Official Luthiers Forum!

Yeah, yeah.... I know not yet another "the importance of humidity control" threads but hey tis the season and in our busy repair biz we are already seeing the results of the ravages of humidity swings on guitars and other wooden instruments...

I also just read a thread about a recently built parlor that has strangely developed back back bow even when the builder observed strict RH control. Even though I know in the case of the parlor RH is not likely (but still possibe....) an issue I wanted to restart or jump start the conversation about how important it is to pay attention to humidity when building so that your creations don't grace our shop's door step in need of care to deal with cracks, poor action, sharp fret ends, loose braces, and most importantly, always....., unhappy clients.
I know that in the case of the parlor with back bow the OP said that they have their RH in check but I wanted to post this anyway because what you are experiencing with your parlor we see a lot of this time of year. And of course there are newer members here who may not have been subjected to a healthy dose of RH rant syndrome so this post is mostly for them.

Summers over, it's getting colder, furnaces are on and homes (and shops...) are drying out. Folks including our clients at times believe that they have RH control in place because they have a hygrometer, often a digital, that they rely on that says that everything is honky dory... So they or we believe that all is well until we get out our ax and low and behold the neck is in back bow, the top's dome is less than it used to be in prouder days..., and perhaps some fret ends are now proud of the neck just waiting to be annoying when the current steward plays the thing. The guitar has dried out OR was built with RH higher than the desired regional range and because of reliance on a standard, a hygrometer that is not accurate, all of this rears it's ugly head now with a seasonal change.

Last weekend I did my annual hygrometer check with my lab standard Psychro-dyne and the results were humbling... A Caliber III hygrometer with new battery read 8% low... a no name digital ready 11% high... my primary humidifier with digital display was 5% high and my Abbeon Cal that is my go-to hygrometer was 1% high indicating that it did not need calibration at this time.

At our shop my old Caliber III was also checked and was 15% out of range. I used to think that these Caliber III's were pretty good and bought three of them. My experience has been different though in so much as the CIIIs do seem to be pretty close when new but because they reply on an electro-chemical reaction over time the chemicals used seem to break down causing substantial drift that we can and have measured with lab standards such as the Psychro-Dyne. Additionally with the CIII hygrometers when new they can be pretty accurate in the range of say 40 - 50% but out side of that range the ones that I have were way off....

Most importantly though the point is that unless we have a quality way to measure RH and see how accurate or not... every hygrometer we are using really is the RH in the guitar's environment may not be what we think that it is and this includes when it was built.

Our clients tell us that they have whole house humidifiers, you know the ones that the belts or wicks get all nasty in a month and stop working.... or they have a K-mart hygrometer or this one or that one, etc. but in all truthfulness unless one utilizes testing such as a wet bulb test or other quality lab standard methods or devices you will never really know what you have and subsequently how well your instruments may hold up over time and with the abuse that most instruments experience at at least some point in their lives.

There are lots of threads on the OLF about humidity, I know long winded me participated in many of them. You will find, if interested, simple ways to know what you are dealing with in terms of how accurate your hygrometer is.

And for those who fancy building without any sort of RH control be advised your 100 - 200 hours of lovingly laboring to create your heirloom instrument may not result in the intended great instrument if the thing is sensitive to RH swings, prone to cracking or playability issues. So please as someone who has to be the one to tell Mr. and Mrs. Customer that the reason they need to pay us or someone else to repair the top crack, file down sharp fret ends, or rehumidify their instroment before it can be set-up again is that it was built without observing RH control let's get it together for everyone's sake. Commercial builders also do not need the warranty claim nightmares that result as well....

Here is a pic of my Psychro-Dyne: a couple drops of water on the wick and let it run for 5 minutes and I know what the RH is at the moment. Easy, accurate, and helps me sleep better at night knowing that my own creations were built with RH control in mind.

Thanks!

Hesh: I would love to see a picture of yourself swinging that gauge over your head...........................!! I have 4 cheapos and basically average them out................this has worked for me for a long time and was reluctant to get wet and dry bulb that had to be frailed around in the air. Think you have created a new customer for these folks. Thanks for the info.....!
Tom

_________________
A person who has never made a mistake has never made anything!!!

Yup, put away the de-humidifier a couple of weeks ago and got new filters for the old Sears humidifier. Nice steady 45-50%.
Check it every day...

Amazing (or perhaps not) but my simple homemade wooden Hygrometer has kept near perfect accuracy for going on 8 years!

I usually have both the dehumidifier and humidifier going this time of year. Weather swings quite a bit in Early Nov. Once it is steady cold, i turn the dehumidifier off.

Glenn

+1 hesh, you read my mind.Just telling the wifie this am to pull out the 2 large humidifiers this weekend.Here comes winter aaargh!

As always, RH is an interesting topic, and I will follow this in earnest. I always like to hear discussion and understanding about humidity as it relates to total water content of the air (AH) and relative humidity, which is what we usually measure. Also, the water content of wood and the shop environs, which often correlates, but is not necessarily the same as the RH. (or at least lags behind any changes)

Nature provides many reliable indicators of RH, probably the most universal and available for many is your hands, especially the eponychium (cuticles). I can't give you an exact number, but I can tell you instantly if my guitars are comfortable or not based on how my hands feel.

The most common misunderstanding I hear is when a shop is rather cool, and the RH is in the 50% range, and this is deemed OK. A RH of 50% in a cold room will result in significantly lower water content of wood than the same RH in a warm room. In the 50% RH range, this is probably ok until you get really cold temps, which may occur in intermittently heated shops. Water content of wood, which is where our concern should really focus isn't discussed as much, because you can't buy a cheap instrument to easily check it, like you can RH. At least not very accurately.

I'll be following this closely, and looking for advice on good ways to fix these problems! (besides letting the basement flood in January---been there, done that----don't recommend!)

Seems a good place to park 200$...I'd never heard of the psycho dyne before...

If you have a Samsung Galaxy S4 cellphone you have a hygrometer included along with its barometer and temperature sensors. It can be accessed and calibrated with this app: https://play.google.com/store/apps/details?id=com.aminor.weatherstation&hl=en The app gives you rh, dewpoint and absolute humidity along with pressures and temps. Make sure the phone has had a few minutes to acclimate to the room...ie not fresh from your pocket. The temperature in the shop should be where you keep it while working to get the most relative reading. (RH drops as temp goes up if no additional water vapor is added) Stay humid my friends!

Tom my friend if you want to see a pic of me slinging the Psychro-dyne over my head I likely would hit myself in the face with the thing.... Anyway the Psychro-dyne is completely self contained with internal fan and batteries to move the air. All you do is drip H2O on the wick and turn it on and in 5 minutes when it stabilizes you have a very accurate measure of RH (at that moment..... it is very subject to change from people moving around, your breath, etc...).

Hi Hans I have three Kenmore humidifiers and they are some of the best that I have used. Wish that wicks would last longer though or need cleaning less but that's very much a function of my very hard and rusty well water too I know.

Michael absolutely there are shop-made alternatives one that I know of uses a human hair and once calibrated with say a wet-bulb test they can be great. Personally I like any hygrometer that I can read at a glance say in passing so shop-made ones can be fine once they are calibrated. If you have any pics of yours please post in this thread and for folks who have made others in their shop let's see em too please?

Hey Glen - same here in the summer I have to run the noisy, heat generating dehumidifier when I'm building and in the winter I have to add water to the air but not very much in my shop built in my basement with the foundation being in sand. One of the down sides of winter for me here in the midwest is that I am schlepping water, gallons and gallons keeping my four humidifiers in my home working.... Sucks....

Hi ya Ernie and I hope that all is well with you too! Give me a call to catch up?

DNF: excellent post and you very much sound like you have a great understanding of RH, wood, etc. Looking forward to reading more from you! Most people don't understand that RH is by no means static and instead constantly changing even if not by much. Thanks for your post!

Ed buddy not sure if these things are still being manufactured but I'm posting pics below of alternatives some that can cost as little as $20 or less to make.

Below are some more pics which include my Abbeon Cal purchased from Elderly Instruments about 10 years ago. It's the best hygrometer that I have ever used and stays fairly accurate for 6 months to a year in my experience. This one has been calibrated yearly. I used to send it back to the manufacturer for calibration and they offered two levels (and two costs...) for calibration. Since I learned about wet-bulb tests though I have been doing the calibration which is pretty easy and quick too. I also like the Abbeon for that impression at a glance thing - fast and reliable too. Personally it also reminds me of a ship's clock and being an old sailor here I'm pretty fond of nautical things.

Another pic is of some of the hygrometers that we tested some years back but the real purpose of this pic is 1) to show you guys the guts of the Psychro-dynes so that you can see it's nothing more than a fancy, motorized wet-bulb test and 2) to show you the sling Psychrometer in the upper right of the pic. This is what Tom wants me to hit myself in the face with.... These units are slung around and around as the source of moving air over the bulbs.

There is pic too of two lab thermometers and a vac hose to move air. This is all you need to do a wet-bulb test and although not as fancy or convenient as other alternatives the injury rate is lower.... while having excellent accuracy. After moving air over the two bulbs, one wet one dry AND with the wet bulb closest to the sucking air source or further away if it's a blowing air source and Googling wet-bulb chart you can tell what your RH was while doing the test.

Everyone else if you have a method, device, etc relating to RH control and guitar building let's see em please?

Thanks!

One of three that I made around 8 years ago. I use it as a stop-go traffic light type signal. Between 6 'o' clock and the immediate marker to the left indicates that things are fine.
How do I know that it is accurate? Well I have two digital Hygrometers that read within a few percent of being correct in the Pot. carbonate test. I also have a sling psychrometer.

Very cool Michael! This is exactly what I would like to have too for that impression at a glance thing.

Nicely done and thanks for posting a pic.

Are all electric hygrometers about 10% low?

I have found that here in E. Tennessee I don't need to humidify the shop in the winter as long as I don't let it get much above 60F. Humidity stays around 40%. I don't mind working in the shop at that temp in winter. Finished guitars are in a closed room in the house that has a stand-alone humidifier so it's easy to keep it at 40-50% except for filling the water bucket and changing the wick.

For summertime I have a dehumidifier in the shop with a drain going to the outside.

I have an Abbeon in the shop just like the one Hesh showed and a sling psychrometer to check calibration.

_________________
Steve Smith
"Music is what feelings sound like"

Joey we've tested every digital that we can get our hands on and they read all over the place. David Collins took one of our CIIIs apart last week to see how it worked and also to see if he could calibrate the thing since it was 15% off in the desired range...

I was working on a guitar and looked up at what he was doing about 1/2 an hour later and he had rigged up a CTS pot to the CIII after figuring out how the sensor (electro-chemical) worked. Although the pot did not help the thing in terms of an ability to calibrate the sight of this little hygrometer with a CTS pot now attached to it had me laughing my arse off... I'm always thankful that David is on our side...

Steve nice combo and it's all you should ever need for RH measurement.

Regarding temp and RH there is that interplay/relationship that David F. shed some light on for us earlier in the thread. I like my shop at 72F first because my comfort is pretty important to me.... and second because many of the things that we use such as finishes, glues, etc. can have issues curing in cooler temps. Since we use HHG frequently too the warmer the longer the already short open time is. There is a reason why some of the violin guys have hot rooms, closets kept at around 100F to extend working time for difficult glue-ups.

What Steve and Michael are doing/have done is a great way to go with either a commercial, quality hygrometer such as the Abbeon or a shop-made creation when in both cases both Steve and Michael have a wet-bulb-type method to calibrate and know what they really have.

For some of the newer builders there are countless threads here on the OLF describing what happens when RH control is not observed so hopefully something here will be helpful to many and maybe just maybe help you guys produce better guitars that can stand the test of time. If you ever have the opportunity to visit say Taylor or Martin and get to ask them about their environmental controls and systems you will quickly learn that major manufacturers have spent likely millions to date to control RH. I also know that both Yamaha and Steinway also have fairly elaborate environmental controls at many stages of production.

A quick and inexpensive way to address RH for hobby builders is to purchase two lab thermometers (around $20) and learn to do a wet-bulb test. Then purchase any hygrometer that you wish including inexpensive ones and compare it in the desired range say 40 - 50% and see how it does. Repeat a few times over time and then note on the hygrometer the error (Sharpie is your friend).

I just purchased yet another humidifier that is rated at 2,000 square foot and the seller also had cheap, mechanical hygrometers so I picked up one of those too for some testing. The hygrometer was $8 and so far it's actually pretty accurate. If it does well over time I may post pics and nomenclature so that others can get one too but it has to pass the testing first.

Mike N--that is beautiful. Any info available on construction methods/materials? I'd love to try one of those! BTW, I visited your website, and was blown away with the beauty of your instruments! The clip was especially beautiful. My wife stopped in her tracks and wanted to know what that was.

Here's my home made hygrometer, which has inaccurate numbers written on it:


Photo taken in June, which is about as wet as it gets indoors. Now it's bent just as far the other way I do love the visibility from a distance.

The digital on the right is one of these calibrated hygrometers from David Burgess http://www.burgessviolins.com/products.html, and I had been calibrating my wood one off that, but then they never seem to agree later. Not sure if it's just a matter of response time between the two or what.

Construction of the wood ones is extremely simple. Just glue two strips of spruce together, one long grain and one gross grain, and plane/sand it thin enough to flex easily. Then attach one end to something, and anything else is just to fancy it up or make it more readable (numbers, or dots like Michael's, as opposed to just looking at the curvature). The humidity at the time you glue the strips determines the center point, so gluing it in 40-50% is good.

I've been building in low humidity (30-35%) the past few years, and those instruments seem to tolerate the full range here without any control at all. Sometime I need to take one to a tropical climate for a couple weeks and see if anything pops Flatsawn ebony might, but I'd doubt it with quartersawn spruce/rosewood/mahogany.

I test my Abbeon with a dry bulb / wet bulb set up like Hesh shows a few post up using the shop vac. I just use one thermometer though and write the dry bulb reading down prior to taking a wet bulb measurement.
I then use this calculator from NOAA to get the RH: http://www.srh.noaa.gov/epz/?n=wxcalc_wetbulb
Notice it needs the barometric pressure, it can make a difference of a few points. It can be hard to find an accurate pressure as they appear to normalized to sea level. For example weather.com list my atmospheric pressure at slightly above 30 inches of Hg, basically the same pressure they give Berkeley CA. The only problem is I live at 7,000 ft and Berkeley is at sea level. My actual pressure is about 23.5 inches of Hg, thanks to the National Lab in our town.

_________________
Jim Watts
http://jameswattsguitars.com

Re. The wooden Hygrometer. The 'indicator' on the type that I made are 15 inch x 1/2 inch although these measurements are hardly critical. I actually use two different types of wood, one long grain the other end grain. The end grain on mine just happens to be Sapele but only because I had it to hand. My end grain pieces are 2.5 mm, the long grain 1.5 mm thick.
I tried a cross grain indicator and whilst it certainly worked it didn't seem to be quite as sensitive.
It's probably best to glue the end grain to long grain pieces in your 'target' humidity. That way the indicator should point near vertical whenever the room is at that particular humidity. Use epoxy glue, as water based glues really upset the position of the indicator.
Obviously these things work because it's wood reacting to changes in RH - that's what our Guitars do!
The reaction time is obviously a little slower than digital or hair Hygrometers, mine by around 30 minutes. That is nothing to worry over.
You will need to check from time to time that they are still working accurately. They should be fine for a few years at the very least. As soon as mine starts showing signs that it's no longer reacting correctly I'll just make another indicator. It's not as though they are a lot of work.

I just got an identical unit from eBay for $30. Works perfectly after taking ten minutes to clean an oxidized battery terminal. Shop is a perfect 50%. My humidifier it set to maintain 55% and my two digital hygrometers read 45% and 50%.

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It will probably be alright.

Ed, go on Ebay.ca and search for the Psychro-Dyne Psychrometric. I found one in the states dirt cheap, with shipping of 30 bucks to Windsor. There is one in Saskatchewan going now for a good price. I have 2 Abbeons, and a Caliber III that all stay within a few points.

Bob

I have a wet/dry bulb with a small fan set up to blow across it from the dry bulb side.
I have a chart hanging on the wall beside it.
Working in celsius the math is simple, wet bulb 18 dry bulb 11 18-11=7. my chart says 41% RH.
I'm wondering if I really need anything else?
Or am I missing something?

_________________
Say what you do, Do what you say.

Good going Bob - you should be all set now and with the Abbeons that in my experience have very minimal annual drift your set-up sounds great!

Dave you have all you need too with the wet/dry bulb stuff. The only suggestion that I would make is to add a cheap hygrometer, even a digital, and use the wet/dry bulb to see the error in the digital and note same. I would likely do this about three times over a couple of weeks to make sure that the digital is stable in it's error rate. Once you know what the RH really is via the wet/dry bulb I would put some tape on the digital and note the error. I have digitals all over my house and they all have a piece of tape on them indicating the error such as "reads 8% low" etc. This will give you the RH approximately at a glance without having to get out the wet/dry bulb and play Bill Nie the Science Guy every time you want to glue two sticks together.

Just...........................a six pack of Keith's and a .......!!!
Tom

_________________
A person who has never made a mistake has never made anything!!!

I believe your wet bulb should be 11 and your dry bulb 18