What is the most chatoyant wood?

[chatometry]

Hi everyone
This is Paolo, from the www.chatometry.com team.
I just wanted to share something about what we've been doing last years, that is trying to answer to the above question. Basically, we identified a reliable method to measure wood chatoyance, which is the way many wood species shift their color depending on the lighting direction.
This is a common example (european walnut); what you see is a sequence of 36 pictures showing the same piece of wood (sanded to 1500-grit with no finish) lighted from different directions:

Now the useful info: we put together a summary table based on thousands of samples, showing the typical chatoyance value of many wood species - here:
https://www.chatometry.com/woods/Each wood can be clicked to reach its specific page, which shows some example of chatoyance on that wood.

We tested 105 species out of the thousands and thousands growing around the world, so there is still much to do...

I hope these data can actually help some of you
Paolo

 

[Fitzroy]

Fascinating, thanks for sharing.

 

[rogxwhit]

Chatoyance: having changeable lustre.
C18: from French, from chatoyer to gleam like a cat's eyes

It is a fascinating effect but I have often regarded it as a nuisance especially when trying to match boards in a piece - it cuts the options down - as if life wasn't hard enough already!

 

[Sandyn]

I have seen that effect, but had no idea it was a recognised property of wood. Fascinating. Thanks

 

[chatometry]

It is a fascinating effect but I have often regarded it as a nuisance especially when trying to match boards in a piece - it cuts the options down - as if life wasn't hard enough already!

I heard this from many people
What is your solution?
Matching the grain direction? Choosing a finish that inhibits chatoyance? Choosing a low-chatoyance wood?
Paolo

 

[rogxwhit]

No the wood species for a project is imposed beforehand. And one may have a limited supply - if it's not from stock one often buys just enough. My answer has always been to orient the boards available so as to cause the least disturbance. It can be a compromise sometimes in the real world.

 

[Droogs]

It can be a nightmare when bookmatching. Most often seen on mass produced guitars and violins etc, I was suggested to me that it is perhaps caused by the direction and sharpness of the tool used to cut or slice the wood. This was suggested to me when I was learning about marquetry and veneering furniture panels by my old master. he pointed out that sequential leaves of veneer would have a similar chatoyence as they were composed of similar enough fibres but that the need to flip over a leaf in order to bookmatch would mean that the fibers were orientated in a different direction or angle in relation to the angle of the cut and therefore reflected light at opposing angles.
I have often thought about an experiment where the direction of cut for each slice of leaf of veneer would be at 180 deg to the previous. IE if first slice is an up-cut then rather than having the veneer slicer continue round for another cut in the same direction it could be reversed and give a downward cut. Obviously you would need a double bladed machine.

Also the fact that on most industrial veneer slicing processes the knives only give a clean "true" cut to one surface. Especially on rotary cut veneer such as for panels, where the underside face of the cut gets badly crushed and cracked compare to the top surface of the veneer.

 

[Droogs]

Although I say it can be a nightmare when trying to stick 2 bits together the effect itself is truly beautiful in certain woods. When you want to have a glistening coat to a horse or dog for example makore is astoundingly good at giving a shimmering effect, Osage orange is superb for fields of corn/wheat Limba is good for hair.

 

[Ttrees]

It can be a nightmare when bookmatching. Most often seen on mass produced guitars and violins etc, I was suggested to me that it is perhaps caused by the direction and sharpness of the tool used to cut or slice the wood. This was suggested to me when I was learning about marquetry and veneering furniture panels by my old master. he pointed out that sequential leaves of veneer would have a similar chatoyence as they were composed of similar enough fibres but that the need to flip over a leaf in order to bookmatch would mean that the fibers were orientated in a different direction or angle in relation to the angle of the cut and therefore reflected light at opposing angles.
I have often thought about an experiment where the direction of cut for each slice of leaf of veneer would be at 180 deg to the previous. IE if first slice is an up-cut then rather than having the veneer slicer continue round for another cut in the same direction it could be reversed and give a downward cut. Obviously you would need a double bladed machine.

Also the fact that on most industrial veneer slicing processes the knives only give a clean "true" cut to one surface. Especially on rotary cut veneer such as for panels, where the underside face of the cut gets badly crushed and cracked compare to the top surface of the veneer.

I've never asked, but seen many luthiers misalign those flame maple backs and other bookmatches on guitar back intentionally, which does seem odd to me.
It could be habits carried over from timbers which would give an invisible joint.
i.e rosewood or the tops.

I don't think the process has anything to do with anything,
as a similar thing regarding the tops of instruments.
Some buy hundreds of sets and only choose the ones with no runout, and sell the rest online.
i.e both leaves appear the same whilst viewed horizontally and not with one
darker than the other leaf.
I can try and dig that snippet out for ya if you like, should it be allowed

 

[profchris]

It can be a nightmare when bookmatching. Most often seen on mass produced guitars and violins etc, I was suggested to me that it is perhaps caused by the direction and sharpness of the tool used to cut or slice the wood. This was suggested to me when I was learning about marquetry and veneering furniture panels by my old master. he pointed out that sequential leaves of veneer would have a similar chatoyence as they were composed of similar enough fibres but that the need to flip over a leaf in order to bookmatch would mean that the fibers were orientated in a different direction or angle in relation to the angle of the cut and therefore reflected light at opposing angles.
I have often thought about an experiment where the direction of cut for each slice of leaf of veneer would be at 180 deg to the previous. IE if first slice is an up-cut then rather than having the veneer slicer continue round for another cut in the same direction it could be reversed and give a downward cut. Obviously you would need a double bladed machine.

Also the fact that on most industrial veneer slicing processes the knives only give a clean "true" cut to one surface. Especially on rotary cut veneer such as for panels, where the underside face of the cut gets badly crushed and cracked compare to the top surface of the veneer.

From the luthiery side, the difference we see when bookmarking is definitely caused by runout. Unless the grain fibres are perfectly parallel to the surface, you see the cut ends of fibres from opposite directions in each half of the bookmatch, which reflect light differently. The surfaces are sawn and planed, so cutting method has no effect.

I'd expect the same in veneers - whether slicing direction changes anything I couldn't say.

 

[chatometry]

No the wood species for a project is imposed beforehand. And one may have a limited supply - if it's not from stock one often buys just enough. My answer has always been to orient the boards available so as to cause the least disturbance. It can be a compromise sometimes in the real world.

Interesting, thanks. I saw a walnut chair where the joint between the vertical and the horizontal pieces showed an impressive mismatch, but in that case you can only try to hide it by finishing.

 

[chatometry]

It can be a nightmare when bookmatching. Most often seen on mass produced guitars and violins etc, I was suggested to me that it is perhaps caused by the direction and sharpness of the tool used to cut or slice the wood. This was suggested to me when I was learning about marquetry and veneering furniture panels by my old master. he pointed out that sequential leaves of veneer would have a similar chatoyence as they were composed of similar enough fibres but that the need to flip over a leaf in order to bookmatch would mean that the fibers were orientated in a different direction or angle in relation to the angle of the cut and therefore reflected light at opposing angles.
I have often thought about an experiment where the direction of cut for each slice of leaf of veneer would be at 180 deg to the previous. IE if first slice is an up-cut then rather than having the veneer slicer continue round for another cut in the same direction it could be reversed and give a downward cut. Obviously you would need a double bladed machine.

Also the fact that on most industrial veneer slicing processes the knives only give a clean "true" cut to one surface. Especially on rotary cut veneer such as for panels, where the underside face of the cut gets badly crushed and cracked compare to the top surface of the veneer.

Thanks for the insight. The effect of veneer slicing is surely not negligible. The sharpness surely makes a difference: within the same wood we found veneers that are more chatoyant before sanding to 1500-grit and some that are more chatoyant after - my interpretation is that is caused by the quality of the veneering process (i.e. sharpness of the tool).
Then it is clear that flipping a veneer along an edge which is not parallel to a fiber creates a mismatch, and this gets worse on figured wood. So I understand that matching two pieces can be a nightmare!
Do you have any pictures of marquetry with Makore or Osage Orange?
Anyway, I would be curious to see the results of the "experiment" you spoke about!

 

[chatometry]

I've never asked, but seen many luthiers misalign those flame maple backs and other bookmatches on guitar back intentionally, which does seem odd to me.
It could be habits carried over from timbers which would give an invisible joint.
i.e rosewood or the tops.

I don't think the process has anything to do with anything,
as a similar thing regarding the tops of instruments.
Some buy hundreds of sets and only choose the ones with no runout, and sell the rest online.
i.e both leaves appear the same whilst viewed horizontally and not with one
darker than the other leaf.
I can try and dig that snippet out for ya if you like, should it be allowed

If you google "violin back" there's a lot of examples... I don't know about guitars. However, matching chatoyance must be hard as @Droogs said...

 

[chatometry]

From the luthiery side, the difference we see when bookmarking is definitely caused by runout. Unless the grain fibres are perfectly parallel to the surface, you see the cut ends of fibres from opposite directions in each half of the bookmatch, which reflect light differently. The surfaces are sawn and planed, so cutting method has no effect.

I'd expect the same in veneers - whether slicing direction changes anything I couldn't say.

Agreed. So is there an active effort to match or intentionally mismatch the effect?

 

[Ttrees]

If you google "violin back" there's a lot of examples... I don't know about guitars. However, matching chatoyance must be hard as @Droogs said...

I'd imagine it's from the violin tradition why this is done, as they are an earlier instrument.
There's no difference in effort to mark the centerline with such thick pieces
to be joined and carved, so must be dare I say for aesthetics....
But much like the way a top with runout will demonstrate?

A question for the luthiers forum I think.

Tom

 

[profchris]

Agreed. So is there an active effort to match or intentionally mismatch the effect?

Ideally all chatoyance from runout would be avoided. This would leave just the chatoyance from other figuring in the grain, so the two halves would look nearly identical.

But to do this, the wood processor has to cleave billets along the grain, and then saw those billets into tops and backs. This means fewer tops and backs from the same billets = more expensive. Thus you see a lot of chatoyancy difference between bookmatch halves in cheaper instruments.

Mismatching in bookmatching is usually because the joined plates are thinned further after joining. The grain pattern changes through the thickness of the piece, so the more that is removed, the greater the divergence. Carved tops and backs, like violin family instruments, carve more away of course.

 

[profchris]

Here's one of my ukuleles. You can see I've got a good bookmatch, but the knot on the left has caused swirly grain on the right, which will diverge more if i thin it further.

And, with finish, the runout becomes apparent, making the lower right part look darker than the lower left, and also changing the appearance of the horizontal figuring lines on each half.

Fortunately all this moves around if you move the instrument, so it looks even more interesting, rather than mismatched.

A high end builder had rejected this wood, so I got to use it. Figured koa is rare, so I wasn't going to waste it!

 

[recipio]

I've noticed it in Sycamore . It has a peculiar sheen which distinguishes it from Maple but you have to look closely.

 

[Ttrees]

@profchris your saying it's to account for the wood,
but I've seen this done on flamed maple with identical figuring also,
likely evident from an easy google folks jointing tops with a step,
lots of folks, and not just a few doing this.

To use your argument about the appearance changing things also,
hasn't as much weight regarding many timbers and why this is done,
if one is to glean anything from why some stagger the joint, on identical examples of species with high chatoyance, the flamed maple being a real good example,
but does get the point across about possible tradition which may well be the reason,
since things weren't as easy back then as going online and buying some identical stock.

I wonder if one googled a "maple back and sides guitar"
and viewed many, I'd guess the majority would be staggered tiger striping....
That is, perfectly staggered and not just by any old amount, with no mismatch regarding the meeting of those stripes, nor width difference to note any variance in the timber.

With some small googling I'm not seeing any staggering of these joints,
so I guess this is done with rosewood or similar invisible joints to denote the centerline, rather than to intentionally get a negative effect .

Whether staggering the joint is a done thing, to possibly achieve a mirror effect
rather than a negative, only on the most consistent examples which this would be possible.
I'd be confident the best answer would be in the realm of the archives on the OLF.


Tom

 

[profchris]

I searched, and all the examples I saw of what looks like a deliberate step bookmatch were on electric guitars, usually Les Paul style carved tops. Maybe it's a fashionable look?

All the acoustics were fairly well mirror imaged. Some don't look it at first sight, but zoom in and you can see that one side is a negative mirror of the other. That's runout, causing opposite chatoyancy on each side - if you could see those in 3D you'd find the mirror match visible at some light angles.