A Color Chart for the Thin Film Color Progression

Sunnywood

In these threads, I discussed the thin film interference effect, and a proposed color classification system.

Towards an understanding of the color progression on toned coins ...

A proposed new classification system for toned coins

The occurrence and appearance of golds and yellows on toned coins

Now I am introducing a simple color chart to go along with with classification system. This will help as a roadmap or guide to the expected toning colors along the progression. I created this in a spreadsheet, and the colors are only approximation to what we actually see on the coins. So think of this simply as an aid, or guide, and not as gospel. After looking at hundreds of colorfully toned coins using this chart as a reference, you begin to really understand what you're looking at, and what these colors look like "in real life." I hope some of you find this as useful as I have.

lope208

I'm a visual learner. Thanks for the chart

Sunnywood

Here are some examples. When the toning covers a wide portion of the spectrum, sometimes the individual colors can be in very narrow bands, and the toning may seem to skip over a color here or there. This all depends on the slope of the toning curve, i.e. how quickly the toning layer thickness changes as you move across the surface of the coin. Conversely, some coins will be toned predominantly in just one or two colors, indicating that the toning layer is of relatively uniform thickness.

RunnersDad

Thanks Sunnywood, this chart really helps to put it in perspective!

Sunnywood

Like banded rainbow toners, target toners are also usually easy to classify, with the toning running from the center (least toned; lowest color class) out to the perimeter (most troned; highest color class):

STONE

Sweet, I never knew there were so many toning colors out there, and it's a perfect alphabetical fit!

kryptonitecomics

very helpful...thanks for sharing

Sunnywood

Sometimes the colors intermingle, and do not look like the corresponding colors on my chart. For example, this 1892-CC PCGS MS66 Morgan has an obverse that ranges from burgundy (E) in the recesses on the left edge of Miss Liberty's portrait, through cobalt blue and cyan, and into pale mint green with touches of color out to sunset yellow. So it is in the range from E to J. The reverse is a hair further along in the progression, with scattered cobalt blue (F) ranging out to orange (K). So the whole coin, both sides, falls in the range of E to K on the chart. But if you look at the chart, you'll see that it's a poor approximation of what the coin looks like. Still, the chart is very useful, and allows you to put the toning on this coin into the proper context.

sinin1

thank you for all your work and contributions to numismatics


my personal preference is for toned coins

as far as I am concerned, they are like a nice painting versus a black and white photograph

topaz77

Very interesting and educational. Thanks for sharing.

Franklinwho

very interesting. i went through some of the links to previous posts u wrote, very detailed/informative and a bit complex for a novice (me ). i will reread many times to hopefully get the entire point correctly. thank you for your hard work on putting this together. now if i could figure out whats at/nt i would be set lol.

fc

so basically you have taken a color chart of thin film interference,
slapped some letters on it an key points, and consider it part of a
classification system for toned coins?

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

then to call this the sunnywood classification system instead of Physics 101
that freshman take in college?

got it.

Fairlaneman

Sunnywood what is this one?



EDIT to ADD: Thanks Much for the chart today and the one from a few weeks ago.

Thanks.
Ken

Sunnywood

<< <i>so basically you have taken a color chart of thin film interference,
slapped some letters on it an key points, and consider it part of a
classification system for toned coins? >>



Yes, that's quite right. It gives us a convenient system of reference and nomenclature. And it's an extremely useful tool for anyone who collects and studies toned coins, and is interested in the science and the chemistry. It beats just saying, "Ooh look at the pretty colors" without knowing what they are and where they come from. And I don't believe anyone has applied this quite so directly and clearly to colorful toning. (By the way, what would you have said to Sheldon?)

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

Not aribtrary at all. This follows the conventions used in thin film coatings for optics. Because blue is the shortest of the cone receptor-specific wavelengths at 220 nm, the oscillation between cancelling and reinforcing blue light occurs more frequently than the other primary colors. Therefore, it is the constructive-destructive interference for blue that is used to mark the cycles. The reason that toning starts with golds is that those colors represent cancellation of blue light, which occurs first since it is the shortest wavelength.

then to call this the sunnywood classification system instead of Physics 101
that freshman take in college?

Yes, I enjoy putting my name on my work, wouldn't you? There is nothing new about the thin film interference color progression, but I don't think anyone has gone quite as far in applying it to the colorful toning on coins. I don't think college freshmen study rainbow-toned Morgan dollars. At least I didn't when I took Physics 55 freshman year at Harvard. I'll be happy to support your creative contributions under your name, when you make them.

Best,
Sunnywood

Edited to add: Ken, small diameter coins, especially those that have been in albums, tend to get covered more quickly with toning as it encroaches from the perimeter, and therefore often fall deeper into the progression, with colors that cover the entire surface. A larger coin, stored under the same conditions, would likely have more differentiated target toning. When trying to classify a color, it helps to look at the hints of other colors nearby, for example in the recesses of the devices. In this case, while it's always hard to be certain from an image, it appears that the predominant color is class R, which I call "emerald green" (although in this case, it appears darker than on some of the Morgans I used to demonstrate above). There are subtle hints of the colors that come both before and after class R, if you study the coin carefully.

TONEDDOLLARS

Great answeres Doug. I like a man who can back up his presentation with logic.
Thanks for the time and effort.

fc

<< <i>

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

Not aribtrary at all. This follows the conventions used in thin film coatings for optics. Because blue is the shortest of the cone receptor-specific wavelengths at 220 nm, the oscillation between cancelling and reinforcing blue light occurs more frequently than the other primary colors. Therefore, it is the constructive-destructive interference for blue that is used to mark the cycles. The reason that toning starts with golds is that those colors represent cancellation of blue light, which occurs first since it is the shortest wavelength.

>>



maybe i am confused. blue and 220 nm? 220 nm is ultraviolet light. maybe you meant 420 nm range which is blue/violet?

when you say cone receptor and 220 nm... i just do not get it. we cannot see light at 220 nm. 380 nm is the lowest.
and yes, 420 nm is the most sensitive to S cones.

But if what you say is true about blue being used to mark the cycles that makes sense why you choose them.

kryptonitecomics

<< <i>so basically you have taken a color chart of thin film interference,
slapped some letters on it an key points, and consider it part of a
classification system for toned coins?

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

then to call this the sunnywood classification system instead of Physics 101
that freshman take in college?

got it. >>



As far as toning is concerned...do you ever have anything positive to say or do you just like to pee in everyone's corflakes on a consistant basis? I for one don't know what I would do without your useless but consistant toning comments on a daily basis

Sunnywood

Ah yes, fc, you are quite right. Our "blue" cone receptors have peak sensitivity at 440nm, which is blue light. The 220nm figure represents the corresponding thin film thickness to travel that extra distance (since it's a round trip through the film and back out again). I explained this correctly in one of the other threads ... so yes, I should have said 440nm in the above post, not 220. Good job catching the error !

fc

<< <i>

<< <i>so basically you have taken a color chart of thin film interference,
slapped some letters on it an key points, and consider it part of a
classification system for toned coins?

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

then to call this the sunnywood classification system instead of Physics 101
that freshman take in college?

got it. >>



As far as toning is concerned...do you ever have anything positive to say or do you just like to pee in everyone's corflakes on a consistant basis? I for one don't know what I would do without your useless but consistant toning comments on a daily basis >>



someone just took a chart and slapped some letters on it and all of a sudden
one calls it the sunnywood's color classification chart system for toned coins and you think this is somehow
enlightening?

how about i pick a range of numbers, lets say, 1-25 and create a new grading scale.
i will dub it fc's grading classification chart system. i will expect you to suck up to it.
ok?

sunnywood is a big boy and he can defend himself from my harsh criticism just fine.
he explained his cycle aspect nicely. if the system is good it can withstand
some criticism and who knows... discussing it might help people
understand it better then just bowing down to the toning god (sunnywood).

i hope you do not mind me calling you the toning god sunnywood.
i am sure your cult members will agree


Great answeres Doug. I like a man who can back up his presentation with logic. Thanks for the time and effort.

it helps if you understand them and can notice the mistakes though.

but a cult will not notice mistakes with their god and blindly accept
the gospel according to sunnywood!

sorry. could not resist.

Barberian

fc, you sound like all the scientists I see that are jealous of another's accomplishment. Sure, you could have done the same thing easily enough. Why didn't you? Sorry, but Sunnywood gets credit for posting it first. Come up with your own system, "publish" it, and we'll all see which one gains widespread acceptance.

MikeInFL

<< <i>

<< <i>

<< <i>so basically you have taken a color chart of thin film interference,
slapped some letters on it an key points, and consider it part of a
classification system for toned coins?

Then arbitrarily choose which colors represent a cycle based on where
blue seems to repeat instead of say gold/yellow which clearly starts off
the chart and repeats too?

then to call this the sunnywood classification system instead of Physics 101
that freshman take in college?

got it. >>



As far as toning is concerned...do you ever have anything positive to say or do you just like to pee in everyone's corflakes on a consistant basis? I for one don't know what I would do without your useless but consistant toning comments on a daily basis >>



someone just took a chart and slapped some letters on it and all of a sudden
one calls it the sunnywood's color classification chart system for toned coins and you think this is somehow
enlightening?

how about i pick a range of numbers, lets say, 1-25 and create a new grading scale.
i will dub it fc's grading classification chart system. i will expect you to suck up to it.
ok?

sunnywood is a big boy and he can defend himself from my harsh criticism just fine.
he explained his cycle aspect nicely. if the system is good it can withstand
some criticism and who knows... discussing it might help people
understand it better then just bowing down to the toning god (sunnywood).

i hope you do not mind me calling you the toning god sunnywood.
i am sure your cult members will agree


Great answeres Doug. I like a man who can back up his presentation with logic. Thanks for the time and effort.

it helps if you understand them and can notice the mistakes though.

but a cult will not notice mistakes with their god and blindly accept
the gospel according to sunnywood!

sorry. could not resist. >>



FC, It is one thing to constructively criticize a theory. It's another thing entirely to be mean-spirited in your criticisms. You are smart enough to know the difference, and Sunnywood did nothing to draw your ire, IMO. Respectfully....Mike

MikeInFL

p.s. thank you, Sunnywood, for posting this info. I find it very helpful to see the color progression in a table as you have presented.

streeter

I sure appreciate this thread. Heck I don't even remember my Physics 10 from Berkeley 37 years ago.

fc

i just wanted to be clear on what sunnywood was posting.

a thin film color progression chart with letters at key places with blue
being the boundaries of the cycles.

a classification system that is basically unuseable in normal conversation or
even in plain english writing when discussing toned coins. As
another poster said in a previous thread: "You have come to a fairly
complicated solution that seems to be in search of a problem."

something that has been discussed to death on this forum since the
first year it started. (feel free to search. it was discussed in more detail
back then too).

I guess the point of this forum is not to criticize an idea that, frankly,
is too complicated for any regular usage but to blindly praise the effort
and thought that went into it without consideration of the idea itself.

So if posting a color chart is worthy of praise wait until i develop my
dirty gold chart showing the layers of patina, A-Z, with consideration
for partial patina patterns and the crevice angular holding factor.

Sunnywood

fc, you give me too much credit - my legions of worshippers probably don't include anyone besides my dog and my mom. In fact, when I first proposed a classification system for toning, it was pretty much shot down as being unnecessary, even by those who specialize in toned coins. However, I was not discouraged. I have found that the classification system really helps me to bring the whole picture together, and has enhanced my understanding of my own coins greatly. I find it very worthwhile to make sense of the myriad and seemingly random color patterns on toned coins.

I only want to share that same knowledge, insight and understanding with fellow collectors. I am sure there must be at least a small handful who will find all of this as interesting as I do, including the chart with the letter designations, which I find particularly useful. By the way, this work is quite usable in written or spoken conversation, with others who have a working familiarity with its terms. In time, there will be more of us.

I didn't expect there to be wide interest, or universal adoption - far from it. I just put it out there for whoever might be interested, that's all. If the idea offends you, by all means don't make use of it. I can assure you that I am not bothered in the least, not even by repeated criticism that borders on intentional insult.

Now, enough of all that ... here's another walk through the colorful world of toning:

Sunnywood

... and for something a little different visually, here are some of my old Barber quarters:

fc

<< <i>fc, you give me too much credit - my legions of worshippers probably don't include anyone besides my dog and my mom. In fact, when I first proposed a classification system for toning, it was pretty much shot down as being unnecessary, even by those who specialize in toned coins.
>>



Thus what i am saying in this thread is nothing new and I am not
alone with my thoughts.



<< <i>However, I was not discouraged. I have found that the classification system really helps me to bring the whole picture together, and has enhanced my understanding of my own coins greatly. I find it very worthwhile to make sense of the myriad and seemingly random color patterns on toned coins.
>>



a simple color chart without the classification letters would have worked
just as well.



<< <i>I only want to share that same knowledge, insight and understanding with fellow collectors. I am sure there must be at least a small handful who will find all of this as interesting as I do, including the chart with the letter designations, which I find particularly useful. >>



This has been discussed going back years on this forum in just as
great detail. Nothing new here except the lettering.



<< <i>By the way, this work is quite usable in written or spoken conversation, with others who have a working familiarity with its terms. In time, there will be more of us. >>



It seems the only use it has so far is in pictures as shown in your post
above which even then turns into alphabet soup and without the chart
totally useless. I doubt people will memorize so many letters to colors/cycles.



<< <i>I didn't expect there to be wide interest, or universal adoption - far from it. I just put it out there for whoever might be interested, that's all. If the idea offends you, by all means don't make use of it. I can assure you that I am not bothered in the least, not even by repeated criticism that borders on intentional insult.
>>



It hardly offends me. I just think it is a poorly thought out idea is all.

And please make note that this is the first time i have replied in one
of your toning progression threads. It appears all the disenters have
already spoken on the topic and moved on.

I suppose i will do the same now.

Sunnywood

It hardly offends me. I just think it is a poorly thought out idea is all.

Yes, as I said, intentional insult - and without merit. I can be accused of many things, but having poorly thought out ideas generally isn't one of them. And really, didn't anyone ever tell you that it is quite frankly rude, obnoxious and unnecessary to say such things? You could simply have refrained from posting at all if the idea had no merit to you.

It appears all the disenters have
already spoken on the topic and moved on.

I suppose i will do the same now.

Well, thank Goodness !!

Here is another mapped out coin, just to cleanse the thread:

MacCrimmon

Thanks Sunnywood for keeping me from going back in time 33 years to dredge up TFI physics.


P.S. Those LETTERS on your superb Morgans and Barbers give me goose bumps.

ColonialCoinUnion

Not my area of specialty, Doug, but I found this very interesting - thanks for posting it.

SeattleSlammer

wow, i guess fc is having a bad day?

anablep

I love this stuff.

Great chart. I'm going to print & laminate this thing for reference.

Thank you Sunnywood...

EagleEye

Thanks for posting! I nominate it for Post of the year!

rjsvt

I am not a collector of toned coins, but I do find this post very interesting. I’m in the semiconductor industry where film thickness is measured on silicon wafers. It's done by correlating film thickness to the surface color of the silicon when lit by different color lights. If I understand what you are saying, you're pretty much doing the same thing.

I'm curious what a map of the film thickness of one of your coins would look like (after removing the coin details and just plotting the thickness as indicated by color). Here's one of some silicon.


Since the order of letters (classifications) you put over the coins indicate a smooth transition in thickness, I'm guessing the film thickness map would look smooth as well. It might emphasize how a very small and smooth transition in film thickness can cause a drastic change in color (seen in your color chart but not as easy to visualize when looking at the coin). What's the value to it? I have no idea. I suppose you could predict what a coin will look like if the film continues to thicken. Or maybe the film growth patterns would indicate something (leak in the slab, or help to ID doctored coins?).

Just my two cents. And thanks for all the work you put into this.

bob

lope208

Sunny,

Forgive me if I missed this in your initial post on this topic, but the one
potential downside I see to this is--just like the TPG's--it seems subjective based
on one's interpretation of color.

For your system to become more widely used, how do we eliminate, or at least
diminish, the inherent subjective nature of viewing colors?

coindeuce

POTY, excepting the responses of one.

Sunnywood

Thanks for all the positive responses!

rjsvt, the color distribution on the coin's surface is essentially equivalent to a film thickness map. The way the colors do generally flow smoothly along the progression shows that it is a continuous, well-formed surface. Of course the slope can vary, so you can have steep areas where the color changes rapidly. The incoming light, along with our own eyes' ability to process it as perceived color, is equivalent to having a film measurement device that outputs a color-coded map.

lope208, this is not really subjective in theory, as there is a specific film thickness that is theoretically measurable. But, in practice, it can be a little difficult. I have some coins that display, for example, magenta to blue to green, where I'm not sure whether it's EFGH color, or MNPQR color, or TUV color. Usually I can tell, but there are some rare exceptions. In theory, it could be measured though, to get the correct answer - as every color class on my chart corresponds to a specific range of toning layer thickness.

Also, there are some chemical environments that can alter the color scheme somewhat, for example by introducing molecules into the toning layer other than the usual amounts of oxides and sulfides. So for example if there was chlorine around, some of the colors might look different. Therefore, the historical packaging for certain series (e.g. cellophane) will result some different "looks" to the coins. In addition, if the substrate metal is gold or copper, which have their own "color" (i.e. they absorb certain wavelengths of visible light on their own), then the progression may look different on those metals. Surface quality and finish can also affect how vivid the colors look. So there are variables. But for now, by sticking primarily to album-toned silver and rainbow bag-toned Morgans, I am finding that the color chart is quite universal in its applicability.

Best,
Sunnywood

P.S. I never envisioned this being adopted by a TPG ... it was just meant as a way to talk about, map out, and understand the color on these coins !!

illini420

Very interesting. Thanks for posting.

PCcoins

I have enjoyed this toning "color chart" since Sunnywood first showed us. I think you should write a book on it and show plenty of high quality images, I would buy it.

I think this color classification has had a lot of thought put into it by Sunnywood, and has done an amazing job IMO. It's a shame that someone has to bash it, if someone doesn't like it move on and ignore it! And let the other hundred members enjoy it!

Just my 2c

Goldbully

<< <i>In these threads, I discussed the thin film interference effect, and a proposed color classification system.

Towards an understanding of the color progression on toned coins ...

A proposed new classification system for toned coins

The occurrence and appearance of golds and yellows on toned coins

Now I am introducing a simple color chart to go along with with classification system. This will help as a roadmap or guide to the expected toning colors along the progression. I created this in a spreadsheet, and the colors are only approximation to what we actually see on the coins. So think of this simply as an aid, or guide, and not as gospel. After looking at hundreds of colorfully toned coins using this chart as a reference, you begin to really understand what you're looking at, and what these colors look like "in real life." I hope some of you find this as useful as I have.

>>




Sunnywood's colorful 'quad-thread'........2009's CU U.S. Coin Forum's multiple thread of the year!!!!

Remember these great threads this 2009 Christmas holiday season!!!

mrearlygold

Incredible little round artworks

asheland

Great thread as always!

BlindedByEgo

Sunnywood, while it may be said that you did no more than apply freshman physics to the discussion of coins, I appreciate that you did so. One could also say that Ford did no more than apply already known information to the manufacture of cars, or Gates to the design of software.

Knowledge without practical application is as useless as cojones on a mannequin; critics are a dime a dozen and contribute nothing.

I shall say no more as I have in the past been accused of being overly harsh on the poor, downtrodden and misunderstood, and have no desire to be so accused again.

Thank you for your contributions here, sir.

coindeuce

"If at first the idea is not absurd, then there is no hope for it". Albert Einstein

mr1874

....and the crevice angular holding factor.

Does this have anything to do with e equals mc squared?

pmac

Sunnywood has applied what he has learned to his passion - toned coins. Personally, I enjoy looking at his collection of toned coins. I bet it will spoil the toning when he tried to take all those little letters off his toned coins.

sebrown

Thanks Sunnywood. One of the more informative threads that I have read on this forum. It will definitely be added to my favorites of numismatic educational links.

jmski52

Sunnywood, this discussion and the science involved may not be new but the application of it is what's valuable in the long run.

You are taking the question another step and it is much appreciated that you are doing this. It's not that someone else couldn't have done this - it's that no one else has taken the time and effort to do so.

Since my own time is limited by other constraints, it's nice to see a field being developed for everyone's future benefit and future reference.

As to the lettering system, it's a tagging system that helps map out the coin images in order to make better sense of what is in front of you. Great idea! How else would one do it - microscopic notes overlaid on the image? NOT.

Since you are giving this much more thought than most, I'll ask you the question - do you think that AT can be identified by the toning characteristics?

2nd Question, would you map these two for me?

TypeCollector

<< <i>"If at first the idea is not absurd, then there is no hope for it". Albert Einstein >>

In that case, this idea is pure genius

Sunnywood

Small diameter coins can be a challenge, as there isn't enough room to have easily differentiable colors, and they tend to get more heavily toned in albums than their larger counterparts, as the peripheral rim toning reaches the center faster. But these two are easy:



Moderns, especially those that were in the cellophane Mint set packaging, can get very vivid colors, and that can make it very difficult to determine which cycle you're in. On some moderns, the earlier cycle colors EFGH can be so vivid that they resemble later colors like MNPR. I have much more experience with Morgans and 19th century album-toned type, so I need to study more Washies and Frankies to understand the modern colors better. Here's an example of a detail from a 1957-D quarter, right-facing wing, that illustrates the problem (using your "microscopic notes" idea !!):



(The answer, I think it is H and R, because to the right of band #2 we have a light gold, probably class S, which I wouldn't expect to see quite so clearly after class V.)
Here's the whole coin, with my best guess as to what's actually happening:



The rim toning on the reverse is least at about 2 o'clock, where it only gets out to K or L (red), but as you go down the right rim, you see that thin red band move in from the edge. Down at DOLLAR it runs through the middle of the letters. Over on the left side, at U of UNITED, it is at the bottom of the U. Beyond the red band, you see a thin band of green (R), an then another red band (T). The bands are too narrow to label them all properly on the image.

Until I learn more and gain more experience, I am most comfortable on Morgans (because I have seen thousands of them), and less comfortable on moderns (because I have never collected toned moderns). Perhaps the worst series in terms of toning on silver is Peace dollars, due to some aspects of their manufacture. By the way, the mapping takes time in Photoshop, and uploading & linking etc, so please don't be put off if I can't respond to every request for mapping !!

Thanks,
Sunnywood

Sunnywood

Here's a neat coin that I just mapped. This is like "paint by numbers" in reverse; you give me the painting, I fill in the numbers (ok, letters in this case). For those who say this system can't be used for a verbal description, here's my verbal description:

"A superb example of toning deep into the color progression, this coin exhibits copious fourth cycle colors (deep forest green and deep magenta) on the upper half, while vibrant class T magenta dominates the lower half. Small amounts of emerald green (class R) are seen between the digits of the date, and at stars 2-3-4-5. The remainder of the green on the coin is all forest green, class V. Textile in the left field sports emerald green dots on a gold/magenta backdrop (R dots/ST background), while on Miss Liberty's neck we see vibrant 3rd cycle gold dots on a magenta backdrop (S dots/T background). With toning ranging from class Q to class X, this coin demonstrates that even deep into the progression, we can have wild and vibrant colors on a classic bag-toned Morgan dollar."