inexpensive hygrometers were very linear, but I've used the saturated salt/water method and assume that if it is off 10 percent at 75 % it will be 5% at 37 (which is about where we are usually measuring). I've also heard that if you wrap it in a wet wash cloth is should read 100 (duh).

 

 

LOL. I've never heard that one. I've been lucky my mid-priced hygros have all been accurate after calibration.

[rjoxyz]

Are the amounts/ratio of salt and water, and the time left in the bag/box critical? I have wanted to do this for some time, but was unsure on these factors. For instance, can the hygrometer be left in the environment overnight? For a day? Can the salt be dissolved in the water or not?

 

Seems there is no clear consensus on methodology.

[Samilyn]

Are the amounts/ratio of salt and water, and the time left in the bag/box critical? I have wanted to do this for some time, but was unsure on these factors. For instance, can the hygrometer be left in the environment overnight? For a day? Can the salt be dissolved in the water or not? Seems there is no clear consensus on methodology.

 

The fact that there is no "etched-in-stone" consensus makes me think the ratio isn't that critical, but you're not supposed to get the salt so wet that it dissolves. I use 1 heaping teaspoon of salt and 3-4 drops of water from a small eyedropper. (The spoon is the measuring kind, not the eating kind - difference in volume there.)

 

I think the time limit has more to do with minimum time than with max. You simply can't rush this thing. Last time I did one, I bagged it just before I went to bed. Next morning, about 9 hours later, I checked it and it was right on the mark at 75%.

 

But I'm no expert - that's just my opinion and experience.

[Freeman Keller]

Are the amounts/ratio of salt and water, and the time left in the bag/box critical? I have wanted to do this for some time, but was unsure on these factors. For instance, can the hygrometer be left in the environment overnight? For a day? Can the salt be dissolved in the water or not? Seems there is no clear consensus on methodology.

 

My understanding is that a super saturated salt-water mixture is at equilibrium at 75 percen. What I did was filled a bottle cap 1/2 full of salt, poured water in so it was completely wet but not dissolved, put the whole shebang in a baggie with my Planet Wave hygrometer (which, as far as I can tell has no adjustment) and the next morning it was reading about 79%. I therefore assume that it is reading about 2 or 3 percent high at my normal room humidity of 35% or so - ie, the real value is maybe 32.

 

Just like setup, the whole idea isn't to be anal about some numbers but to have a general idea of where things are and if they are approaching a danger point. Right now my hygrometer is out in the shop and last night when I brought two snow covered cars in it went up to 80 percent (not the best conditions for guitar building).

 

They say that web pages devoted to cigars have lots more information about hygrometers and calibration - you might do some googling

[Samilyn]

My understanding is that a super saturated salt-water mixture is at equilibrium at 75 percen. What I did was filled a bottle cap 1/2 full of salt, poured water in so it was completely wet but not dissolved, put the whole shebang in a baggie with my Planet Wave hygrometer (which, as far as I can tell has no adjustment) and the next morning it was reading about 79%. I therefore assume that it is reading about 2 or 3 percent high at my normal room humidity of 35% or so - ie, the real value is maybe 32. Just like setup, the whole idea isn't to be anal about some numbers but to have a general idea of where things are and if they are approaching a danger point. Right now my hygrometer is out in the shop and last night when I brought two snow covered cars in it went up to 80 percent (not the best conditions for guitar building). They say that web pages devoted to cigars have lots more information about hygrometers and calibration - you might do some googling

 

Funny you should mention that. In another thread, I just recommended a tobacco store as a source of good hygrometers. That's where I got one of mine - place sold neat gifts in addition to high-end stogies and the hygro was an attractive one.

 

It's a pretty good bet that somebody who invests in $100 stogies is gonna be mighty picky about how he stores 'em.

[0rbitz9]

I've done the salt test a few times. I've found that the humidity levels in

a sealed container with saturated salt will still fluctuate, unless you can

keep the outside temperature realatively stable to within a few degrees.

I've gotten the most stable results by keeping the sealed container inside

an insulated cooler for 24 hours.

[Samilyn]

I've done the salt test a few times. I've found that the humidity levels in a sealed container with saturated salt will still fluctuate, unless you can keep the outside temperature realatively stable to within a few degrees. I've gotten the most stable results by keeping the sealed container inside an insulated cooler for 24 hours.

 

Excellent idea!

[happy-man]

 

... I've also heard that if you wrap it in a wet wash cloth is should read 100 (duh).

 

 

where I live you can just put it on the front porch... well not exactly... it didn't rain all day today.

 

Scott O

[Samilyn]

 

where I live you can just put it on the front porch... well not exactly... it didn't rain all day today. Scott O

 

 

LOL. Or set 'em out there on one of those sweltering days when ya have to wring out the air before you can breathe it and the gits sound like they're stuffed full of socks.