Official Luthiers Forum!

Okay, I'm obsessing over the rh issue again,
and have been looking everywhere online, hardware stores,
blah-blah, for a hygrometer.
From $10-$350.
Any advise on what kind?
Of course I like the Abbeon analog one for $172,
but if the Stew-Mac one for $27 works, I'd just get that.
Reading the archives, I see some folks use 2 hygros, and split the diff.
Also, if I processed wood in one location, then took it inside to glue up,
how long should it aclimate where the rh proper?

1)...Consider a wet bulb psychrometer. It's the standard by which other hygrometers are calibrated. You can make a setup for less than $20 and you'll know that you're always accurate.

2)...If you keep your wood stored in RH controlled room and only move it for a few hours to be sawn, drilled or routed, etc. then wait the same few hours once it's back in the RH controlled room before gluing. I have no data on this...just my rule of thumb that has served me well. The key is to keep the wood conditioned at all times.

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

I bought the StewMac one after looking at considerably higher priced units. I was looking for one that would register in the smallest increment possible. The StewMac one was the only one that advertised a 1% increment in that price range. I'm not certain how accurate it is but it consistently corroborates what my umidifier tells me.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I use a german made hygro inported by a local high end guitar shop, the 12th Fret (Toronto)... they used a swing sych to calibrate each one, and they are pretty accurate. they read to one percent. In the back of the guitar shop, they have about ten on a wall, and they all read within a couple percent of each other.

A friend came over with his used Abbeon, and a sling, and we checjked them both. Keep in mind that a sling only gets you so close, as the charts give a range, not an exact reading. It turns out that his Abbeon was in range, albeit the low side. My 12th fret hygro read one percent on the high side of the sling range, but I can ove the dial indicator back if needed.

So .. I am happy with where it sits, I built on the low side of most builders RH anyway, as I only brace at 40-42, on my hygro reading.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Surprised you brace at that %, Tony. Im not sure how much of a difference there would be between Toronto and here (2 hours north) but I have not seen the humidity drop below 50% (w/abbeon) here in over a year of keeping a constant eye on it, usually around 60-70%. I am wondering if I should maybe brace around 50%.

I keep my shop around 45%. Dehumidifier in summer and humidifier in the winter. I monitor the humidty with the Stew Mac hygrometer, and monitor that with a sling hygrometer. The Stew Mac one that I have has stayed +or- 2 percent of the sling so far.

Chuck

_________________
_________________

The American Abbeon is made by the German company Lufft. Some of the price goes into the fancy brass casing, but Lufft makes sensibly cheaper variants with a simpler casing but same guts. I have mine for 2 years now, paid about 70$ (ridiculous taxes included) and never had to calibrate it. Every few months I compare it to a wetdry measurements and it is always only ± 2-3% off .

More recently I got a Caliber III digital too - the one sold by Stew Mac - and it shows from 10 to 5 points lower than the Lufft. Roughly, 30% if the Lufft shows 40, 37 if Lufft 45 and so on. They get closer together at about 60% or so. I don't glue anything critical if the Lufft is over 45% (less than 40 on the Caliber)

_________________
Build log

Thank you all.

I’ve had an Abbeon RH for about 20 years. When I recently calibrated it I found it was reading about 6% high. To calibrate I used a neighbor’s Cole-Parmer meter checked against a sling psychrometer. This sling psychrometer gives a precise reading. It’s interesting to note that the $20 GE temp/RH meter in the last photo, while it gives fairly accurate indoor/outdoor temps, the RH is wildly off and I can find no way to calibrate it.

Joe

I use a sling psychrometer and this (often overlooked) simple device:



It hasn't disagreed with the sling psychrometer yet. I guess we are concerned with the effects of atmospheric moisture on wood. Being made of wood it reacts in a similar manner to Guitar woods. Makes perfect sense to me.

Ummmm ... Ed, you are kidding right ?? 60-70 percent all the time?? .. maybe thats outside ... but in the dead of winter, if its below freezing outside, and 50-60 %rh, and that air is then heated to 70 degrees inside, your RH will be about 15%-20% .... I have to humidify from dec thru april/may to get to 40%. If your house was 60-70 % all winter your windows would have about an inch of ice on the inside of them ... I get some at 40 ....

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

I swear my RH never went below 55 last winter .
I had to dehumidify all winter. My shop is heated by infloor in the concrete though, maybe that has something to do with it.

I did a lot of searching yesterday, and found out you can get one similar to the stew-mac, and you can get a kit to calibrate it.
The kit is a plastic bag with a sack of something in it that makes rh 75% all the time,
and you put the hygro in it, and calibrate it.
Pretty slick.
I'm going with that and going to try a sling hygro like Michaels.
I remember the post about that a while ago,
and will search that out.
Thanks again.

I guess its possible Ed .. but it seems very very weird to me ... if the heat source in the floor isnt adding humidity, I cant fathom where it comes from ...

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

If it's an old, unsealed floor, without a moisture barrier, it could be a very effective wick, bringing up ground moisture and causing it to evaporate into the room. Friends of mine had this issue in their house.

Pat

_________________
formerly known around here as burbank
_________________

http://www.patfosterguitars.com

The building is only about 6 years old and is pretty much state of the art.
I was surprised at first about the RH hearing how low it gets for everyone else in the winter but I just began to assume the humidity is abnormally high in the area.
Then again perhaps my Abbeon slipped through QC.

or its simply totally out of whack ....

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

A single calibration point at 75% is almost useless (unless your interested in building at 75%), you'd need to calibrate two points, one on each side of the reading your interested in.

_________________
Jim Watts
http://jameswattsguitars.com

There's some good info here: viewtopic.php?f=10101&t=27087&p=364087&hilit=hygrometer#p364087

I would recommend buying a sling psychrometer or fan powered psychrometer first so that you know and then buying a digital one to calibrate. My Caliber III is dead nutz accurate for some reason but I guess I'm lucky.

If at all possible, test your thermometers on the sling psychrometer too. On the first one I bought, one of the thermometers didn't work right and it gave wildly inaccurate results. I imagine that would be very unusual though.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Sling psychrometers aren't all that accurate. They're variability is in how slow or fast you swing it, how wet the wick is and so forth. You need to do several readings and then average them. I have the analog Lufft which I got from LMI but its only so accurate. I splurged a number of years ago and got the Lufft C200 several years ago. I calibrate everything from it. Its as accurate a hygrometer as you'll find. The C200 is more accurate than any sling psychrometer.



https://www.abbeon.com/store/item.cfm?code=1577

You sure about that? In the test Hesh did the psychro-dynes and the sling by the blower were extremely close. I swung by David's shop a week or so later with my new (to me) psychro-dyne and again everything matched.

Granted, I did have one sling psychrometer that totally sucked and was way off, even when sitting in front of the intake on the blower. I did of course, buy it used. The S-P that David had again matched up perfectly with the psychro-dyne.

If buying used, I really recommend checking it against others that you know. Getting a blower of some sort helps take the readings as well.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

That sack of something is no more than plain ordinary salt. It is dampened until it is like moist beach sand. You place it in any sealed container or plastic bag and dependent upon the volume within that container and the amount of wet salt you have used, it will eventually balance the RH within to 75%...people have used this method to calibrate the hygrometers they use in cigar humidors for a long time.

It calibrates it at 75% RH. Not that useful for most builders. You really need a salt that is closer to the 40 to 50% RH that most builders use.

Salt will give a ball park of how accurate the device being tested is, you run the test 3 times and if the results show that your device is consistently low by 6% then you take this into account each time you take a reading when in use. If the rests are all over the place, send it back to China. I agree that determining the usefulness of a device this way is not a 'perfect' situation because the same device that consistently read low by 6% @ 75% RH in the salt bag may read + or - a few % at our working level of 45%, but the reality is that for most builders 5 or even 10% either side of 45% will make absolutely no difference whatsoever to the out come, what is important is that work is carried out at a 'consistent' RH more so than shooting for exactly 45%.

Sure if your winter involves ice and snow you are best to build with the RH on the lower side of 45% for obvious reasons, but over all I reckon the RH topic is a lot like using HHG, you don't need to make it that precise to work for you, there are plenty more important things to become perplexed about and over complicating things beyond their functional outcome serves no other purpose than to freak out those new to the craft.

Cheers

Kim

I agree Kim about overcomplicating things.
My motto is just build it, and see what happens.
I glued the braces on a top when the rh was probably pushing 100%.
Raining outside, moisture surely coming up through the concrete floor.
Pretty extreme situation, but I didn't know any better.
I build when I can't work, because of rain, or whatever.
That top sat for a bit, a few months, and went concave.
I glued it on anyway, and it's my favorite sounding, and looking guitar!
Big flaw though.
That's why I'm concerned with rh.
I will not be cocerned about rh being perfect, because I really can't at this time.
I'll just be more careful.