toned or color charts for silver coins

Mikesp1

Is there such a site.........where there is a description of the different types of color a silver coin can turn into as it ages. If the coin starts out silvery/white .....what are the colors (descriptions/stages) that it may turn? On the other forum, I mentioned I purchased a Merc Dime that looks silvery/white but when you compare it to the rest it is slightly (I mean slightly) darker than the rest to my silvery/white Merc coins. I thought maybe it was the real...real...early stages of russet. Any thoughts?? Thanks from Mike!

Placid

Rob790 posted this in another thread.

"Ok, here is a brief description of the color progression as the film grows thicker:
Yellow - Burgandy - Dark Blue - Lite Blue - Silver - Yellow - Red - Blue - Green - Yellow - Red - Green ....
Now, the colors <Yellow - Red - Green> keep repeating with more and more grey after each repeat until it turns black."

Rob790

Here is a pictire that captures the color progression for thin films:



This is an optical effect called a Black-Light Sandwich, it clearly shows the color progression you would see for any thin film phenomena as the film grows thinker. The center of the pic is where the film is the thinest, and away from the center, the film grows thicker (just ignore the vertical black bar, an unavoidable side effect of the Black-Light Sandwich). In coins, as you can see in the picture, the film grows greyer as it grows thicker- in coins this will eventually lead to black after only a few repetitions of the rainbow. Hard to tell from the pic, but between the first blue zone and the next outer yellow zone is where the silver color will reside- this is easy to see on copper colored coins but will appear as if the blue toning is disappering on silver colored coins as related to an earlier thread. I hope this helps people to understand the color progression in a real way. Also hard to see, but between the red and green bands that repeat are yellow zones.

Mikesp1

Thank you for this info. This will help me understand how the coin turns color with age.

rainbowroosie

Rob 790,
that looks just like the color progression often seen on PCI graded silver eagles slabbed as "white." Members of this board often criticize these coins as being AT....I've never seen a clearer exposition as to why this color scheme is in fact --- NT!!!!!!

Sunnywood

Both AT and NT coins have colors that are optical effects of molecular films on the metal surface. Both AT and NT coins are the result of chemical reactions. Just because a coin exhibits a rainbow effect that is consistent with what one would expect theoretically does not mean it is NT !!!!! It may still be AT !!!!! If you saw my toned Morgans, which have wild variations in color resulting from bag toning, album toning, envelope toning, roll paper toning, end roll toning, and other effects, you would see clearly that no two are alike !! Some do exhibit banded color similar to the theoretical thin film reflection & diffraction patterns, while others are a wild random melange of colors. But they are all NT to the best of my knowledge ... I am very careful about toning. I have also experimented with creating toning on my own just to understand the AT processes better.

Best,
Sunnywood

Rob790

This is the color progression as a function of film thickness. Any gradual slope in thickness across a coin will exhibit this progression, AT or NT- we are talking about film thickness and not how the film has developed. You can think of the thin film as a terrain on top of the coin and depending on the height of the terrain, it will show a corresponding color- for example- a common target toned coin can be visualized as a depression where the high ridges of the depression are at the rim and the center is the valley. If there are any sudden changes in the "terrain", you will see color jumps that are not in sequence to the color chart.

For example, look at this lovely Peace dollar- if you were very small and located at the liberty's eye and looking at the green wedge region, on this 'terrain'- you would be on a flat surface looking at a big V shaped cliff rising from liberty's hair, a rather abrupt change in the terrain and also a jump in the color. This is how I visualize toned coins, kind of strange but useful.