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Chatoyance


Janel

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I am drawn to certain pieces of wood because of the bright ripple of the grain. Light is reflected differently, and often makes me think of the surface of water. How about any of you?

 

What is Chatoyance? Why does wood have it or not have it, what causes the wood to grow that way?

 

How does anyone use it to enhance the piece being carved?

 

What do you do to enhance the Chatoyance?

 

What woods have you found with Chatoyance?

 

Does it is more or less difficult to work with?

 

How would one enhance it with finish treatments? Does it stain well, or not?

 

Do any other materials besides wood have Chatoyance? Minerals do, that is part of the dictionary definition. What else?

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Interesting subject, Janel. I like chatoyant woods and other materials, and use some frequently. I don't have all the answers, but I'll tell you what I do know.

 

Chatoyance as I understand it is the appearance of shifting patterns in something. For instance, curly maple is a common chatoyant wood. When finished you can change its position relative to the light source and see the darker and lighter curls running across the grain change places. I have been told that the curls in wood are formed because the wind blows in the same direction most of the time for many years and sets up a type of stress in the tree. I suspect stresses, whether curls or other patterns, come from some something that causes the wood fibers to turn or compress in different directions, causing light to reflect differently at different angles.

 

Chatoyance is enhanced by the way the material if finished. Blond woods like curly maple can be stained to give better contrast to the chatoyant curls and the normal grain. (I've found that using a spirit bases stain works better than an oil based stain. It is thinner and penetrates deeper.) Dark woods like curly koa or curly clero walnut aren't usually stained. I usually give wood a tung oil finish of many layers. This "wetting" really enhances the chatoyant characteristics. To see the grain of a raw piece of wood you can wet it (some of us just spit on it, but water or alcohol are fine). I've also seen wood that has been stabilized using the modern process of infusing acrylics at the cellular level enhance the chatoyant effect. Not all chatoyand woods will take a finish. For ironwood I sand above 600 grit, then lightly buff it with a fine white alumina compound.

 

Most of the curly woods I've seen are chatoyant. Maple is very common, as is koa and clero walnut, but I've seen curls in many woods like oak, pecan, and several of the African and Australian woods. I've been told it can occur in any species of wood if the conditions are right.

 

I've seen curly maple that is sawn and planed, and it's rough with raised curls. I don't really do conventional wood work, as my knife handles are ground to shape and sanded, so I don't have that problem. Any I've tried do sand smoothly. If you are cutting the wood with chisels it you may notice harder and softer spots.

 

I have experienced chatoyance in many of the damascus steels I've used for knives. It will depend upon the pattern and how it was made, plus the number of layers. A fine layered ladder pattern will have it's layers turned on end so to speak and parts are very close together. After it is etched (I etch deeply) and top layers polish by hand or lightly buffed, you can get the light shifting around the blade just like on curly maple. Any pattern where the layers are turned "out" and exposed and done at a higher layer count can do this. I had no idea this would happen until one of my early damascus knive showed it. After etching it I used a thick piece of leather and Semi-Chrome polish to work the surface. I got pretty excited when I started seeing the rippling!

 

Hope this helps.

 

David

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Aloha Janel,

 

You've touched on a subject dear to my heart (and my pocketbook). Koa is probably Hawaii's most known, used and traded wood. Ask David B. As such, it has become a hot commodity. Prices range from US$20/BF (1"X12"X12") for common to $45-75+ for higher grades. What makes this wood so desirable? Curl (chatoyance). The folks at Woodweb have covered it pretty well. Controversy rages here (driven by $ and the highly subjective grading system) along the lines of your questions.

The effect of chatoyance is the reflection of light by an object. My personal opinion, for woods here, is that it is a combination of genetics, growth patterns, environment and mineral uptake by the tree's xylem.

Genetics - there is a small grove at an "undisclosed location" where every tree has curl from branch to root. There is no other population I know of that displays this effect. We call them "the Mother of Curl".

Growth patterns - trees subjected to wind deflection seem to show curl in the crooks and bends, where they submit to nature. We call this compression curl. It's characteristics are curl in X, Y and Z axis (flat and quarter sawn simultaneously) and a noticable telegraphing of the effect on the exterior of the tree through the bark.

Environment - koa grows form sea level to high altitude. Being from the nitrogen fixing Family, Leguminosae, it can grow fast. At lower altitudes, the wood is softer and growth rings are wide. Not the best curl. At higher altitudes, harder woods and tight rings. That gives you characteristics such as brighter chatoyance, better response to chatoyance enhancing finishes and the ability to impart finer detail.

Mineral uptake - the islands form an arc from Kauai to Hawaii (the Big Isle). All volcanic in nature, they differ in age by millions of years. Erosion and leaching leaves the soils on older islands poor in minerals. Newer, volcanically active islands are where the koa hunters go. You can see the difference dramatically. I think it's the silicates, among other minerals. They weather out fairly quickly. Additionally, they abrade tooling aggressively. You don't see this on Kauai koa. It affects color also. "Fresher" soils produces the palette of black, brown, yellow, red and orange. Older soils do not.

I have focused on curl, but chatoyance can also be overall "glow" to the wood. I've found problems with working characteristics minimal, except for curl. Splits can occur along grain lines, especially with compression curl. (I dry my stock according to traditional Japanese guidelines; air drying at least 5 years and cutting a longitudinal slit to relieve tension.) With changes in grain direction, you have to stay on your toes. Scraping is most effective, so the harder the better.

Most clear, oil-based finishes and transparent dyes enhance chatoyance. Water-based, acrylics and pigment-based stains do not.

Hawaii is blessed (with regards to woods) in many ways. We have endemic trees which (by definition) are found nowhere else. Waves of immigrants have brought seeds and cuttings from all over the world. (Look at persimmon or kaki wood.) A Territorial Forester named Hosmer went on a planting rampage in the 1920's and seeded exotic stock everywhere. Those trees are now maturing. Now add in high altitudes (to 13,000 ft.), high winds to spread the stock and form compression curl and volcanic soil. :blink:

I may be wrong, but would you call what you see in marine shells and insect bodies, chatoyance?

Anyway, I've gone on a bit and Maui is calling. It's a dangerous job, but somebody has to do it. :rolleyes:

 

KC

 

p.s. - I'm doing a little research on ebonization and a few other techniques.

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Hallo David,

 

although I am not really a woodie I find this subject fascinating. :rolleyes:

 

Do you think it could be possible to gain suchlike effect with mokume or do this need a very large number of layers? (The number of layers in mokume is somewhat limited because the metals tend to alloy completely whem becoming too thin)

 

regards,

Karl

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Many woods will exhibit a flash or rolling shimmer depending on the orientation of cut . maple,basswood,walnut,birch are a few of the local woods.

 

Stains can enhance the figure in wood and each piece will do something different in regards of the color and type of stain.

 

 

Minnesota Basswood

basswood004a.jpg

 

 

Quilted Maple

Daves002a.jpg

 

 

Birch

bbclone4.jpg

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Great information David, thanks!

 

"I've found that using a spirit bases stain works better than an oil based stain. It is thinner and penetrates deeper."

 

Question 1- Must you be fastidious about working the surface to remove all scratches before using a darkening stain? I really dislike surprises, work at great length to remove scratches on the hardest woods, but maple, for instance, is softer than what I normally use.

 

Question 2- Would thinning artist oil paint with mineral spirits or turpentine be equivalent to using spirit based stains?

 

"some of us just spit on it" - I thought I was alone with this! Mom taught us to spit on rocks while she was raising her little pack of rock hounds :rolleyes:

 

"curly maple that is sawn and planed, and it's rough with raised curls" This is a good bit of information to consider. I really like the looks of curly maple, but fear committing a piece to it if there is much carving, so if some carving is done with a rotary tool, maybe there might be fewer complications with the grain and smoothness? Something to try, at any rate.

 

"I usually give wood a tung oil finish of many layers" How many layers? I have not been happy with its use, but maybe I am not using it right, or have not been patient enough to build up many layers... I also want a surface that won't be affected by moisture from sweaty hands, or worse.

 

The damascus steel chatoyance must be wonderful to experience! Is this something that you can repeat with enough layers and and layer movement?

 

Chatoyance is difficult to capture and show in photos, but it would be great if the members might give it a try with posting images of it in our work. I'll start and give it a try:

 

379_8847.jpg

 

379_4w.jpg

 

379_1w.jpg

 

http://janeljacobson.com/carvings/379.html for a few more details about the piece.

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Hey! Great responses!

 

Yes Karl, I think that Mother-of-Pearl and other shells that glimmer and glow in the light might have chatoyance. Insect eyes are a different effect. Compound eyes are actually little conical tubes(?) with a little depth. Insect shells, well, is it iridescent or deeper reflective from more layers of ___(lost the word).

 

Great information on the trees to, Karl. I have three pieces of Koa, and will have a more close look at its qualities. Two are small, my sized, and curly, the other, I am not sure. I like scraps from other's larger projects. :blink:

 

Karl W. A metal person will have to answer that, but the fact that the layers alloy, or melt together, when too thin might be a limiter. David, how thick or thin were your layers? Would softer and harder mokume layers work, first of all, and if so, would that help result in the differentiation of the layers? Oh oh, metals questions on a wood thread! :rolleyes::blink: . Can the layers be of a composition that would be less likely to alloy completely with one another? If this leads to more than a little answering, it could go to the metals section for further discussion.

 

Dan, thanks for the really nice illustration of stains on the curly woods. I never thought that basswood could look so nice!

 

Janel

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Aloha

 

Janel, Dan - very nice images of your works. Reminds me to get busy.

There is a finish that I have been meaning to mention. It is MinWax Antique Oil Finish; a modified linseed alkyd resin with dryers. I've used it for years.

Benefits - High solids (34%) as compared to Watco. Overnight drying (though subsequent coats take longer). Fast build-up. Little or no reaction to water, alcohol or sweat. Will not easily redesolve in a solvent (like shellac in denatured alcohol). Has give to move with the wood.

Detriments - Imparts an amber color with build-up. Must be kept dust free during setup. Will fire off in the can unless repackaged in smaller units or resealed with Bloxegen.

 

KC

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Hey! Great responses!

 

Yes Karl, I think that Mother-of-Pearl and other shells that glimmer and glow in the light might have chatoyance. Insect eyes are a different effect. Compound eyes are actually little conical tubes(?) with a little depth. Insect shells, well, is it iridescent or deeper reflective from more layers of ___(lost the word).

 

Great information on the trees to, Karl. I have three pieces of Koa, and will have a more close look at its qualities. Two are small, my sized, and curly, the other, I am not sure. I like scraps from other's larger projects. :blink:

 

Karl W. A metal person will have to answer that, but the fact that the layers alloy, or melt together, when too thin might be a limiter. David, how thick or thin were your layers? Would softer and harder mokume layers work, first of all, and if so, would that help result in the differentiation of the layers? Oh oh, metals questions on a wood thread! :rolleyes::blink: . Can the layers be of a composition that would be less likely to alloy completely with one another? If this leads to more than a little answering, it could go to the metals section for further discussion.

 

Dan, thanks for the really nice illustration of stains on the curly woods. I never thought that basswood could look so nice!

 

Janel

 

I have had it appear in Mokume both iron Pattern weld mokume when slightly etched and a high layer count Nickel silver and copper Mokume. The Nickel silver layers were thicker and I etched the copper out to create a subtle raised grain. The effect was very nice. I have pictures of those parts somewhere, but you can't really capture the shimmering aspect of it with the camera and especially not the old digital camera I took this photo with hehe.

patrick

post-40-1182209632.jpg

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Aloha Janel,

Insect shells, well, is it iridescent or deeper reflective from more layers of ___(lost the word).

Chitin perhaps?

Will fire off in the can unless repackaged in smaller units or resealed with Bloxegen.

KC

Sorry, did not mean to go Chamarro on you. Most finishes of this type begin to polymerize with exposure to oxygen (or in the case of cyanoacrylates, water vapor). As you use the contents of a container, the empty space naturally fills with the O2/N2 from around us. This causes contents (especially those with metallic dryers like cobalt) to skin, then gel (fire off) in the can. Accordion type squeeze bottles suck. So I repack new cans immediately into smaller ones with as little air space as possible and/or give a shot of Bloxygen (which I mispelled) under the cover to displace the air. Composed of inert gases, it displaces the atmospheric stuff and being heavier, settles over surface of the liquid. Choose your repack containers with care. Avoid unlined metal or lid seals that melt upon exposure to petroleum distillates. Canning jars are great, but keep them away from light.

You may be interested in this reference, The Wood Handbook - Wood as an Engineering Material. Put out by the USDA Forest Service, it is available from Lee Valley Tools (Phil may have seen it). Subsidized by Uncle Sam, it is a tremendous resource at a ridiculously low price.

 

Patrick

Those pieces are ethereal. Could you find some way to include them in the mokume thread? I think they should be a part of that record.

 

KC

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Do you think it could be possible to gain suchlike effect with mokume or do this need a very large number of layers? (The number of layers in mokume is somewhat limited because the metals tend to alloy completely whem becoming too thin)

 

regards,

Karl

 

Karl,

 

I think it probably could, but it depends upon a number of factors. As a knifemaker I've only used mokume made from copper and nickel silver, not precious metals. Most of the makers of mokume for knifemakers use a set of squeeze plates to hold the metal strips together while fusing it. I have not used any that was soldered. As with damascus steel I believe it would need a relatively high layer count and a good etch and final finish. On certain patterns on damascus the end of the layer is exposed to your view. With a good etch that's deep enough to feel and see the topigraphical effect, and with polishing the top of the layers you can get chatoyance. If you can duplicate this in mokume it should work. However, I don't know what will happen once the copper or other metals tarnish.

 

I think the main reason people like mokume, at least what we knife guys use, is that it shows it's patterns as the metals tarnish, no matter whether it's satin finished, buffed, or etched. If you go for chatoyance you may loose the colors because you've got the layers so fine you can't really tell the brown copper from the white nickel silver. Chatoyant damascus "wiggles" around in the light because your eyes don't easily distinguish between the dark and light layers.

 

David

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Great information David, thanks!

 

Happy to help, Janel.

 

"I've found that using a spirit bases stain works better than an oil based stain. It is thinner and penetrates deeper."

 

Question 1- Must you be fastidious about working the surface to remove all scratches before using a darkening stain? I really dislike surprises, work at great length to remove scratches on the hardest woods, but maple, for instance, is softer than what I normally use.

 

DB.With any wood work you need to remove scratches so the stain won't highlight them. In high school wood shop (long ago when they actually had wood shop in schools!) we would sand to around 240 grit before staining, and that was usually fine. Many knives are made with a wood attached and sanded along side of a metal, and that metal needs a finer finish. The wood is pretty slick. I've used alcohol based leather dyes with good results. An oil based stain barely colors curly maple when it has a 600 grit finish! Maple comes in all hardnesses. Sugar maple is soft, but hard rock maple is properly named. The curly and birdseye maple I've used is usually fairly hard, more so than koa which works very much like walnut. I have sculpted maple handles and found that after roughing it with an abrasive rotary tool that files and sandpaper work well.

 

Question 2- Would thinning artist oil paint with mineral spirits or turpentine be equivalent to using spirit based stains?

 

DB. I have no idea. I've never used oils. Would be worth a try though.

 

"some of us just spit on it" - I thought I was alone with this! Mom taught us to spit on rocks while she was raising her little pack of rock hounds ;)

 

DB. Saliva, the ultimate solvent, cleaner and wetting agent! I spit on wood and rocks all the time. Not everyone, though, as the same appreciation for this technique as we do!

 

"curly maple that is sawn and planed, and it's rough with raised curls" This is a good bit of information to consider. I really like the looks of curly maple, but fear committing a piece to it if there is much carving, so if some carving is done with a rotary tool, maybe there might be fewer complications with the grain and smoothness? Something to try, at any rate.

 

DB. I recommend you try it. If you are emphasizing your carved details then a wood like ebony or black wood with little figure are better, but if you are doing something larger without tiny details then the figure may go well with your carving. Maple comes in many types of figure, such as the quilted figure in Dan's picture. Curls, birdseye, feathered crotch, burls, curly burls, curly burly birdseye, and spalting. Machined wood can have some grain raised, but these woods that have been mentioned sand very well. If you are using chisels just make sure they are sharp. Maple is a lot tougher, not as brittle, as ebony, and you've carved ebony with success.

 

"I usually give wood a tung oil finish of many layers" How many layers? I have not been happy with its use, but maybe I am not using it right, or have not been patient enough to build up many layers... I also want a surface that won't be affected by moisture from sweaty hands, or worse.

 

DB. The koa on my Persian Stiletto probably had as many as 15 coats. The first one dries in about 10 minutes because the wood is so dry. Use it very sparingly. I sometimes just put a drop on my finger and spread it around and work it in. Between coats I scrub it with 0000 steel wool. As you build layers use the steel wool lightly, just enough to dull the surface. Walnut takes about as much as koa, but maple will take less. I feel a penetrating finish enhances the chatoyance better than a surface finish. You can give the wood a few coats of tung oil for that reason, then coat the wood with a polyurethene finish for better protection. You can also wax it. I prefer Formby's tung oil and Renaissance Wax.

 

The damascus steel chatoyance must be wonderful to experience! Is this something that you can repeat with enough layers and and layer movement?

 

DB. It really is cool! When I order billets of damascus for my knives I almost always request higher layer counts. For one thing the pattern is not so loud as to compete with my sculpting, but also because of the "wiggle" of the chatoyance. Go to this page http://www.david.broadwell.com/spknife.htm and look at the handle on the top knife, the balisong. I used a fine tight ladder pattern on it, etched as deeply as I could, burnished with steel wool, then just kissed it with the buffer. It looks a lot like curly maple with a gray stain on it, and the "curls" shift back and forth. It take fine layers with those layers going from a side view to an end view and back again to get this look.

 

Chatoyance is difficult to capture and show in photos, but it would be great if the members might give it a try with posting images of it in our work. I'll start and give it a try:

 

DB. Janel, your dragonfly carving is outstanding! My wife saw it and her jaw hit the floor. She had me send them to her surgeon who likes dragonflies and other bugs. The base show a nice amount of chatoyance, and is perfect for your theme. The bug is sitting on the grass, and they are above the rippling of the water. Ok, the water may look a little muddy, but it's still fluid. This is not a stagnant piece!

 

Hope this helps. (Read between the lines for my answers.)

 

Beautiful mokume pieces, Patrick. Your description of the technique you used sounds perfect for showing chatoyance.

 

I love mokume. Wish it was more popular among knife collectors right now. Makes very interesting jewelry though.

 

David

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I am beginning to wonder if I will make it to the studio at all today!

 

Thanks David, for the above responses. Thanks to your wife too, and I hope her surgeon does jaw surgery if she needs it now :D;)

 

The links to the knives are a good illustration of high layer count, and it has a feel of flowing water in the top image. I look forward to meeting some damascus steel now, after these discussions on TCP.

 

When sanding boxwood, I go to 400-600 grit to remove scratches, wet it and go over it again. The faint scratches are hard to see. Water will raise the grain and compressions, and help for attaining a smoother scratch free surface. Patience is the key at this point. The scratches will always show up after the color is applied if not taken care of. If the piece is to be polished, the grit number goes higher. Same for the hard more resinous woods that self polish.

 

Thanks for the tung oil tips. I know now that I am too generous from the start. One thing I am glad to learn that I wanted to learn, is that one can coat the wood with a polyurethene finish. The maple water was treated sort of like that. I used a penetrating finish applied in fine, multiple applications, but was too soft for my wishes, and showed hand moisture. I applied an oil urethane (I think that was what it was) over that in fine multiple applications until it did not stick any longer. Nerves with that piece!!!

 

I have some different maples. I look forward to putting tools to them now.

 

Thanks,

Janel

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Aloha David,

 

Wow. ;) That was really cool. I've never seen a reply inside a quote before. Very efficient.

Better protect your koa source. Prices just jumped an average of 15% across the board. An order for 5000 bf was recently shipped out by air to Rhode Island. I estimate it at a quarter million dollars US.

Somebody must be buying mokume and using it. Mike Sakmar is moving to larger digs for the 2nd time. He even skipped Atlanta this year.

 

KC

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Hi Janel,

 

I am familiar with the book that Karl is refering to. It is very good, and not expensive. Lee Valley tools also sells a similar product for keeping your oil-based finishes from hardening.

 

I have been interested in usung curly-grained woods for some time. However, I often like to concentrate on form, and find that the grain can take away from what I am trying to do. I have had some success with doing some low relief carving, with simple designs. I carved the piece below, about 4 years ago, in curly maple from a flitch that was split and joined. The designs have a punched background to emphasize the positive and negative spaces, and break up the curly grain.

 

I believe the only sanding that I did was a very quick pass with some 220 paper, the rest was done by burnishing. The stains are a combination of 3 aniline water-based stains, which are applied separately allowed to dry, and cut down with 4/0 steel wool between coats. The finish started with a 1:1:1 linseed oil/oil-varnish/mineral spirit wash that is brushed on and allowed to soak in, then wiped off. I then add a bit of lamp black after the finish has dried, directly to the surface by brush to accentuate the background. The final finish is polymerized tung oil, followed by pigmented wax.

 

The piece is inspired by an early Anglo Saxon design from the Lindisfarne gospels (actually adapted from a letter "O"). It is about 18" long.

 

post-1087-1182300104.jpg

 

post-1087-1182300128.jpg

 

Best regards,

 

Phil

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Hope this helps. (Read between the lines for my answers.)

 

Beautiful mokume pieces, Patrick. Your description of the technique you used sounds perfect for showing chatoyance.

 

I love mokume. Wish it was more popular among knife collectors right now. Makes very interesting jewelry though.

 

David

 

Hi David,

There has been a decline in sales for Mokume fittings. I used to make a lot of them, but the last set I put up sat around way too long.

Karl,

I have not had problems with the Copper and nicklesilver completely blending. I use Solid state bonding and my temps are digitally controlled so the weld zone is very crisp even after many anneals. Of course I only tried this fine a layer count with the Copper and nicklesilver combination. Other blends may very well difuse away all contrast if worked to the same degree.

patrick

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Thought I would put in my experience as well.

 

Alcohol based stains work well and so do some dyes. I use dyes from a local leather shop and they work great. They are also useful for recreating antique finishes. They are transparent where the oil based stains are little muddy. A look like the carving of Phil's is easy to achieve with the leather dyes.

 

Oil finishes always depend on the sanding beforehand. The better the sanding the better the finish (not a finish for those who hate to sand).

 

Most of my work is finished with lacquer but small pieces with beautiful grain are getting the oil treatment. Like Phil I use a oil blend on my hand rubbed finishes. Basically the same blend although I substitute spar varnish for UV protection and the extra solids content. As said the more coats the more sheen and the longer the drying time between coats. It is a beautiful finish and is durable. I finished an entry way door carved in mahogany 15 years ago and the finish has been reapplied only 3 times and it is still beautiful.

 

Had to say how beautiful the work is that has been posted here. Really nice. Inspiration at my fingertips on this forum!

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Guest ford hallam

Hello all,

 

fascinating topic :) , almost makes me jealous of the woodies :D .

 

There does seem to be a misunderstanding here though, regarding what appears to be a similar effect in mokume type patterned metal.

 

Chatoyance ( cat's eye effect~ from the French; Chat, meaning cat, and oiel, meaning eye )

""this is caused by the reflection of light by parallel fibres, needles or channels." from Gemstones of the World, Walter Schumann. This was one of my handbooks for the gemological aspect of my goldsmithing apprenticeship.

 

The phenomena when seen in wood is essentially the same as seen in gem stones. The most well know stone exhibiting this effect is probably Tigers Eye.

 

The effect that has been commented on with regard to mokume, or patterned metal, is a very different thing.

The surface of metal is not translucent ( sadly :) ) so the effect seen on metal is confined solely to the surface. Unlike with wood or gems where the effect depends on a certain degree of depth.

 

One of the earlier terms used to describe this shimmering effect in metal is the French word Moire, which originally referred to the effect in fine textiles particularly silk. The fine patterning found in some Persian blades is frequently ( at least in older books) described as watered steel ( possibly from watered silk and alluding to a surface of shimmering water ) or Moire steel.

 

The moire effect is a purely surface "optical illusion" sort of effect which results from the interplay of two set of misaligned, finely spaced, parallel lines. The most common use of the term now ( to describe exactly the same phenomenon ) is to describe the interference pattern that often appears in scans ( into your pc. ) of printed images. Chatoyance can't be achieved like this.

 

So, as much as I, as a metal lover ;):) , would love to see true chatoyance in metal I would have to say that we must be content with our own special effect, moire. I think it sounds sexier anyway :D;)

 

Namaste, Ford ( pedantic semantic smiley)

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Guest ford hallam

I noticed a reference to the characteristic "shimmer" in mother of pearl being similar to Chatoyance earlier too. This is Iridescence and a very specific, and different phenomena.

 

This is the entry from Wikipedia, hope it clarifies things. ;)

 

"Iridescence is an optical phenomenon characterized as the property of surfaces in which hue changes according to the angle from which the surface is viewed (as may be seen of soap bubbles and butterfly wings). [and in mother of pearl, or nacre. my addition]

 

Iridescence is caused by multiple reflections from multi-layered, semi-transparent surfaces in which phase shift and interference of the reflections modulates the incident light (by amplifying or attenuating some frequencies more than others).

 

The word is derived in part from the Greek word iris (pl. irides), meaning "rainbow", which in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods."

 

regards, Ford

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Hello all,

 

fascinating topic :) , almost makes me jealous of the woodies ;) .

 

There does seem to be a misunderstanding here though, regarding what appears to be a similar effect in mokume type patterned metal.

 

Chatoyance ( cat's eye effect~ from the French; Chat, meaning cat, and oiel, meaning eye )

""this is caused by the reflection of light by parallel fibres, needles or channels." from Gemstones of the World, Walter Schumann. This was one of my handbooks for the gemological aspect of my goldsmithing apprenticeship.

 

The phenomena when seen in wood is essentially the same as seen in gem stones. The most well know stone exhibiting this effect is probably Tigers Eye.

 

The effect that has been commented on with regard to mokume, or patterned metal, is a very different thing.

The surface of metal is not translucent ( sadly :) ) so the effect seen on metal is confined solely to the surface. Unlike with wood or gems where the effect depends on a certain degree of depth.

 

One of the earlier terms used to describe this shimmering effect in metal is the French word Moire, which originally referred to the effect in fine textiles particularly silk. The fine patterning found in some Persian blades is frequently ( at least in older books) described as watered steel ( possibly from watered silk and alluding to a surface of shimmering water ) or Moire steel.

 

The moire effect is a purely surface "optical illusion" sort of effect which results from the interplay of two set of misaligned, finely spaced, parallel lines. The most common use of the term now ( to describe exactly the same phenomenon ) is to describe the interference pattern that often appears in scans ( into your pc. ) of printed images. Chatoyance can't be achieved like this.

 

So, as much as I, as a metal lover ;):D , would love to see true chatoyance in metal I would have to say that we must be content with our own special effect, moire[/i]. I think it sounds sexier anyway :):)

 

Namaste, Ford ( pedantic semantic smiley)

 

Of course it is not the same mechanism. I hope people did not think that mokume is translucent or transparent :D hehe

Chatoyance was just the closest thing I knew to describe the effect. Moire is interesting How exactly does one pronounce it? Until I know I can't confirm it sounding sexy or not :)

patrick

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Guest ford hallam

Hi Patrick,

 

I stand to be corrected by our French members but I say; " moy ray". The sexyness comes from the hint of a French accent I use with this word ;):D , but then again, I'm such a tart :)

 

Cheers, Ford

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Thanks Ford for the definitions of the differences in materials and structures which result in very similar and admired light reflection effects. So, because the gleam of mother-of-pearl is made of layers of translucent material (correct so far?) its reflection of light is irridesence, and not chatoyance which is a result of light reflection off of parallel elements (edges or perhaps strands?) in the material? And moire describes the light reflection events from the minute differences in height of the surface edges of the layers of the etched and polished metals (or other materials of different surface height, such as cloth, which is reflective)?

 

Minute differences with, similar but different, attractive light interaction. Very interesting!

 

Is the mother-of-pearl nacre laid down in layers, which would result in undulating parallel layers, which on edge are not reflective? I cannot remember if it works that way. I have to go cut and polish some to see. So, the light reflection off the layers of beautifully translucent nacre is not chatoyance? Until now, I thought that irridescence was a reflective surface effect and not a deeper translucent material effect. Mineral chatoyance results from some degree of translucence in the material?

 

Where do opals fit into this?

 

My waking up morning brain has questions about these light reflection details! Thanks for the push towards greater understanding. ;):)

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Guest ford hallam

Hi Janel,

 

I think you've pretty much got it. The Moire effect on metal can sometimes have an element of actual physical texture, which would add to the effect, but isn't essential.

 

Nacre is, as you said, laid down in layers, that's how pearls form, as layers of nacre secreted by the clam to surround the tiny irritant grain of sand. Cultured pearls are started with a much larger bead of mother of pearl being placed in the clam.

 

Opals exhibit a characteristic rainbow like iridescence which changes with the angle of observation called opalization. ( not to be confused with opalescence, that pearly/milky blue appearance of common opal, which is caused by the reflection of short waves of light, mainly blue ). Opals contain tiny spheres of a mineral called cristobalite which are layered in a siliceous jelly. These tiny spheres reflect light and also cause interference in the transmission of light passing through the gem. This is what we see as the result of opalization

 

All these different terms and effects have very specific scientific definitions and all sorts of clever formulae and light effect analysis which distinguish them from one another.

 

It would probably help to have a better description of chatoyance as it appears in wood.

 

Ford

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