Grade this 1838 half

Then where did the brown on the Half come from?

 

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Which one?

 

The OP coin; I'm not questioning either your knowledge or your opinion of the coins you posted. I see two different stages of toning on it (the OP coin), one of the factors in my diagnosis of it (the minor one, the major one being surfaces which have been eaten away) as having been harshly treated. This doesn't mean I don't think it required that harsh treatment, for the record.

I'm parsing you as disputing my thinking that two separate toning events occurred on it, and that's what I'm discussing. If I'm reading you wrong, let me know. The worst that happens is I'll learn tonight.

 

I agree that the surfaces are not original and that there were at least two toning events on the OP's coin. I was just arguing that the read/yellow next to black can happen naturally and it is not a sign of artificial toning as you seemed to claim in your first post in this thread.

 

Fair enough, at least we have it defined. Unfortunately, I'm down to 6 hours before the alarm rings and that's my limit for the night.

Can you offer examples of coins with similar "one color plus black" toning patterns so we can continue "arguing" tomorrow afternoon? I do not believe I'm wrong with the original coin, considering the propagation patterns - it doesn't follow any rules of "it started here, and progressed this way" - but I'm always willing to reconsider in the face of strong evidence.

 

My belief is the coin was cleaned at one time and has Retoned. And has some sort of environmental damage as well. I'd call it xf details

 

Interesting thread and I am learning .

I may not be able to tell what happened to a coin during it's 175 year life but I still know what I like and I would like to own that coin myself.

 

"Toning like bad wine is used many times to hide a multitude of sins" B.Franklin

 

XF/AU Details

 

Perhaps, but you find me a fully-lustrous uncleaned coin that has a 100% pure as minted surface free of microscopic contamination, die residue, human DNA, etc. Goodbye theory hello real world.

 

Quite right @Mainebill. The black on this coin is CORROSION. Oh, actually late state progressive toning.

...and some one tried to remove a few patches of "the late state progressive toning."

 

Sure, you can say that. Some of the thickest patinas are about 1000nm, but I would estimate the depth of the patina on this coin to be about 200-500nm, based on the color of the lustrous areas. To put this into perspective, a patina of 1000nm is the same thickness as a sliver of wood from a meterstick that is 1/1000th of a millimeter thick. The corrosion is so microscopically thin that it does not have any appreciable effect on the surface of the coin.

 

Here, you have any problems with the theories with these coins that follow the theory perfectly?

http://www.jhonecash.com/research/sunnywood_classification.asp

 

My example is the seated dollar I posted. It is toned nearly black (though it looks a lot brighter in the pictures), and it has red/yellow toning around the devices. This coin has not been cleaned or altered in any way, with the exception of the hole. Here is my theory for why this happens:



A light beam hits the surface of the patina and splits into two, one reflecting off the surface of the patina and one travelling into the patina and eventually reflecting off of the surface of the coin itself. On the lustrous area, the beam is more-fully reflected, so it eventually exits the patina. For these areas, the colors predicted by thin film interference appear.

In the section over where the coin has been worn, the light beam isn't reflected as fully, so a greater percentage of the light beam is absorbed by the coin, and the rest of the light beam is absorbed by the patina. This means that of the white light shone onto the coin, only the part reflected by the patina will be reflected to the viewer. This reflected light is diminished in brightness, which is why the circulated areas of the coin appear grey. If the patina is thin enough, there will be color even over the worn areas. That is why dipped/cleaned coins get colorful as they retone, like this bust half:

To be fair, the patina absorbs the intensity of the light beam over the lustrous area as well. This is why the toning gets darker as the progression furthers with a deepening of the patina.

 

Except that it is very ugly, detracting, and IMHO (?) ruins the eye appeal and much of the value of this PROBLEM coin.

 

Then don't buy it. I am just explaining the physics behind what you are seeing.

 

Did you give up or something? Why are we changing the subject? I am not arguing that toning does not occur in a progressive way. Beautiful progressive rainbow toning is all over the place.

I'm commenting on one of your detractors who thinks most toning is progressive and certain colors can not be found next to each other. If you agree with that (which is not what I read in your posts), I'll be glad to discuss questions about toning with you and others on this thread.

PS Your post#34 is now in my files! Thanks.

 

Perhaps @SuperDave can help you photograph the "golden-grey" coin with a hole so that it actually looks "black." Then it would be easier to see what you are showing us.

 

There is a specific order of colors that have to appear next to each other to be natural. For each increment the patina thickens, the intensities of each of the blue/green/red change to some degree so that their aggregate value produces a specific color. Each specific color has to exist in a specific order with respect to the thickness of the patina, in accordance to the intermediate value theorem.

I am just arguing that there can be a breach in this order when the surface quality is altered.

 

And that is EXACTLY what I've been saying (POST#18) in basic agreement with you!

Rules of nature are broken all the time when man gets involved.