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Sizing up a Neck - quality evaluation

#22
202dy said:
Please tell us more about "roasting" necks and how that contributes (but does not guarantee!) stability.
Click to expand...

I'm no expert in roasting wood, but I have been fascinated by the process and outcomes for some time. Here's what I have learned.

The roasting of wood has been around since about 800 A.D., used by the Vikings in the building of their ships. They found that the roasted wood stood up to the ravages of water far better than unroasted wood.

The process of roasting, also known as torrefaction, exposes the wood to high temperatures in an oxygen-free environment. Removing oxygen from the environment keeps the wood from burning. The high heat causes chemical changes in the wood. First it drives the moisture content to zero. In normal wood drying, a zero percent moisture content is not desirable - the wood will absorb moisture again when exposed to a normal environment until it reached its equilibrium moisture content - that is where it is in balance with it's environment. That's because wood is "hygroscopic", meaning that it absorbs and releases moisture in relation to its environment. And that brings us to the second characteristic that roasting brings to the wood - it changes it so it is not hygroscopic. The wood no longer reacts to humidity in it's environment.

So what's the big deal if its hygroscopic or not? Well, it is a big deal. As the wood absorbs moisture, the fibres swell. And that changes the dimensions of the wood. And since wood is not a homogenous substance, the swelling will not be even throughout the mass, and this can lead to bending and other distortions. Reducing the wood's reaction to environmental moisture has obvious benefits for an instrument builder.

What's actually happening as the wood is roasted is that there are changes to the properties of the major components of the wood; cellulose, lignin, and resins. The cellulose is partially crystallized, and this is the most significant contributor to the inhibiting of moisture absorption. Similarly the lignin is crystallized and that strengthens the bonds between the wood fibres. The resins in the wood are largely evaporated and degraded in the process which increases the wood's resistance to rot and insect infestation, not really significant for instrument builders.

The reduction of water in the wood to close to zero percent moisture content reduces the weight of the wood significantly. At the same time it makes the wood more resonant, partly because of the reduced mass, but also because the water moisture acts as a bit of a vibration damper. And the strengthening of the bond between wood fibres caused by the changes to the lignin adds to the rigidity of the wood. The result is a lighter, more resonant and stiffer wood, all desirable properties for a bass neck.

I mentioned that roasting contributes, but doesn't guaranty, the stability of the wood. The reason is that to achieve 100% stability requires the wood to be highly torrefied. That would leave the wood in a state where it is very brittle and also leads to machining and gluing problems. So roasted wood is really partially torrefied wood- (fully torrefied wood is also known as charcoal). So being only partially torrefied, it only partially gains the desired characteristics. And roasting will not make a poor piece of wood into a good one. So the result is dependent upon the quality of the wood to begin with and the degree to which it is roasted. And that degree of roasting can be a tricky balance.

I have heard of some folks roasting their own wood in their kitchen oven. The process may impart a nice toasty colour to the surface of the wood, but it will really only affect the surface of the wood. Proper torrefaction effects the wood throughout, and to do that you need to maintain high temperature in an oxygen-free environment. If just the surface is treated the only benefit likely to be gained is that of the toasty colour, and to some that's not even a desirable characteristic.
 
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#24
Turnaround said:
I'm no expert in roasting wood, but I have been fascinated by the process and outcomes for some time. Here's what I have learned.

The roasting of wood has been around since about 800 A.D., used by the Vikings in the building of their ships. They found that the roasted wood stood up to the ravages of water far better than unroasted wood.

The process of roasting, also known as torrefaction, exposes the wood to high temperatures in an oxygen-free environment. Removing oxygen from the environment keeps the wood from burning. The high heat causes chemical changes in the wood. First it drives the moisture content to zero. In normal wood drying, a zero percent moisture content is not desirable - the wood will absorb moisture again when exposed to a normal environment until it reached its equilibrium moisture content - that is where it is in balance with it's environment. That's because wood is "hygroscopic", meaning that it absorbs and releases moisture in relation to its environment. And that brings us to the second characteristic that roasting brings to the wood - it changes it so it is not hygroscopic. The wood no longer reacts to humidity in it's environment.

So what's the big deal if its hygroscopic or not? Well, it is a big deal. As the wood absorbs moisture, the fibres swell. And that changes the dimensions of the wood. And since wood is not a homogenous substance, the swelling will not be even throughout the mass, and this can lead to bending and other distortions. Reducing the wood's reaction to environmental moisture has obvious benefits for an instrument builder.

What's actually happening as the wood is roasted is that there are changes to the properties of the major components of the wood; cellulose, lignin, and resins. The cellulose is partially crystallized, and this is the most significant contributor to the inhibiting of moisture absorption. Similarly the lignin is crystallized and that strengthens the bonds between the wood fibres. The resins in the wood are largely evaporated and degraded in the process which increases the wood's resistance to rot and insect infestation, not really significant for instrument builders.

The reduction of water in the wood to close to zero percent moisture content reduces the weight of the wood significantly. At the same time it makes the wood more resonant, partly because of the reduced mass, but also because the water moisture acts as a bit of a vibration damper. And the strengthening of the bond between wood fibres caused by the changes to the lignin adds to the rigidity of the wood. The result is a lighter, more resonant and stiffer wood, all desirable properties for a bass neck.

I mentioned that roasting contributes, but doesn't guaranty, the stability of the wood. The reason is that to achieve 100% stability requires the wood to be highly torrefied. That would leave the wood in a state where it is very brittle and also leads to machining and gluing problems. So roasted wood is really partially torrefied wood- (fully torrefied wood is also known as charcoal). So being only partially torrefied, it only partially gains the desired characteristics. And roasting will not make a poor piece of wood into a good one. So the result is dependent upon the quality of the wood to begin with and the degree to which it is roasted. And that degree of roasting can be a tricky balance.

I have heard of some folks roasting their own wood in their kitchen oven. The process may impart a nice toasty colour to the surface of the wood, but it will really only affect the surface of the wood. Proper torrefaction effects the wood throughout, and to do that you need to maintain high temperature in an oxygen-free environment. If just the surface is treated the only benefit likely to be gained is that of the toasty colour, and to some that's not even a desirable characteristic.
Click to expand...

In terms of stability, do you have an opinion of quarter sawn vs roasted? In researching a neck to buy, the thought occurred to me to get roasted quarter sawn but maybe I'm over thinking it. The attraction to me with roasted is increased stability, can go unfinished, and typically weighs less.
 
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#25
Wood reacts to changes in humidity, flat sawn, rift sawn, quarter cut - which ever way you cut it. But when you roast it, it changes its properties so that it reacts much less to airborne moisture.

There is nothing magic about quarter-sawn wood. Wood shrinks and expands mostly across its grain. And since it is not homogenous, like plastic, it will do that to different degrees within the same board structure. On flat-sawn wood "across the grain" is across the face of the board. On quarter sawn "across the grain" is through the thickness of the board. Regardless of whether it's side-to-side or through its thickness, the board dimensions will change with humidity, and since the wood is not homogenous, that can lead to warps twists, checks, splits etc. The real value is found in the quality of the wood and the skill with which it was cut from the tree.

But as mentioned, roasting changes the game. Roasted wood is changed so that it is much less hygroscopic, meaning it does not take on and lose moisture to the same degree through changes in it's environment. That means better stability. I suspect, but don't know for fact, that roasted wood is stiffer too which is a good feature for a neck. And I believe that a board will be lighter in weight after roasting.
 
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#27
Nicely done, Turnaround!
Wonder what would you say about my Squier's neck:
DSC_0353_small.jpg
 
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#29
If I were building the bass I wouldn't choose such a blank for the neck. It doesn't look to have all the desired qualities. And that knot in the middle. At the other hand - neck is stable enough, it has no twist, no rump and whatsoever. Seasonal relief changes are controlled by the truss rod pretty well.
Just curious - what might be the impact of such knots like the one in my bass.
 
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#30
vaesto said:
If I were building the bass I wouldn't choose such a blank for the neck. It doesn't look to have all the desired qualities. And that knot in the middle. At the other hand - neck is stable enough, it has no twist, no rump and whatsoever. Seasonal relief changes are controlled by the truss rod pretty well.
Just curious - what might be the impact of such knots like the one in my bass.
Click to expand...
Yes, right off the top that deviation on the grain of the wood in the centre of the neck is a point of concern. Also the relatively widely spaced growth rings indicate a faster growing tree, and that usually translates into lesser stiffness. The neck may be fine - the things I point out are indicators of where there may be issues, not that there ARE issues. So the neck looks to be less than ideal, in fact may be functionally less than ideal. However it may be good enough to get the job done.
 
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#31
The construction of this neck is not that simple. It has stiffening metal bars inside from 8th fret to 18th. One of them had rattling issue. And I've spent a lot of time and neck's material finding it out. Almost ruined neck's heel :) After I've finally fixed the issue - I had to do the complete fretwork to fight the fret-buzz problems both forward and backward (when the string buzzes between nut and fretted position). But since then it is stable and does the job. Besides, now I can set it up pretty low.
I have it for 5 years and I hope it has stabilized and won't go twist or rump in the nearest future.
Thank you for your valuable input :)
 
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#34
I don’t know why I missed this thread before but I will add to it. Unless you’re lucky or are looking at a high value instrument, you’re likely going to get a flatsawn or even riftsawn neck. Given those two options I look for something that’s perfectly flatsawn. The ray flecks will be on the side of the heel if it’s perfectly flatsawn (at least at that point anyways). Ray flecks are shown in the photo here. When I evaluate an instrument I always look at what kind of a cut of wood the neck is and the grain patterns.
62EE582C-2A02-4F75-ACE7-8BBFA3F3FB3E.jpeg
Luthiers working on violin family instruments seek out wood that has actually been split from the log instead of sawing it so that there is no runout and grain is straight etc.
 
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#35
1A3ECF96-22F9-4A67-A047-F88E43B94998.jpeg
Although this is a Squier,I lucked out in getting a neck that is close to perfectly quartersawn. The ray flecks are ever so slightly off dead center. Perhaps it was purposely selected because this style of neck is one piece without a separate fretboard. If you want a maple fretboard it’s probably a good idea to have it be a separate piece instead of a one piece neck to average out the seasonal movements. This neck is quite stiff.
 
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#36
Roasting wood affects it in s few ways:

Stability - a couple of things previously mentioned, plus the process tends to “anneal” the wood - if the wood is going to warp, it tends to fo it during roasting. Machining the neck AFTER that process is what gives you stability - many necks warp in their first few years; a roasted neck is already a “few years old” ( the riasting is aging in a way) before it’s carved, so it’s mostly done with its warping.

Roasted necks are indeed lighter and stiffer. Both of those changes push the dead spot on a neck higher up the neck, where it’s less obvious.
 
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#37
Fender_Bender said:
View attachment 3261121 Although this is a Squier,I lucked out in getting a neck that is close to perfectly quartersawn. The ray flecks are ever so slightly off dead center. Perhaps it was purposely selected because this style of neck is one piece without a separate fretboard. If you want a maple fretboard it’s probably a good idea to have it be a separate piece instead of a one piece neck to average out the seasonal movements. This neck is quite stiff.
Click to expand...
Yes it's showing quite a bit of fleck from the rays indicating it is quartered. But It concerns me a bit when I look at the growth ring pattern - on the upper half of the pic the rings are spaced closely together, while in the lower half they are quite wide apart. Could be just fine, but it's certainly less than ideal.
 
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#38
Turnaround said:
Yes it's showing quite a bit of fleck from the rays indicating it is quartered. But It concerns me a bit when I look at the growth ring pattern - on the upper half of the pic the rings are spaced closely together, while in the lower half they are quite wide apart. Could be just fine, but it's certainly less than ideal.
Click to expand...
The two sides are different but it’s very hard to tell even in person because the rays tend to obscure the horizontal grain patterns. The bottom grain is a little tighter above and below this area. It’s been stable in the year I’ve owned it though and as I mentioned it is exceedingly stiff.
One thing that is sure is that with continued deforestation,suitable pieces of wood will just keep getting scarcer.
 
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