What is the most chatoyant wood?

[chatometry]

Yes, exactly that Paolo...

We also found a lot of variation within the same species, but still some species are always low and some are always high in chatoyance.

Given that there is a lot of discussion about the fact that - in some cases - chatoyance is a nuisance, maybe we should test finishes looking for the best way to kill chatoyance.
I see here that you mentioned "glazes" and "stains" and @Droogs mentioned "industrial chemical finishes".
This could be a test campaign for next year.
Just to make a practical example, the finish on this Iroko floor (internet picture) does not inhibit chatoyance:

One may or may not like the effect, and should finish accordingly - provided data are available as to what finishes work better for the purpose...

 

[Droogs]

For me, although at times a nuisance (in that it makes matching more difficult or restrictive), if I am veneering a couple of doors/drawer fronts etc for a piece and want to have the chatoyance shimmer in the same direction then it can limit me as the maker of the piece as to what joint type I can use to cover the panel. For instance if very highly figured and very chatoyant then I may not be able to mirror bookmatch due to what would be a very marked change in light reflection that would highlight the use of many leaves to cover the panel. For instance a side panel for a sideboard may in direct light show it is made of 4 strips of veneer when the effect i was after was the appearance of one very wide board. So in order to get round this I may use a slip match if I can get a good join that would eliminate the chance of noticing the joins but at the cost of losing the grain pattern effect I may have been looking for over the whole piece or go for a diamond join instead.

On the other hand, when doing pictorial marquetry say a country scene (a repo of Constable's The Hay Wain) I would be looking for pieces of veneer with varying chatoyance from little for the sky, clouds, trees and cottage but high for the water and for the crops in the field to give a feeling of movement of the crop in the wind as you look at the piece and move around it, to medium for the figure and the haywain itself.

It is also very dependent on what finish I would put on such a piece as a dino-juice plastic based finish will give a very different visual look and effect compared to a natural oil or wax finish. I find that modern polymer finishes don't so much as kill or get rid of chatoyance but that they rather overpower it with their own reflectivity before the light hits the wood. Certainly for me when looking at pieces finished in modern "plastics" the reflective effect seems to happen on top of the wood rather than on the surface of the wood

 

[Sgian Dubh]

Given that there is a lot of discussion about the fact that - in some cases - chatoyance is a nuisance, maybe we should test finishes looking for the best way to kill chatoyance.
I see here that you mentioned "glazes" and "stains" and @Droogs mentioned "industrial chemical finishes".
This could be a test campaign for next year.

One may or may not like the effect, and should finish accordingly - provided data are available as to what finishes work better for the purpose...

I'm not sure exactly what your aims are. I'm guessing, erroneously maybe, that you're not approaching the topic as a woodworker nor as a wood finisher, but primarily from the point of view of a researcher, perhaps as a scientist, timber technologist, or even as a wood finishing chemist.

But to undertake research into how you might best kill chatoyance, or how to eliminate or reduce the light/dark effect often seen in frame and panel doors as I outlined in my last post I think my first port of call would be a skilled finisher. Typically, adjusting colour to even up the appearance of rails and stiles involves shading coats. I've done a little of this kind of stuff, but it's not really my forte. As to the parquet floor you included in your last post, I'm not sure you could ever completely eliminate the light/dark thing going on there, but perhaps a properly skilled finisher might be able to point you in the right direction. Incidentally, the light/dark thing in that floor doesn't bother me in the least, and that's because I expect it. Slainte.

 

[Droogs]

I do hope the point of the research is more to be able to class different woods into groups for level of chatoyance rather than for ways to kill or diminish it as this is a big part of the beauty of wood to a woodworker

 

[profchris]

Agreed, chatoyance is a challenge not a nuisance (most of the time).

Here is some nicely chatoyant oak, and this back could look quite dull if it didn't shimmer in different places as you move it.

 

[profchris]

On finishing, I get the deepest looking chatoyance with shellac or nitro lacquer. I'm told traditional oil varnishes are good too. Polyurethane varnish is less good, polyester and water based finishes always look much flatter to me.

A thick finish also diminishes the effect.

 

[chatometry]

For me, although at times a nuisance (in that it makes matching more difficult or restrictive), if I am veneering a couple of doors/drawer fronts etc for a piece and want to have the chatoyance shimmer in the same direction then it can limit me as the maker of the piece as to what joint type I can use to cover the panel. For instance if very highly figured and very chatoyant then I may not be able to mirror bookmatch due to what would be a very marked change in light reflection that would highlight the use of many leaves to cover the panel. For instance a side panel for a sideboard may in direct light show it is made of 4 strips of veneer when the effect i was after was the appearance of one very wide board. So in order to get round this I may use a slip match if I can get a good join that would eliminate the chance of noticing the joins but at the cost of losing the grain pattern effect I may have been looking for over the whole piece or go for a diamond join instead.

On the other hand, when doing pictorial marquetry say a country scene (a repo of Constable's The Hay Wain) I would be looking for pieces of veneer with varying chatoyance from little for the sky, clouds, trees and cottage but high for the water and for the crops in the field to give a feeling of movement of the crop in the wind as you look at the piece and move around it, to medium for the figure and the haywain itself.

It is also very dependent on what finish I would put on such a piece as a dino-juice plastic based finish will give a very different visual look and effect compared to a natural oil or wax finish. I find that modern polymer finishes don't so much as kill or get rid of chatoyance but that they rather overpower it with their own reflectivity before the light hits the wood. Certainly for me when looking at pieces finished in modern "plastics" the reflective effect seems to happen on top of the wood rather than on the surface of the wood

Thanks again for the very interesting insight. I understand that your work is mainly on furniture an marquetry, am I right?

 

[chatometry]

I'm not sure exactly what your aims are. I'm guessing, erroneously maybe, that you're not approaching the topic as a woodworker nor as a wood finisher, but primarily from the point of view of a researcher, perhaps as a scientist, timber technologist, or even as a wood finishing chemist.

But to undertake research into how you might best kill chatoyance, or how to eliminate or reduce the light/dark effect often seen in frame and panel doors as I outlined in my last post I think my first port of call would be a skilled finisher. Typically, adjusting colour to even up the appearance of rails and stiles involves shading coats. I've done a little of this kind of stuff, but it's not really my forte. As to the parquet floor you included in your last post, I'm not sure you could ever completely eliminate the light/dark thing going on there, but perhaps a properly skilled finisher might be able to point you in the right direction. Incidentally, the light/dark thing in that floor doesn't bother me in the least, and that's because I expect it. Slainte.

Thanks. This sounds like a good suggestion.
We are approaching the subject as researchers, but in my previous life I did some woodworking and I really loved when I saw chatoyance...
So, in reply to @Droogs, our research is mainly aimed at characterizing common wood species in terms of chatoyance. We found a whole range of results, from Ziricote, averaging PZC 7.0 to Koa, averaging PZC 26.4.
Now finding samples from new species is getting difficult so we are also making a number of finishing tests which - until now - were aimed at understanding how to maximise chatoyance.

@profchris thanks for the nice oak picture and for the finishing suggestions. Would you bet on shellac for ALL species, or would you discard it on some? (after hearing your answer I will explain my question...)

 

[profchris]

I could use shellac on all species. Those with large pores need some filling to get the full effect though.

As a researcher in another field, can I stress that you need comparability between species, which means finding a consistent cut and average grain pattern. The oak I showed has much more figure than most, and isn't typical. In any species, the degree of runout changes the chatoyance. So you need to control for both these factors.

 

[chatometry]

I was asking because we tested a bunch of different finishes on some wood species, and both shellac and boiled linseed oil appeared to be better than nitrocellulose lacquer on Maple, but worse on Ash.
This was a bit of a surprise to me, and I'd be happy to understand why...

Speaking about runout, you make a very good point, to which we cannot provide a complete answer because we never tested chatoyance vs runout. In addition at the moment I do not have access to our full results database. However: imagine how the test is carried out, that is:
- a light pointed at the sample surface with 60° incidence angle
- the light can rotate around an axis which is normal to the sample surface, passing through the sample center
- the camera optical axis is ~ coincident with the light rotation axis
- the light angular position is defined by theta, with value zero when the light is roughly perpendicular to the fiber direction

Under these conditions, you normally get this brightness vs theta chart:

This shape was found on thousands of samples from more than 100 species, many of which had some runout.
Anyway, when there is A LOT of runout, you get something like this:

we only found this on a handful of samples; this can be seen on this Koa sample:

This is also explained by Savva, here, figure 3.2 onwards:
https://ecommons.cornell.edu/bitstr...ornell_0058O_10056.pdf?sequence=1&isAllowed=y
I believe that a small runout does not give a significant impact on chatoyance, however I will dig out more data next month.

Runout is one of an endless list of parameters that affect chatoyance...

Paolo

 

[Droogs]

In the Koa example above, the left hand 1/3 gives the effect of chatoyance I would be looking for in a piece being used for the hind 1/4s of a horse and would be orientated at a different angle to the piece next to it being used for the chest/back of the horse so that the chatoyance would give a feeling of living 3d depth to an image. It gives the impresion of living movable muscle under the coat and helps the viewers minds eye to give a more rounded feel to the flat surface. The effect being a lot less cartoon/drawing feel to an image and more like a photo realistic painting

 

[chatometry]

I wish I could see some of your work and make a gif out of it, because photos do not make justice to wood

 

[chatometry]

This Koa panel I saw on a website reminded me of this discussion...

 

[TRITON]

For me it has to be Waterfall Bubinga.

I wonder how the structure of the tree forms such an amazing figuring.

 

[chatometry]

Bubinga is fairly high (average PZC =19.2) in our measurements.
Some examples here:
https://www.chatometry.com/home-page/bubinga/(all pictures show sample sanded to 1500-grit and no finish)
I would assume that the waterfall is due to fibers taking the shape of a woman's curly hair...

 

[raffo]

Bubinga is fairly high (average PZC =19.2) in our measurements.
Some examples here:
https://www.chatometry.com/home-page/bubinga/(all pictures show sample sanded to 1500-grit and no finish)

Just to add to the variables, it would be interesting to hand plane your samples with a bevel down smoother plane properly set up. The surface left by such a plane is mirror like in some cases since the fibers will be cleanly cut. There will not be a need to sand it.

Also, to answer your question about the use of a burnisher, the device crushes the fibers.

 

[D_W]

Khaya has some of the greatest depth, but I'd find something like paramaterizing this with independent variables pretty confusing.

When I get new guitar blanks, sometimes I use them to experiment before cutting the blank out and starting anew. The experimentation is usually trying to speed things up - in this case, french polish, trying to fill the pores during the process with something faster than pumice and definitely faster than working with bare shellac.

But this piece has great depth, and the next guitar blank from it may look flat with almost nothing. The depth is due to ribboning.

there's another characteristic of something like spruce where there is detail between the grains if the surface is done cleanly, but it's on a small scale and harder to notice. Is it chatoyance? I don't know.

I think this body blank in the video is a little bit garish, but the effect in person is far greater than it is in the picture here, too. It's garish because the ribboning isn't neat and even. And even were it to be more perfect, it could still be too strong and make a guitar look odd.

As far as small runout, I think that's generally what ribboning and curl are, and wood with the effect you're showing a few posts prior is pretty common in crotch blanks or something similar.

 

[chatometry]

Just to add to the variables, it would be interesting to hand plane your samples with a bevel down smoother plane properly set up. The surface left by such a plane is mirror like in some cases since the fibers will be cleanly cut. There will not be a need to sand it.

Also, to answer your question about the use of a burnisher, the device crushes the fibers.

This test is in our to-do list. The only issue is that planing is an art in itself, and I definitely do not master it.
Would you be up for supplying a planed sample, whose chatoyance we will measure "as received" and then after sanding to various grits?
Just 1.75*5*1/2" is enough, and it should be some chatoyant wood (walnut, maple, sapele, bubinga, the list is very long).
I would expect that chatoyance after planing is similar to chatoyance after some very high grit sanding.

 

[chatometry]

Khaya has some of the greatest depth, but I'd find something like paramaterizing this with independent variables pretty confusing.

Awesome piece. So far Khaya is n.5 out of 105 species we tested, so very high indeed (PZC 21.5)

When I get new guitar blanks, sometimes I use them to experiment before cutting the blank out and starting anew. The experimentation is usually trying to speed things up - in this case, french polish, trying to fill the pores during the process with something faster than pumice and definitely faster than working with bare shellac.

Interesting. Did you notice differences between species, i.e. each wood prefers a different finish?
We are running many tests on this, you can find them on our website (www.chatometry.com) under the case studies -> finishing section.

But this piece has great depth, and the next guitar blank from it may look flat with almost nothing. The depth is due to ribboning.

Yes, figure highlights the property; also flecks do it.

there's another characteristic of something like spruce where there is detail between the grains if the surface is done cleanly, but it's on a small scale and harder to notice. Is it chatoyance? I don't know.

I don't know. It seems like early growth in softwoods is another matter.

I think this body blank in the video is a little bit garish, but the effect in person is far greater than it is in the picture here, too. It's garish because the ribboning isn't neat and even. And even were it to be more perfect, it could still be too strong and make a guitar look odd.

I believe that the "depth" is very evident in person for this reason: you have two eyes, and they see the wood piece from a different angle; in a chatoyant wood, this difference in the angle turns into a perceivable colour difference which the brain sees as depth. At least, this is my thought.

Does a 1.75*5*1/2" rectangle fit within your typical cutoffs?

Paolo

 

[D_W]

Does a 1.75*5*1/2" rectangle fit within your typical cutoffs?

Paolo

Often it will, depending on direction. this blank is pretty large and should have much to spare. these are pre-sawn and sold here so the larger ones often labeled for larger guitars, but then sold for the same or similar price as smaller, so I usually just have more wood to discard.

I haven't had a chance to note much difference on wood finish preference as I generally only use two finishes - shellac french polish or waterborne sprayed over shellac as a sealer and toner. Gloss definitely does something for this, but I am experimenting in this piece and unsure if sanding the finish in has affected anything given it can produce poor results with a french polish if some of the material filling pores remains on the wood and isn't completely removed.

I'm more curious re: what raffo mentioned - what change sanding vs. planing would have, but think that with french polish, I could not tell without doing a dozen test pieces on the same blank. The difference in finish absorption is pretty large on a planed vs. sanded finish in that shellac will build almost from the first coat on a planed surface, but sanded will absorb quite a bit - this is far different vs. what you're testing, though.