Message:

<p>[QUOTE=&quot;TypeCoin971793, post: 2427500, member: 78244&quot;]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:</p><p><br /></p><p>[ATTACH=full]503940[/ATTACH] </p><p><br /></p><p>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.</p><p><br /></p><p>In the section over where the coin has been worn, the light beam isn&#039;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:[ATTACH=full]503959[/ATTACH]</p><p><br /></p><p>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.[/QUOTE]</p><p><br /></p>

Your name or email address:

Do you already have an account?

• No, create an account now.
• Yes, my password is:
• Forgot your password?

Stay logged in