Yes, many show chatoyance. Down side is I don't have time to get into them to share photos for a while, maybe November....
Most chatoyant wood species?
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Thanks
This tells us that at least some species retain some chatoyance after a century of aging (and oxygen exposure, as I guess they were not airtight packaged).
This tells us that at least some species retain some chatoyance after a century of aging (and oxygen exposure, as I guess they were not airtight packaged).
True Paul, you are correct, I do not totally agree with your #50 post.
I am immensely aware that even a very finely sanded and polished wood surface is not a proverbial flat plane. Years ago, I was bothered by two things - the statement that sanding clogs the wood pores, and the way that wood stain acts - well, they also tied into myths within the bbq world. If you took culms of bamboo, rive them into equal halves longitudinally, turn them split sides out and hot glue them to something flat, you would end up with something resembling the surface of seasoned wood. That was an epiphany for Lil Mikey. Yet, it did not by itself explain lots of my questions at the time - but keep that vision in mind. Just postulations. Ok, tie that idea of the wood surface into a common tablespoon. Take a common shiny table spoon. View the back of the spoon - the convex part and what do you see? I see Lil Mikey's ugly face reflected back at me. Now turn the spoon around and view the concave side. Now I see Lil Mikey's face, but upside down and opposite handed. And since the bowl of a spoon is not part of a perfect sphere, the reflection is somewhat distorted making Lil Mikey more uglier. There has to be some magic involved since if you could hold the spoon close enough to your face the face would be right side up, but turn upside down as it moves out. Has to do with angles of reflectance and where that and the rays along the axis intersect. So then Lil Mikey wondered what would happen if instead of a sphere there was a shiny tube. The reflection on the outside of the tube is right side up no matter which direction the tube is positioned. But when Lil Mikey wanted to see what the inner concave surface of the tube would do - he was stymied - there ain't a lot of shiny half tubes around - so he dropped his inquiry until one day much later. One day he was sitting on th.......errr....the throne, when he happened to note that the toilet paper holder was shiny and the part that was recessed into the wall was tubular and concave. Eureka! So this being a construction company, we always have leftovers and knew I had noticed some out in the warehouse. So finished my duty and went to the warehouse to find out that the day before the leftovers had been given to Habitiat. So Lil Mikey went back into the little room, shut AND locked the door - didn't want anyone to think he was strange in any way. He sat on the floor, removed the toilet paper and looked at his reflection in the toilet paper holder body. If his face was perpendicular with the axis of the tube, then his face was upside down, but correct handed. Along the axis of the tube everything was "normal", but perpendicular it was upside down. Now all that could probably have been discovered with ray diagrams, but it was certainly more fun to sit on the floor of a bathroom to make the discovery! BTW the restroom has a faucet with a shiny chrome concave shape where at about a foot from it, the reflection turns upside down! For those who want to know - it doesn't take much to fascinate Lil Mikey1
So that is the reason for all the questions about light travels, angles of reflection and such. What they have recorded is a constant axis, and a constant angle between the light and the axis. The light does however, travel at differing angles from the longitudinal axis of the piece of wood. They found that brightness peaks when it is perpendicular to the fiber axis. That would make sense (I think) if the light is reflecting off of a concave tubular surface. If from a sperical surface as the light traverses it's course, all angle would be the same relative to the axis and should not change. Same with a perfectly flat surface.
"If you look at the surface of the Earth from far enough away it appears flat, but when you get up close enough you see that it has peaks and valleys." That is a partial explanation. True, our eyes are not capable of resolving detail from 100,000's or 1,000,000's miles away. It would be like comparing the resolution power of a 2mp camera image on a very low resolution monitor to the beautiful tonality and detail of an Ansel Adams contact film print taken with his 8x10 Deardorf. The earth is 1 AU from the sun or 93,000,000 miles (avg of the aphelion and the perihelion). Even though the sun is immense in comparison to the earth - at 93,000,000 miles it acts as a focused point of light with very little spread. So viewing the earth from miles and miles away with the sun at our back, there would be little if not any discernible shadows - therefore - little contrast to discern shapes by. Kinda like the proverbial overhead photo of camels on a sand dune lit by either a setting or rising sun. Shadows are thrown that allow you to ascertain the shape. If it was shot with the sun directly overhead (90 deg to surface) and the camera also at 90 deg to the surface all you would see would be the exterior outline of the camel from above and might not know it is a camel.
"Sanding gets rid of at least the biggest variations in the peaks and valleys in the wood which is why well sanded wood will show chatoyancy that rough wood won't." This is why my question of whether the reflectance is from the cut edge of the dead cell walls or from the concave inner surface of the cut open cell wall. In reality there could be a certain number of uncut dead cell walls (convex surfaces). The smaller the cell, possibly the greater number of uncut cells and more reflectance. If the brightest reflectance is due to fiber orientation, it should not make a difference that there is hills and valleys. Yes it does make a difference to bent wood fibers such as curl and quilt. I would suspect that sanding is and its effect on chatoyance is more mechanical. As cut the edges of the dead cell walls are pretty ragged and may cause at least part of the light exiting the empty cell to be diffused or specularized. By sanding those fuzzy cell edges are smoothed out and might not diffuse the light as much. It would be nice to have a scanning electron microscope in the back bedroom to use to answer just such a question. I would assume the way to know this is to observe how the light reacts when perpendicular to the fiber axis. But my brain isn't big enough to know the answer. Or is the light acting like a gem. Faceting of a gem has a lot to do with how much sparkle (reflection) and the color of the sparkle (refraction) it has. A facet is a cut and polished small flat face of a gem. There may be thousands on a certain gem cut pattern - each cut to a high degree of accuracy and precision. A ray of light passes through a facet and is reflected off the facets on the opposite side of the gem. If those facets are somehow aligned such that the light ray eventually pass back out that facet - then the facet sparkles. If the facets are somehow aligned such that the light bounces around and exits the gem through other facets then that facet is dark. I wonder if the inner walls of the cell act in that way? And yes, I have a faceting machine!
I am immensely aware that even a very finely sanded and polished wood surface is not a proverbial flat plane. Years ago, I was bothered by two things - the statement that sanding clogs the wood pores, and the way that wood stain acts - well, they also tied into myths within the bbq world. If you took culms of bamboo, rive them into equal halves longitudinally, turn them split sides out and hot glue them to something flat, you would end up with something resembling the surface of seasoned wood. That was an epiphany for Lil Mikey. Yet, it did not by itself explain lots of my questions at the time - but keep that vision in mind. Just postulations. Ok, tie that idea of the wood surface into a common tablespoon. Take a common shiny table spoon. View the back of the spoon - the convex part and what do you see? I see Lil Mikey's ugly face reflected back at me. Now turn the spoon around and view the concave side. Now I see Lil Mikey's face, but upside down and opposite handed. And since the bowl of a spoon is not part of a perfect sphere, the reflection is somewhat distorted making Lil Mikey more uglier. There has to be some magic involved since if you could hold the spoon close enough to your face the face would be right side up, but turn upside down as it moves out. Has to do with angles of reflectance and where that and the rays along the axis intersect. So then Lil Mikey wondered what would happen if instead of a sphere there was a shiny tube. The reflection on the outside of the tube is right side up no matter which direction the tube is positioned. But when Lil Mikey wanted to see what the inner concave surface of the tube would do - he was stymied - there ain't a lot of shiny half tubes around - so he dropped his inquiry until one day much later. One day he was sitting on th.......errr....the throne, when he happened to note that the toilet paper holder was shiny and the part that was recessed into the wall was tubular and concave. Eureka! So this being a construction company, we always have leftovers and knew I had noticed some out in the warehouse. So finished my duty and went to the warehouse to find out that the day before the leftovers had been given to Habitiat. So Lil Mikey went back into the little room, shut AND locked the door - didn't want anyone to think he was strange in any way. He sat on the floor, removed the toilet paper and looked at his reflection in the toilet paper holder body. If his face was perpendicular with the axis of the tube, then his face was upside down, but correct handed. Along the axis of the tube everything was "normal", but perpendicular it was upside down. Now all that could probably have been discovered with ray diagrams, but it was certainly more fun to sit on the floor of a bathroom to make the discovery! BTW the restroom has a faucet with a shiny chrome concave shape where at about a foot from it, the reflection turns upside down! For those who want to know - it doesn't take much to fascinate Lil Mikey1
So that is the reason for all the questions about light travels, angles of reflection and such. What they have recorded is a constant axis, and a constant angle between the light and the axis. The light does however, travel at differing angles from the longitudinal axis of the piece of wood. They found that brightness peaks when it is perpendicular to the fiber axis. That would make sense (I think) if the light is reflecting off of a concave tubular surface. If from a sperical surface as the light traverses it's course, all angle would be the same relative to the axis and should not change. Same with a perfectly flat surface.
"If you look at the surface of the Earth from far enough away it appears flat, but when you get up close enough you see that it has peaks and valleys." That is a partial explanation. True, our eyes are not capable of resolving detail from 100,000's or 1,000,000's miles away. It would be like comparing the resolution power of a 2mp camera image on a very low resolution monitor to the beautiful tonality and detail of an Ansel Adams contact film print taken with his 8x10 Deardorf. The earth is 1 AU from the sun or 93,000,000 miles (avg of the aphelion and the perihelion). Even though the sun is immense in comparison to the earth - at 93,000,000 miles it acts as a focused point of light with very little spread. So viewing the earth from miles and miles away with the sun at our back, there would be little if not any discernible shadows - therefore - little contrast to discern shapes by. Kinda like the proverbial overhead photo of camels on a sand dune lit by either a setting or rising sun. Shadows are thrown that allow you to ascertain the shape. If it was shot with the sun directly overhead (90 deg to surface) and the camera also at 90 deg to the surface all you would see would be the exterior outline of the camel from above and might not know it is a camel.
"Sanding gets rid of at least the biggest variations in the peaks and valleys in the wood which is why well sanded wood will show chatoyancy that rough wood won't." This is why my question of whether the reflectance is from the cut edge of the dead cell walls or from the concave inner surface of the cut open cell wall. In reality there could be a certain number of uncut dead cell walls (convex surfaces). The smaller the cell, possibly the greater number of uncut cells and more reflectance. If the brightest reflectance is due to fiber orientation, it should not make a difference that there is hills and valleys. Yes it does make a difference to bent wood fibers such as curl and quilt. I would suspect that sanding is and its effect on chatoyance is more mechanical. As cut the edges of the dead cell walls are pretty ragged and may cause at least part of the light exiting the empty cell to be diffused or specularized. By sanding those fuzzy cell edges are smoothed out and might not diffuse the light as much. It would be nice to have a scanning electron microscope in the back bedroom to use to answer just such a question. I would assume the way to know this is to observe how the light reacts when perpendicular to the fiber axis. But my brain isn't big enough to know the answer. Or is the light acting like a gem. Faceting of a gem has a lot to do with how much sparkle (reflection) and the color of the sparkle (refraction) it has. A facet is a cut and polished small flat face of a gem. There may be thousands on a certain gem cut pattern - each cut to a high degree of accuracy and precision. A ray of light passes through a facet and is reflected off the facets on the opposite side of the gem. If those facets are somehow aligned such that the light ray eventually pass back out that facet - then the facet sparkles. If the facets are somehow aligned such that the light bounces around and exits the gem through other facets then that facet is dark. I wonder if the inner walls of the cell act in that way? And yes, I have a faceting machine!
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- Thread Starter Thread Starter
- #84
@Mike Hill
This article explains some of the points we've been discussing about:
digital-library.theiet.org
In general, chatoyance has been modeled for computer graphics purposes, so the effect is generally well known in qualitative terms: this article shows something:
arxiv.org
(@phinds the fiber distortion we've been discussing is shown at page 16)
The reason behind chatoyance may be more complex than we know. One example is human hair (yes, they are chatoyant). This article shows that this is related to the "scaled" microgeometry of hair:
www.researchgate.net
This article explains some of the points we've been discussing about:
IET Digital Library: Estimating fibre orientation in spruce using lighting direction
Softwood is almost entirely composed of fibres and its physical properties depend on their orientation. A method is proposed to estimate the average fibre orientation at each pixel in the inspection image. In this study it is shown that finished wood has distinctive reflectance properties that...
digital-library.theiet.org
In general, chatoyance has been modeled for computer graphics purposes, so the effect is generally well known in qualitative terms: this article shows something:
Procedural wood textures
Existing bidirectional reflectance distribution function (BRDF) models are capable of capturing the distinctive highlights produced by the fibrous nature of wood. However, capturing parameter textures for even a single specimen remains a laborious process requiring specialized equipment. In this...
arxiv.org
(@phinds the fiber distortion we've been discussing is shown at page 16)
The reason behind chatoyance may be more complex than we know. One example is human hair (yes, they are chatoyant). This article shows that this is related to the "scaled" microgeometry of hair:
(PDF) Light scattering from human hair fibers
PDF | Light scattering from hair is normally simulated in computer graphics using Kajiya and Kay's classic phenomenological model. We have made new... | Find, read and cite all the research you need on ResearchGate
www.researchgate.net
- Thread Starter Thread Starter
- #85
You were right. The piece I showed was not quartercut:
We have two samples which show the kind of figure you mentioned, and some localizeed areas have some chatoyance, which is well highlighted by adjacent non-chatoyant areas.
These are quartersawn:
From the numerical point of view the results are very low (<7) on these samples too, but this is because we are averaging over a large area most of which is non-chatoyant. We will need to localize the measurement on a specific spot to see what comes out.
Thanks for highlighting this property of QS Ziricote.
Paolo thank you for checking on that and for verification. All ziricote are typically slab sawn cut. True quarter sawn ziricote is very hard to find.
Even your 2 samples shown aren’t true quarter sawn cut. You can can see how the growth rings how it deviates greatly in flat sawn direction even when you have 3-4 winter rings are close to being perpendicular. True quarter sawn ziricote will be filled with ray flakes up and down the board and will be 90 degrees. Those by my experience- visually to me anyways will have higher chatoyance factor.
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Arn is, as usual, correct. I have had a LOT of zircote samples and not a one was true quartersawn. I think about 6 or 8 degrees off was the best I saw. BUT ... I once ran across an almost perfectly quartersawn plank in an exotic wood store.
@phinds this is a great example- this is what I am talking about and that is as close you will get for a well quartered piece. You can even see all the ray flakes on the sapwood and notice there is no spiral grain pattern or cascading curve pattern. A clear horizontal band pattern will tend to be true quarter sawn with the added ray flakes for ziricote. That is an ideal sample for Paulo to measure.
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- Thread Starter Thread Starter
- #89
I will see if I can find something like that here.
With reference to the first gif I posted in message #85, this is the chatoyance map [white means chatoyance, black means no chatoyance]. I see black spots (flakes) of no chatoyance on a more chatoyant background, with the black spots covering a significant fraction of the surface.
We saw a similar behavior in other cases, such as this map from a Field Maple sample:
@Arn213 What is your experience with Bocote? We found it quite non-chatoyant, except for this sample which reaches almost 14 on the scale:
[Bocote sanded to 1500-grit]
With reference to the first gif I posted in message #85, this is the chatoyance map [white means chatoyance, black means no chatoyance]. I see black spots (flakes) of no chatoyance on a more chatoyant background, with the black spots covering a significant fraction of the surface.
We saw a similar behavior in other cases, such as this map from a Field Maple sample:
@Arn213 What is your experience with Bocote? We found it quite non-chatoyant, except for this sample which reaches almost 14 on the scale:
[Bocote sanded to 1500-grit]
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I have not found bocote to be chatoyant in general but the occasional quartersawn piece will show a fair amount. Like this area of a mostly quartersawn plank
That makes absolutely no sense to me. On a static picture there is NO chatoyancy. If you take oak, for example, the light/dark areas change places as you move the piece so BOTH areas have chatoyancy but only when the piece is moving.
Like this:
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- Thread Starter Thread Starter
- #92
Why "static picture"? The grayscale pictures I am showing are maps showing where chatoyance is high and low, not wood pictures. For wood pictures I am showing animated gifs.
True for some species, like this European Beech sample (1500-grit):
Both areas have similar chatoyance.
(I don't have a good quartersawn oak example available, but I agree with you that in oak both areas are quite chatoyant. I also noticed it on bog oak)
Some other species show significant difference between the areas, like this London Plane sample (1500-grit):
We have preliminary data on Louro Faia which also shows much lower chatoyance on Flecks.
Does it make sense?
And my point is that as far as I can tell, in the oak in the link I provided as an example, the amount of chatoyancy does not vary significantly from the flakes to the non-flake areas, so a static picture showing chatoyancy would be all white which would not be helpful. What am I missing?
WAIT ... you show what I'm talking about yourself in your London plane example. It has fairly high chatoyancy in the non-flake areas AND the flake areas and yet your static pic shows no (or little) chatoyancy in the flakes.
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I am surprise it is even that high for bocote with what looks like an off quarter cut. Same experience as Paul and he is correct that you have to have a true quarter sawn piece with the ray flakes showing to get more chatoyant out of it (per his photo sample), but in general I don’t find it chatoyant at all.
It would also help establish a perimeter if you delineate the test based on flat sawn versus true quarter sawn as it will effect your readings. The other condition is to show non figured versus non figured wood readings from the same species.
If you focus on the flake area, it never truly flashes like the other parts. True, the color changes but not intensely
The color changes TOTALLY from light to dark and back again. I believe that that is the DEFINTION of chatoyancy --- something that changes color or shininess depending on the angle at which you view it.
I agree it appears to change. I also agree about the definition of chatoyance. They arent exactly measuring what we define as chatoyance but rather the changing reflectivity of the surfaces and the amount of reflection coupled with the change in the amount of reflection is going into these computations.
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- #98
Exactly...but it would tell you that every part is chatoyant, which is an information.
True. These maps show an intermediate parameter (not the PZC). We plan to re-plot them with the PZC, but it will take some time.
However, what @2feathers Creative Making says us true: the flecks do not change their brightness as intensely as the other areas. In general this makes sense: these are different cells cut in a different way, so one could expect a difference - at least, that's my thought.
This is an important point. Let me explain my thought as it is now.
Most softwoods show higher chatoyance on latewood. So if you take a QS or RS section you cross a number of growth rings and you correctly average latewood and earlywood chatoyance. But if you take a FS section (of a very large tree) you may end up with a measurement area that is all on latewood or on all earlywood, and this can give significantly altered results. This Douglas Fir example shows the idea:
So on softwood I am happy with any cut, as long as my measurement includes at least one complete growth ring.
On hardwood we have flecks, which could make a perfect QS cut significantly different from any other cut (as you taught me). In fact flecks also appear in other cuts, but under a completely different look: they cover a lower area and they (possibly) show a different chatoyance.
So let's design together a test to clarify this point; my proposal is:
Find a wood blank at least 12*1.75*1.75 that is perfectly QS on one side.
The wood should be something fairly chatoyant with evident flecks. Maybe London Plane?
Cut the first 6" and slice it to make QS samples, and the other 6" to make FS samples.
Otherwise I can check if I already have some Sessile Oak (that's the everyday hardwood here).
I can get access to loads of Field Maple, but flecks are not always evident on that - am I right?
Paolo
I may have an American sycamore plank that has an area of strong flakes and an area of no, or very small, flakes. I'll look later today.
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- #100
Don't worry, I will look for something locally.
Any other ideas in addition to sycamore/plane and oak?
Any other ideas in addition to sycamore/plane and oak?