Changes in Humidity vs Wood Quality.

[SamBooka]

So I was sick this week.. didnt play much.

The past couple of weeks winter really kicked in here.

Picked up my gibson and noticed I had to tighten the trod a bit (well more than a bit.. 1/4 turn)

That got me to wondering. I have a couple other guitars that were fine.

Why are some necks more affected than others? Type of wood? Quality? How long/well it was aged? None/All of the above?


Just curious.

Drew

[PTChristopher]

Answers in my opinion:

>>> Why are some necks more affected than others?

Mostly due to the type of wood, but there are other factors.

>>>Type of wood?

Yep. Wood swells and shrinks with changes in moisture, mostly on the tangential and radial axes, but there is also a very small change in the longitudinal axis - which for our purposes is from the nut to the bridge.

The tangential and radial axes are far more important for most applications, so you'll find data for these rates for most types of wood. Nobody in the real world cares about the longitudinal axis.

My favorite sad movie is "Longitudinal, the Unloved Axis" - Spanish actress Natalia Verbeke was superb as Longitudinal's girlfriend.

But I digress,...

In the case of a guitar neck, the main issue is the difference between longitudinal (sniff, sniff,...) changes in the neck wood vs. the fingerboard (FB) wood.

and, that the FB wood often reacts more quickly to ambient conditions.

To make a long story short (OK, too late for that.), Ebony FB's tend to move more than Rosewood. So an ebony FB on a long neck (many frets clear of the body) will often need more seasonal adjustment.

It gets dry and the ebony FB shinks longitudinally more than the neck wood - you adjust the rod to get the relief back to where you want it.

There are always exceptions. It is wood and is subject to considerable variation from one piece to the next.

>>> Quality?

In my opinion this is not a practical issue. It may be fun to dump on one's un-favorite brand, but it does not drive any useful action in my opinion. We should bark up (longitudinally) some other tree.

>>> How long/well it was aged?

Any issue with the seasoning of the wood will have sorted itself out (for better or worse) before you get the guitar. I am not at all compelled by the anecdotal evidence of any general trends based on the seasoning of the wood once the guitar has been around for a few months. If the wood was poorly seasoned and goes nuts, it happens fairly early in the guitars life.

Yes, there are exceptions where some wood will go rogue after a few years - but again, this is part of the normal variation in wood as a commodity.

>>>None/All of the above?

Well, there is also:

- The density of the specific piece of wood used in your guitar.
- The type of any extra reinforcement (carbon fiber is the modern reinforcement).
- The overall compression on the neck via string tension and the type of truss rod. A dual action truss rod does not squish the neck the way a good old fashioned rod does.
- And probably another thing or two that do not come to mind at the moment.

Still all in my opinion.

EDIT: It is possible to really roast wood to the point that the resins are affected to a practical extent, and this can affect not only overall stiffness, but also the shrink rates. Bamboo fly rod makers use this to their advantage (OK bamboo is grass not wood, but the principle is the same.). But, this sort of heat treatment is not a practical issue in the preparation of the woods in our guitars.

Chris

[SamBooka]

Thanks Chris!

I am comparing a 96 ES165 and a 64 ES125.

It isnt about dumping on our favorite whipping boy Lets leave that to the other threads.

The 165 also is more tempermental when it comes to tuning (it goes further out of tune on a day to day basis than my other guitars)

It doesnt bother me.. I am not going into the old vs new thing since I dont play the 125 nearly as much as the 165 (which sounds better and a nicer feel to the neck).

Thanks for the reply

Drew

[Snap]

How long/well it was aged?

For me this is the only important factor along with good wood selection. More how good wood was seasoned than how long. It doesn't take too long actually. And of course wood selection. Regardless of the fame or brand name, factories don't do that, or at least not as good as individual luthiers will do. Luthiers don't use unstable wood blanks for their necks. Factories do it.

Anyone believes that the adjustable truss-rod were invented in order to deal with seasonal changes? Not at all. It was developed back in the day to save production costs. Loads of woods were discarded at Gibson by the time. This system allowed to use less than optimal woods to make necks, thus saving money. Now it's mandatory for for every modern guitar. And most guitars need that stational setup. All my '30s guitars with duraluminum reinforced necks (non adjustable) never suffered of any seasonal change. The classical guitars a friend luthier makes since 50 years ago using well seasoned and thoroughly selected (non reinforced) cedar never suffer of any seasonal change and they never develop a bow along the years. Now think about it.

[PTChristopher]

Hi Snap,

I enjoyed your post and really appreciate the very interesting angle you take on this fun subject.

Surely you are right that there are many very caring luthiers who make what they feel is very good wood selection. "Good" might benefit from some definition, but your point is very clear and surely shared by many.

I think there may be some breakdown in the actual motivation, cause, and effect regarding the development and use of adjustable truss rods and the economics of manufacture.

But I share your experience that some non-adjustable necks with significant reinforcement do quite well as humidity changes.

And the stability of very wide cedar necks on very low tension nylon string guitars is indeed a fine thing.

Nonetheless:

- Wood will eventually get to a moisture content level that is driven by ambient conditions.

- As these conditions change, the moisture content of the wood will change - with no regard for the wood's particular moisture content at the time of manufacture into guitar-shaped stuff.

- Laminating (FB to neck for example) woods with differing longitudinal axis expansion/contractions rates will result in some tendency for the neck to move back and forth with humidity change.

- This happens with seemingly no regard for the state of mind (or state of grace) of the builder. But there is considerable variation from piece to piece within a species (I think "American Idol" supports this view.), and sometimes this variation can become attributed to the process of manufacture.

But to beat the bushes just a little more and look for holes in my simple[ton] summary:

There is no question that some care in wood selection (grain orientation, density of a specific hunk-o-wood, and degree/method of seasoning) can have some impact on the eventual performance of the neck through humidity changes.

But this is wood, and there are many "outliers" in terms of eventual performance of a guitar neck. I have found it very helpful to take care about expanding some pleasant (or unpleasant) specific experiences into broad conclusions.

Thanks again for the post and some give and take on the subject.

Chris

[stevedenver]

there are many factors, including the inherent moiture content of any given peice of wood, as well as wood grain


simply, a critical factor is seasoning wood-
wood used to be seasoned 10 years or more
kiln drying now does most of this

i know of one high end maker in CA that has all his wood age after purchase for 2 years -because it settles and problems show up
it is interesting that collings (and im sure others) have strict humidity control in the factory-but ....i suggest that this may not be good for the end user once that instrumnet is built, under tension and in the consumers hands-then the humidty changes again and probelms show up-for some reason seasoned wood seesm to have greater 'elasticity'-not literally, but the ability to tolerate changes

the note of reaching ambient moisture i think is accurate, and this is why i only wood that has existed as instruments for at least 2 years, things tend to bend and warp and crack within that time -not that they cant later, but most stuff shows up

but simply, there is a period of time in which wood settles and stabilizes

i live in Colorado, i keep my instruments in the case when im not playing ( to act as a buffer to temp and humidity changes-simply to slow them)

its fairly dry here most of the time, but we do get a wet season from time to time

i have not experienced very much in the way of changes, be it maple, rosewood, ebony, mahogany in any of my instruments-but there is some and this is why i do oil boards and bridges about 2x per year-it slows the moisture transfer as well as directly adds to the wood

as for the difference between fingerboard and neck -i think its technically accurate, before the use of truss rods, frets actually were used to help to stiffen the board (by pressing into the wood and pushing it outward longitudinally)-

now - i would think that the truss rod counters this for the most part, but not entirely-

[stevedenver]

[quote=stevedenver;197650]there are many factors, including the inherent moiture content of any given peice of wood, as well as wood grain


simply, a critical factor is seasoning wood-
wood used to be seasoned 10 years or more
kiln drying now does most of this

i know of one high end maker in CA that has all his wood age after purchase for 2 years -because it settles and problems show up
it is interesting that collings (and im sure others) have strict humidity control in the factory-but ....i suggest that this may not be good for the end user once that instrumnet is built, under tension and in the consumers hands-then the humidty changes again and probelms show up-for some reason seasoned wood seesm to have greater 'elasticity'-not literally, but the ability to tolerate changes

the note of reaching ambient moisture i think is accurate, and this is why i only buy 'wood that has existed as instruments'-ie guitars, mandos etc for at least 2 years, things tend to bend and warp and crack within that time -not that they cant later, but most stuff shows up

but simply, there is a period of time in which wood settles and stabilizes

i live in Colorado,

i keep my instruments in the case when im not playing ( to act as a buffer to temp and humidity changes-simply to slow them)

its fairly dry here most of the time, but we do get a wet season from time to time

i have not experienced very much in the way of changes, be it maple, rosewood, ebony, mahogany in any of my instruments-but there is some and this is why i do oil boards and bridges about 2x per year-it slows the moisture transfer as well as directly adds to the wood

as for the difference between fingerboard and neck -i think its technically accurate, before the use of truss rods, frets actually were used to help to stiffen the board (by pressing into the wood and pushing it outward longitudinally)-

now - i would think that the truss rod counters this for the most part, but not entirely-