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Hello All,

Well, let me first say, that I apologize, for ever starting the topic several weeks ago, “Is humidity really an issue”.

They say “experience is the best teacher”, and I got a big dose of it lately!

Recently I started a topic “Planning my next build!” which I got some good advise on where to go
with wood choices. JJ Donohue brought up a point that got me thinking, so, I posted a few pics
of the top & back set in question with edge views. That’s when the lesson began! It didn’t take
long for Don Williams, and Hesh to realize what had happened to the top & back! Yep! You guessed it!

TOO MUCH HUMIDITY!

So, at the request of one the OLF tutorial masters “Hesh” and, after buying a new de-humidifier.
I’m recording the process of getting my shop to an acceptable RH.

Starting at 80% humidity, and though only just over 24 hrs. I thought you might want to see what
I’ve got so far. It’s amazing to me that in just 24 hrs. there have been very noticeable changes.

I lost the first pic of the new de-humidifier when I first turned it on, but, it was set to 45%RH
and the actual humidity was reading 70%RH on the de-humidifier it self. This at first was a little
confusing, because my other humidity meter that I keep on the bench was reading 80%. Things
did seem to even out after 24 hrs. had past. And, I suppose that will continue for several more days.

The first pic is a log I started. The rest are in chronological order with titles corresponding to the log.


The Log



Humidity Meter



Top at 80 RH



Top side view at 80 RH




Back at 80 RH



Back side view at 80 RH



Humidity Meter



Top at 38 RH



Back at 38 RH




Humidity Meter




New dehumidifier




Top at 40 RH



Top side view at 40 RH



Back at 40 RH



Back side view at 40 RH





If you got'em ask'em!

Robert

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Everything has beauty, But, not everyone see's it!

best investment ever eh? Now if I could just get a large humidifier for the winter....

wow man, that is crazy! what a huge difference. i also have been wondering about humidity for quite some time. like you mentioned, is it really that big of a deal? well, i guess we know the answer to that! i recently bought a digital hygrometer, and while im not sure of the precision of the intrument, the readings that i found in my house and shop were pleasantly surprising. inside my house with the a/c set at 78 degrees, humidity has stayed between 39% and 43% in a 48 hour period. not bad. outside is a bit different. temperature ranges from over 100 degrees in the day to around 80 over night. humidity fell as low as 30%, but i guess thats better than 80%! im glad you got your humidity situation all figured out. thats pretty exciting. now happy building!

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sweat the small stuff.

Congratulations, Robert! I commend you on collecting the data and posting the results. You're now an expert because you have hard evidence.

The other issue now is to make sure you glue braced and voiced plates as soon as possible. That means making up the rims first. Lock in those domes before they have a chance to flatten out.

Happy building!

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

experience is indeed the best teacher. i know you were told by a lot of folks that it mattered, but it is hard to believe until you experience it.

perhaps more of the new folks in the game will profit from your experience since you had the great idea to document your changes so very clearly. the old adage about a picture being worth a thousand words will hopefully come into play.

the effects you illustrate so well continue to happen when the rh goes to low as well, sometimes causing braced tops to evert their dome.

and the effects continue even though the box or instrument is complete. managing the rh your instruments live in will enhance your playing experience as well as help ensure a long uncracked, unwarped musical life for the instrument.

at the same time, surprise, surprise, the range wee desire for our instruments is also the most healthful and comfortable rh for humans as well!

so the effort can be justified to all in the family as your taking care of their well being as well. a win/win situation!

Thanks for posting the pics demonsrating the effects of humidity on tops and backs. I also had to learn the hard way a couple years ago. Big surprise, huh?

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Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

This is your plate. This is your plate on humidity. Any questions?

Nice pictorial Robert. I cast my vote for putting this in the tutorial archive.

Bob

This certainly should go in a FAQ section if we had one. Maybe with the new software we can have a FAQ section.

Robert, it's really amazing isn't it?

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Hello All,

Thanks for all the positive comments guys!

And, I sure hope that other OLF’ers do get out of this what I did!

The following is an update, and just a little over 24 hrs. from the last set of pics. I’m thinking that
this set of pics will be all that is necessary to follow up on, since there is very little change, if any.
If I notice any significant changes over the next few days, I’ll be sure to post them.

Unfortunately, there may still be a problem with the top. It seems to have become slightly concave.
The opposite of what it was at 80% RH. Maybe it’ll straighten out over the next few days.

Here are the updated pics


The Log Updated




Humidity Meter




Top at 40% RH July 10, 2007




Top side view at 40% RH July 10, 2007



Back at 40% RH July 10, 2007



Back side view at 40% RH July 10, 2007




Thanks Looking,

Robert

_________________
Everything has beauty, But, not everyone see's it!

Robert...here's a thought to get the dome back.

Slightly dampen the surface and gobar clamp it into the appropriate radius dish for a day or 2.

Once removed from the dish, immediately glue it to the rims.

I have never had to try this but it just might work...and if it doesn't you can always remove it and go to plan "B"

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

Hi folks,

This is a very interesting thread. I have thought about the great pics Rob has shown us and I want to do a consideration. Bear in mind that I haven't built any guitar yet, however to me it appears that when the guitar is assembled it is more dangerous a low level of humidity rather than a high level. In fact, while in a high humidity environment the sides prevent the top and back from assuming the convex shape shown in the pics, if the humidity is very low they cannot prevent them from assuming a concave shape and this may lead to a crack. What's your opinion on this?   

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Andy

Italian spruce if you look for the best!!

Robert - Thanks for sharing that with us.  I am getting ready to set up my shop in a large garage by closing in a section.  I live on the Gulf coast of Texas where right now the temp is in the 90's and the dew point in the upper 70's.  This translates to a relative humidity of about 70%.  In the mornings it is close to 100%

The garage is currently unconditioned and I store my wood in the house with central heat and air.  I keep the RH at about 50% in the house. 

I am going to build my shop with humidity control in mind.  I'll have to get an A/C/heater unit that also controls humidity.

On your top and back I do hope that you won't have to scrap them.  The idea to put them on a radius board with go-bars and adding moisture (distilled water wiped on very conservatively) sounds good.

Would anyone be interested in a discussion of relative humidity as it relates to wood?  I can add some from an engineering viewpoint relating temperature and humidity.

I have a similar situation as I live in high humidity.

I have a "problem" which is too much wood and a 3000 sq ft shop and it will be impossible for me to insulate/dehumidify the whole shop so I will also partition out a work/room of about 300-400 sq ft to control humidity and temp.

So my question is (without starting another thread) what would be a safe or most efficient time frame to transfer the seasoned materials outside of this room to it's new invironment before building and, can it leave this environment to do some detail/rough work for short periods of time and then returned without compromising it's working intergrity? Keep in mind that I will have to choose a select amount of wood at a time with will be the next instruments to be built. Also, what assembly/finish stages would it NOT be a good idea to take it out of that room? My tools and work stations are spread out throughout the shop and have to keep the absolute minimum of tools and storage in this room. I know a lot of the raw stock I have right now is very stable in it's normal invironment and can I work these pieces (components such as neck stock, fretboards, plate jointing, rim assembley etc.) to a certain stage before commiting them to that room? Since I don't have that room made yet, I will start making whole instruments anyway so I can get my feet wet as I have not made any instruments and have only started to resaw back/side sets etc. and hope it stays together or does not pose that much of a problem since the finished instruments will stay with me at my place.

Thanks

ckp

Hesh,

I will try the calibration thing, and let you know how it comes out. As for your 2nd point, John Watkins
built that set, and as you have said, he probably did build them at 45-48% RH. I would call him,
but, the last time I spoke with him, he sounded very busy with trying to catch up on orders.

JJ,

You’re not going to believe this, but, about an hour before I read your post I was thinking of
doing exactly what you suggested! I believe that will work! I may just do it any way, because the
top is ever so slightly wavy. I’ve got some preparation to do first though. I will calibrate first,
then I need to get a radius dish, I’m still waiting for a OOO mold to be delivered, and I still need
to get out to my old shop and cut up a set of sides, out of a 3"X6" piece of mahogany.

Andy and Steve, Welcome to the OLF!

Andy, I’m still learning about this humidity thing, but, I believe you’re on the right track, in that,
LOW RH is much worse than HIGH RH.

Steve, if you search the archives, you’ll find many threads on this subject. Several of them are
quite interesting and get a little technical. Probably, right up there in that engineering point of view
your looking for!

Thanks All,

Robert

_________________
Everything has beauty, But, not everyone see's it!

Ckp,

My advise is the same as to Steve, look through the archives, or start another topic. There are a lot
of seasoned veterans here at the OLF, that have had much experience with this issue, and my guess
is they would be more than happy to help you with your decisions.

Robert

_________________
Everything has beauty, But, not everyone see's it!

looking at the top it appears that it has been built with the transverse braces straight, whilst the x and lower bout braces were radiused. check with john to see if that was the case before you take any further action other than getting your rh back up to the 45-48% range.

and andy, as i said in my earlier post in this thread, overly high or low rh will affect the assembled box just a it will the plates illustrated here.

tops will rise in high rh raising actions and making the instrument uncomfortable or unplayable, and low rh can cause the tope to sink, even go concave, lowering action, result in buzzes, and even pull itself apart. these facts have been long recognized by builders and the major manufacturers now emphasize humidity control as essential to good maintenance.

taylor was probably the first major maker to really publicize the need for rh control, and have a lot of good information on their wed site.

Hello All,

OK, this is kind of an update. I got to thinking about my ceiling in my new shop, (pic below) they
are the standard drop ceiling tiles. What they are made of I’m not completely sure of, however,
I would think some kind of paper product and fibers. One thing I do know, is they are very absorbent.
I’m guessing that these ceiling tiles are in a constant state of humidity changes, since it is
80% RH above the ceiling, and at least ? that in my shop. So, I thought I should get some plastic,
and line the top side of the tiles in order for the tiles stay at the RH of my shop. What do you think?

Also, after reading the link that Hesh posted, I got started on the salt test for my (Lowes bought)
hydrometer (pic below). I’ll let you know how that works out.

The last pic, I think is rather interesting. In the link I just mentioned, I saw where Hesh put all 3
of his hydrometers together, so as to compare their readings. I put my hydrometer on top of my
de-humidifier early this morning, and.... well you be the judge!

Michael,

Good advise sir! I guess, I should at least try and get in touch with John before I attempt anything.
BTW, did you know that MAGI is having another small gathering this Saturday in Charlotte, NC.
I’m sure everyone would welcome your presence. Let me know if your are interested!

Robert

_________________
Everything has beauty, But, not everyone see's it!

i wouldn't worry about the ceiling. my air conditioning system and my old dehumidifier has little trouble keeping my wood room around the 45-47% mark. the only time it goes higher is when we have a major cloudburst, like yesterday evening, but this a.m. it was back to where it should be. the general workshop area takes a little longer.

unfortunately i was unaware of the magi meeting, but alas, once again would have been unable to accept even if i had known of it due to long standing prior commitment in blacksburg, va. maybe next time!?

Hello All again,

This I believe, should be the last update.

There is no change in the top & back set.

The salt test is complete. Pics below!

Thanks to all for your participation!

Robert


After 3 Hours



After 16 Hours

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Everything has beauty, But, not everyone see's it!