Relative Humidity

Chasplaya
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Sat Jan 16, 2010 2:42 am

This Christmas I got a gift of a Weather station with built in Hygrometer, as such I have done a little bit of research on the subject and found the following list.

I know some of you don't prescribe to the humidity issue and to be honest it's not something I thought of much before I got the Weather Station. My guitar room so far this summer has been between high 30%'s and low 50%'s

http://www.totallyguitars.com/images/fb ... Guitar.doc


BigBear
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Sat Jan 16, 2010 3:00 am

Chas- while some of that article is factual it really ignores the basic physical characteristics of wood. To suggest that a 10% differene in humidity will have such a huge impact on a guitar is just silly.

The reason a guitar plant would keep their humidity at 45-50% is because that would be a good average humidity for most home, as witnessed by your home. Mine is about the same. So it makes sense to build the instruments as close to the same humidity as they will be spending the rest of their lives.

I believe the only place that humidity will impact a guitar is between dissimilar woods, like tone woods and bracings, or fret boards and necks. And some glues, although not most modern adhesives, may be subject to increases in humidy but not decreases.

This is where folklore has overwhlemed logic, common sense and science!


Chasplaya
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Sat Jan 16, 2010 3:16 am

Taylors response to several questions from their FAQ's pages: This takes you to a link page to several PDF's about Humidity amongst other issues. Taylors have more to say about humidity than most other manufacturers that i've seen.

http://www.taylorguitars.com/guitars/re ... heets.html

Bear your comments are placing your commission in jeopardy lol!!


Chasplaya
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Sat Jan 16, 2010 3:27 am

Bear somehow I just knew you would comment. Personally I have never experienced a problem. Nor do I know of anyone who has, that is to say with humidity alone. Problems with leaving guitars in car boots now that i've heard of even here in NZ where necks have warped beyond recognition.

So its an interesting topic obviously this is an issue where you have two perspectives generating healthy debate! SOme will be hot on the topic others cold...


BigBear
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Sat Jan 16, 2010 4:04 am

Chas- that's a really interesting article and consistant with what's been said about humidification in guitars for years.

As an applied scientist I am innately skeptical of anything that runs contrary to natural physical laws. I would ask Taylor (or anyone else) some questions:

1. How many guitars do you see showing the effects of lack of humidity? (I'll bet this % is extremely low)

2. Of those that do show some distress, is lack of humidity the only possible cause? (ruling out abuse, or dramatic changes in temperature or humidity)

3. What is the relative moisture content of all the woods that are used in Taylor guitars? What is the acceptable variation in this range? (ie. could variations in the wood be the cause and not just humidity?)

4. Are different woods used in the guitar installed at different relative humidities? (ie. is the ebony in the fret board the same humidity as the spruce top?)

5. Since shrinkage in wood occurs laterally (cross grain) versus longitudinally, are all the guitars exhibiting dry shinkage problems only moving in this direction and if so, what percentage change in width will cause a problem?

6. If 47% is the ideal humidity for guitars, what is the effect of too much humidity and has anyone ever seen a guitar that exhibits excessive moisture problems? If not, why not?


I'm not suggesting that humidity should be rejected as a problem in guitars. I am suggesting that the problem is grossly overstated, under-researched and poorly understood. I have never met anyone with dry shrinkage problems in their instruments. I just wonder if all the hype is warranted for a very small problem?


Chasplaya
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Sat Jan 16, 2010 4:17 am

Bear you make excellent points and you are obviously better equipped to comment than I. I would be most interested in the TG community views I guess we would get a mixed bag; those on the fence and those on one side or the other.


AndyT
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Sat Jan 16, 2010 5:53 am

My wife's Ukulele was left in out trunk (Boot for Chas), and due to heat and humidity, the bridge came unglued and snapped off.

We took it to the factory here and they gave her a choice between 3 slightly more expensive Ukes to replace it. She picked a beautiful Solid Koa 8 string Baritone Concert by Pono. Exceptionally nice Uke. The guitar equivalent would be maybe a $3,500 Taylor.

When I asked why it came apart, he told us it was the glue they used. "We still use old fashioned wood glue." he said. It's proven and we prefer it over synthetic glues. He had some more reasons why they use 'Elmers' wood glue, but it was rather technical and had to do with stuff like it doesn't block pores and other stuff like that.


reiver
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Sat Jan 16, 2010 7:51 am

Just FYI.

From Wood & Steel, Fall 2008, ('Bob' is Bob Taylor)

With traditional seasoning
methods, Bob says, a guitar top
that goes from an environment with
50 percent humidity down to 30
percent will shrink almost three
millimeters in width — almost 1/8
of an inch!
“That’s putting a lot of strain
on the guitar when it’s doing
that,” he adds. “We’re trying to
get it really small and bring it
back up. Our approach will
make it shrink about one or
two millimeters instead of three
in that situation. It makes a
big difference.”


The approach that he mentions is to pre-dry wood from its starting moisture content all the way down to 0%, then it's re-hydrated at 47% RH to a moisture level of about 6%. They feel that this better prepares the wood for the conditions in which it will eventually find itself, ie a dry music shop.

Could this be why Taylors sound good in the shop?

r


tom18
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Sat Jan 16, 2010 8:49 am

Chas,
Timely subject. I don't have a hygrometer in my home but I know the average RH is fairly low here (NJ) in winter. When I bought my guitar I was also sold a device that mounts over the sound hole and holds a moistened sponge within the guitar. It always seemed to me that this only partly addresses the problems low RH may cause; it certainly does nothing for the fretboard. Any advice from other members would be welcome.
Tom


AndyT
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Sat Jan 16, 2010 9:01 am

Ok, we are talking RH here for guitars. But Guitars are played by people and generally speaking the best humidity levels for people are actually from about 55-57 to around 68-70. So what is that going to do to the guitar?

Most Central air systems I've seen are designed to maintain RH levels in that area. My brother does HVAC for a living so I guess he should know.


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