Awsome Article On Toning Coins And Detecting Them

While purusing ebay, I came across a few toned coins for sale that always demand a premium and it got me thinking if it was possible to artificially tone coins. I figured its a long (years) process of putting a coin in a window (which turned out to be one way)! I came across an excellent article on the history of toning and how to detect artificially toned coins.

http://rg.ancients.info/guide/toning.html

For those who do not have the time to read the whole thing, here are some hi-lights:

Numismatic metals tone in different ways.
toning on silver is most often caused by sulfur

The color of the toning on any coin is a factor of how advanced and thick the film of toning is. Early toning on silver coins is yellow, with the colors progressing to magenta (purplish red) to cyan (greenish blue) to black.

Artificial toning techniques:
such as baking a coin in an oven (alone or in a potato), blasting it with a blow torch, placing it in a covered bowl with crushed match heads (these coins smell!), blowing cigarette or cigar smoke on it, thumbing it with nose grease, or soaking or painting it with bleach, acid, or a sulfur-containing chemical.

How to Tell Artificial Toning on Coins, available for loan from the American Numismatic Association, Campbell says the following are AT tip-offs:

Circular toning spots resulting from the beading of the toning liquid that was used.
Colors that blend together out of sequence. With naturally toned coins, the progression is yellow then magenta (pinkish red) then cyan (blue-green). Toning that appears only on the tops of the lettering and devices and not in the coin's recesses.
Wild "circus" colors -- on 90 percent silver coins, for instance, army green, bright pumpkin orange, and robin-egg blue.

According to PCGS's book Coin Grading and Counterfeit Detection, the following are other indications of artificial toning:

The toning floats on the surface of the coin rather than having depth and being bonded to the metal.
The toning occurs over hairlines or other marks.
The toning exhibits bright "crayon" colors.
The toning has a yellow-brown, smoky appearance, indicating it was caused by cigarette or cigar smoke.
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I am going to take a couple of coins out of my pocket change and take some pictures. I am then going to put them in a potatao and bake them to see what happens. I'll post pictures of the before and after but it will probably be next week (out of potatos at the moment!)