Message:

<p>[QUOTE=&quot;GDJMSP, post: 773251, member: 112&quot;]Info Sponge - </p><p><br /></p><p>Think of it like this.</p><p><br /></p><p>A freshly minted, lustrous coin with normal flow lines has a surface that looks something like this - </p><p>/\/\/\/\/\/\/\</p><p><br /></p><p>A coin that has been over-dipped has a surface that looks like this - </p><p>________________</p><p>- because the acid in the coin dip eats away the top layer or layers of the metal thus making the surface flatter and smoother than it was when it had flow lines.</p><p><br /></p><p>Now, of those two surfaces, assuming they are tone free, ask yourself two questions. First, which one has more surface exposed to the air ?</p><p><br /></p><p>And - of those two surfaces which one is more likely to reflect light in a diffused pattern ?</p><p><br /></p><p>On the first surface /\/\/\/\/\ the light strikes those angled lines from top to bottom. Some of that light is reflected directly back to your eye. But some of it is reflected into one of the adjoining lines and then reflected yet again from that line, and perhaps even reflected off of more than 1 line. And depending on the angle of the light to the surface, and the angle of your eye to the surface, those reflections can be numerous and at all sorts of angles.</p><p><br /></p><p>All of this from untoned surfaces.</p><p><br /></p><p>Now, given that the first illustration /\/\/\/\/\ has more surface exposed to the air, and keep in mind that the surface of these fine flow lines is not flat and smooth either but rather rough with a pebble like effect due to the way that solid metal flows under pressure, it is quite easy to understand why a rough textured surface is more prone to tone, and tone quickly, than a smooth flat surface like this ________ would be. More metal exposed to the air in a small given area means more reaction between the metal and the contaminants in the air. And it is this reaction between the air and the metal that causes toning.</p><p><br /></p><p>Now the illustrations I am using are rather simplied due to the constraints of a keyboard, but they do at aleast convey the meaning and differences between a lustrous surface and an over-dipped surface. Of course the same thing applies to circulated coins as well, for most of their luster is worn away and the surface of the circulated coins becomes flatter and smoother as well.</p><p><br /></p><p>Now, and this what I have tried to explain in other threads on the subject of toning. Yes, toning is due to thin film interference because thin film intereference refracts the light. But then we must also consider the surface that this thin film interference is on, for the angle of the surface that is toned also changes and alters the way the light is reflected.</p><p><br /></p><p>Then, also consider this. That rough, angled surface of a lustrous coin - /\/\/\/\/\/\ - is changed by the toning itself. For the thicker the toning layer becomes, the more those valleys between the lines are filled in. Thus causing that angular surface to gradually become flatter and smoother as the toning progresses. Until it eventually reaches the point that the surface is flat and smooth, much like that of an over-dipped coin. And it is at this point that toning turns dark, brown or even black because those angles are no longer there to refract the light and produce the color that our eyes see. And because the thin film interference isn&#039;t thin any more, it no longer refracts the light either and all of the color is canceled out thus leaving only the dark colors that can still penetrate that layer.</p><p><br /></p><p>Now I&#039;ve said, or at least tried to say,&nbsp; basically the same thing that Jim has said, but in a different way that I for one find easier to understand and visulaize without adding a discussion of physics, photons, absorption and wavelengths. Hopefully.[/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