<< <i>1) it "work hardens" the metal more so than other sections of the coin and 2) this extremely work hardened metal has a different metallic structure than the rest of the coin (same composition of course but a different structure on the atomic scale) that makes it more resistant to chemical reactions like toning. Some areas with the stretch mark can tone, it is not untoneable - just more resistant to toning. But from my observation, if you see these tone free areas, you should see the "stretch marks" in the untoned areas. >>
My experience in silversmithing is that work hardened sterling will tone no differently than annealed sterling, on partially finished projects and trimmings left undisturbed 12+ years, including work hardened hammered areas next to fully annealed areas. Surface tension will make a difference in toning - mirror surface from black rouge polishing vrs a surface that is satiny from buffing with tripoli. I don't believe portions of a coin are appreciably different in level of work hardening, except in cases of extremely weak strikes (these areas seem to tone the same as other areas of the coin). My 20+ years of work in a tooling organization also gives the same findings, including material that is intentionally work hardened from shot peening.
Robert Scot: Engraving Liberty - biography of US Mint's first chief engraver
<< <i>1) it "work hardens" the metal more so than other sections of the coin and 2) this extremely work hardened metal has a different metallic structure than the rest of the coin (same composition of course but a different structure on the atomic scale) that makes it more resistant to chemical reactions like toning. Some areas with the stretch mark can tone, it is not untoneable - just more resistant to toning. But from my observation, if you see these tone free areas, you should see the "stretch marks" in the untoned areas. >>
My experience in silversmithing is that work hardened sterling will tone no differently than annealed sterling, on partially finished projects and trimmings left undisturbed 12+ years, including work hardened hammered areas next to fully annealed areas. Surface tension will make a difference in toning - mirror surface from black rouge polishing vrs a surface that is satiny from buffing with tripoli. I don't believe portions of a coin are appreciably different in level of work hardening, except in cases of extremely weak strikes (these areas seem to tone the same as other areas of the coin). My 20+ years of work in a tooling organization also gives the same findings, including material that is intentionally work hardened from shot peening. >>
Thanks for your input Nysoto.
"Work Hardens" was put in parenthesis for a reason. For a reason I wish to clarify.
What I was trying to describe without getting too technical was that I believe the metallic orientation of the crystal structure of the metal orientates itself from the stress, heat and flow of the metal to an orientation that makes the surface there less likely to become dislocated/interact with whatever agent is causing the toning. If you take a crystal, depending on how it is oriented to an agent (like an acid or toning compound), the agent will react at a different rate depending on the orientation of the crystal on the surface. It's hard to explain in layman terms and I was trying to not confuse those that didn't study solid state physics - so I tried to simplify my explanation.
Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues.
But you are correct, it's not just the work hardening that makes that area more toning resistant, it's work hardening that correctly orientates the crystals properly relative to the surface.
That is why the flow must be from a "sharp" angle to the field - like in the star picture I posted above. If there is too much wear (at that crucial zone where the star meets the field) and the angle is more "smoothed out" and not "sharp" enough, the crystals will not "work harden" properly and the flow area will NOT be toning resistant. Just look at the tip of the star at 7 o'clock where there is metal flow but NO toning resistant region!!!!!!!!
In other words, a fresh die will create these toning resistant regions like in the star but a mid-late state die where the junction between the star and the field are not crisp - no toning resistant regions would be created. This is since there would not be enough stress to properly crystallize that region.
A mirrored surface versus a matte one (from striking a coin) will make no difference in toning. Proof coins do not tone any differently than business strikes from my observation. But again, this is from striking. What you describe is from buffing/polishing the surface directly - a totally different process from striking! I don't doubt your observation, but I can't confirm it myself. But I could see how it may. BTW, what "surface tension" are you referring to? That is usually a term used for liquid state. I assumed you were referring instead to surface texture?
You are also correct, the metal on a struck coin has different work hardening and surface crystal orientations. But it's the areas that are "worked hardened" to the correct surface crystal orientations that are able to resist toning! If the metal is work hardened but not correctly oriented, it will not be more resistant by default.
For a second, just look at that star picture I posted. Imagine the flow/stress the metal undergoes in that non-toned region. Then you can get a feel of what the metal is undergoing that enables it to not tone. It's the smoking gun that tells the truth.
<<a fresh die will create these toning resistant regions like in the star but a mid-late state die where the junction between the star and the field are not crisp - no toning resistant regions would be created. This is since there would not be enough stress to properly crystallize that region.>>
Very good point. For those that work with metal , the % of Shear verse fracture of metal struck with sharp dies is a large factor. Sharp dies will produce less shear and more fracture. Fracture being more prone to "toning" due to "cracked" metal service then "sheared" service as on the star at 7:00. exposure.
“A nation can survive its fools, and even the ambitious. But it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and carries his banner openly."
Thank you for your precise and technical presentation on the toning process. I also note that you stated this was not an AT or NT presentation.
However I would like to breach the subject in respect to artificial toning as this is what most of us are concerned about and the cause of many a coin winding up in a body bag after being rejected by PCGS.
In respect to bust half dollars that are at least 170 years old I am always suspicious when I see toned centers and untoned edges around the stars. My gut instinct tells me these 170 old coins tone from the edge towards the center.
When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. The conforms 100% with your proposition of metal stress resistance but only in respect to artificially toned bust halves.
I know some would disagree with my position and at Long Beach I just turned down an otherwise nice R5+ bust half for this very reason. It was presented by a very reputable dealer and perhaps it was natural but still I just can't shake the belief that coins tend to tone from the edge inward.
Thank you BiddlesBank for your input and restating that this thread is not about AT vs NT, just some facts about thin films... aka toning.
I guess it all depends of how the coin was stored. I'm not an expert on how 170 yr old bust halves were stored but the toning you describe does not seem to support the idea of that particular coin being stored in a holder/album that holds the coin firmly in a pre-cut hole around it's edge. In that scenario, it would seem that the cardboard would tone the coin from the edge inward in such a manner that the edge of the coin would have the thicker film - ie more toning.
The closer the coin is to the toning factor, the more it tones in that area. Like in bag toning and the many variations in toning patterns you see there. And the difference in distance to toning depth can be very small! This is why we have such amazing toning patterns such a textile toning! Ever see a canvas bag? The difference in depth is thread deep yet causes great variation in toning depth!
If a coin was NT starting from the center outwards (which is what you seem to be describing), it would make sense that whatever toned that coin started from the center and not the edge. Is there such a holder to account for this sort of NT?? I don't know.
If you can post a picture, I am sure that we could all make a more educated comments on this particular aspect of toning and it's true nature. I am not exactly sure what you are describing since I am not that familiar with toning on early type coins as you described.
Thanks again for your post,
Rob
<< <i><STRONG>Rob
Thank you for your precise and technical presentation on the toning process. I also note that you stated this was not an AT or NT presentation.
However I would like to breach the subject in respect to artificial toning as this is what most of us are concerned about and the cause of many a coin winding up in a body bag after being rejected by PCGS.
In respect to bust half dollars that are at least 170 years old I am always suspicious when I see toned centers and untoned edges around the stars. My gut instinct tells me these 170 old coins tone from the edge towards the center.
When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. The conforms 100% with your proposition of metal stress resistance but only in respect to artificially toned bust halves.
I know some would disagree with my position and at Long Beach I just turned down an otherwise nice R5+ bust half for this very reason. It was presented by a very reputable dealer and perhaps it was natural but still I just can't shake the belief that coins tend to tone from the edge inward.</STRONG> >>
<< <i>When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. >>
One other thing entered my mind, there is a portion of the toning spectrum that is SILVER in color! It is possible that the toning near the stars are indeed MORE toned... but comes out silver in color so as to not appear to be toned at all.
Again, a picture would help here. But this is one other possibility that a naturally toned coin could fit into your description. That's the weird world of toned coins.
You caught me on the way to bed but I snapped these quick photos of an 1820/19. This is what I call reverse toning and tend to stay away from buying coins like this. But I made an exception on this one. This coin has good luster around the edges but only faint luster in the centers.
Now most of the MS bust halves I have handled over the years have darker toning along the rims and lighter toning in the centers and I am not speaking of those that were in albums. So I was wondering if coins toned first along the edges and the build up was greater along the edges for some reason so far unstated. Or perhaps I am missing the color scheme transitions you described.
<< <i>Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues. >>
I do have to disagree with you slightly on this. An acid is no different than any other chemical or toning agent out there. The reason it's called an "acid" is because it has a concentration of H+ ions greater than 1.0x10^-7 moles per liter. When an acid reacts with the atoms on the surface of the coin it doesn't remove the atom and move on to the next one. After the reaction, that H+ ion is used up and can no longer react. If the coin reacts with the acid in a way that creates a solidly binding product, then it will form a protective layer.
The surface of a metal is very prone to reactions. Aluminum metal reacts very rapidly with oxygen and moisture in the air and forms a layer of aluminum oxide on the surface that binds VERY strongly to the aluminum and prevents further corrosion. Iron metal reacts with oxygen in the air forming the familiar iron oxide we know as rust. The iron oxide, however, does not bind very strongly to the iron and spalls away exposing more iron to more oxygen and thus allowing for further corrosion.
You don't need an acid to corrode or react with a metal. In addition, an acid doesn't remove atoms and then continue on ad infinitum. Acids are just like any other chemical reagent out there and once it's been used in a reaction it's done.
I collect the elements on the periodic table, and some coins. I have a complete Roosevelt set, and am putting together a set of coins from 1880.
You are correct. But so was I - at least in my mind.... by "the acid" was meaning all of the acids in the solution and not an individual acid atom.
But reading how it came out, your interpretation of what I wrote fits also!
I messed up, but thanks for catching that. You should go into technical writing, it's 'little' mistakes/ambiguities like I made that make for less than clear writing.
Thanks for clearing that up for everyone!
Rob
<< <i>
<< <i>Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues. >>
I do have to disagree with you slightly on this. An acid is no different than any other chemical or toning agent out there. The reason it's called an "acid" is because it has a concentration of H+ ions greater than 1.0x10^-7 moles per liter. When an acid reacts with the atoms on the surface of the coin it doesn't remove the atom and move on to the next one. After the reaction, that H+ ion is used up and can no longer react. If the coin reacts with the acid in a way that creates a solidly binding product, then it will form a protective layer.
The surface of a metal is very prone to reactions. Aluminum metal reacts very rapidly with oxygen and moisture in the air and forms a layer of aluminum oxide on the surface that binds VERY strongly to the aluminum and prevents further corrosion. Iron metal reacts with oxygen in the air forming the familiar iron oxide we know as rust. The iron oxide, however, does not bind very strongly to the iron and spalls away exposing more iron to more oxygen and thus allowing for further corrosion.
You don't need an acid to corrode or react with a metal. In addition, an acid doesn't remove atoms and then continue on ad infinitum. Acids are just like any other chemical reagent out there and once it's been used in a reaction it's done. >>
This was a great thread, nice to see it again !! For anyone interested in more on this subject, here are a few other threads, and my color chart for toned silver, just to have it all in one place for reference:
Because of their history, Morgan dollars offer more variety in terms of extensive colorful toning than any other series. For anyone who diesn't already know about the TCCS (Toned Coin Collectors Society), there are plenty of discussions there about toned Morgans (or just opportunities to share them with other members).
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Walker Proof Digital Album Fellas, leave the tight pants to the ladies. If I can count the coins in your pockets you better use them to call a tailor. Stay thirsty my friends......
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I happened to see a ASE from the early 1990's with a brilliant and very dramatic rainbow tone. My initial reaction was that there's NO WAY that this coin is naturally toned given that it's such a recent issue. I was then floored when the second photo indicated that it was slabbed and highly rated by a very reputable TPG service.
Maybe i'm pounding this topic into the ground, but I'm preparing to submit some very dramatic rainbows for grading and I know for a FACT that the Morgans in my possession are 100% natural. Now if my Morgans come back 'body bagged' and blazing Moderns are being authenticated then there's something wrong somewhere.....
Perhaps someone can enlighten me as to how a coin from the early 90's could have developed such a dazzling rainbow 'naturally'? Would storing it in an old paper envelope with some ground up match heads nearby be considered a natural process? Or, would just tossing it in an old envelope do the trick?
I don't want to offend anyone and so have not mentioned names or given any specifics... I'm just hoping for some clarification if possible. Is it likely that this was slabbed before it became widely recognized that very well done artifically toned coins were flooding the market?
Happy, humble, honored and proud recipient of the “You Suck” award 10/22/2014
Perhaps i was a bit reckless in my use of the term "rainbow". I don't recall if the coin was a true "rainbow" or not. I was more throwing the term around in describing a brilliantly colorful toned silver coin....with a wide spectrum of color present :-)
A great thread by the way!!! And thanks for all the knowledge being shared here!!!!
Happy, humble, honored and proud recipient of the “You Suck” award 10/22/2014
This is a great old thread... always glad to see it rise to the top again. Along with all the other good, factual information here, derryb's comment is solid fact as well ......
<< <i>toning is corrosion, plain and simple. On a steel penny it's called rust. >>
"Please help us keep these boards professional and informative…. And fun." - DW --------------------------------------------------------------------------------------------------------------------------------------- BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES
Comments
<< <i>1) it "work hardens" the metal more so than other sections of the coin and 2) this extremely work hardened metal has a different metallic structure than the rest of the coin (same composition of course but a different structure on the atomic scale) that makes it more resistant to chemical reactions like toning. Some areas with the stretch mark can tone, it is not untoneable - just more resistant to toning. But from my observation, if you see these tone free areas, you should see the "stretch marks" in the untoned areas. >>
My experience in silversmithing is that work hardened sterling will tone no differently than annealed sterling, on partially finished projects and trimmings left undisturbed 12+ years, including work hardened hammered areas next to fully annealed areas. Surface tension will make a difference in toning - mirror surface from black rouge polishing vrs a surface that is satiny from buffing with tripoli. I don't believe portions of a coin are appreciably different in level of work hardening, except in cases of extremely weak strikes (these areas seem to tone the same as other areas of the coin). My 20+ years of work in a tooling organization also gives the same findings, including material that is intentionally work hardened from shot peening.
<< <i>
<< <i>1) it "work hardens" the metal more so than other sections of the coin and 2) this extremely work hardened metal has a different metallic structure than the rest of the coin (same composition of course but a different structure on the atomic scale) that makes it more resistant to chemical reactions like toning. Some areas with the stretch mark can tone, it is not untoneable - just more resistant to toning. But from my observation, if you see these tone free areas, you should see the "stretch marks" in the untoned areas. >>
My experience in silversmithing is that work hardened sterling will tone no differently than annealed sterling, on partially finished projects and trimmings left undisturbed 12+ years, including work hardened hammered areas next to fully annealed areas. Surface tension will make a difference in toning - mirror surface from black rouge polishing vrs a surface that is satiny from buffing with tripoli. I don't believe portions of a coin are appreciably different in level of work hardening, except in cases of extremely weak strikes (these areas seem to tone the same as other areas of the coin). My 20+ years of work in a tooling organization also gives the same findings, including material that is intentionally work hardened from shot peening. >>
Thanks for your input Nysoto.
"Work Hardens" was put in parenthesis for a reason. For a reason I wish to clarify.
What I was trying to describe without getting too technical was that I believe the metallic orientation of the crystal structure of the metal orientates itself from the stress, heat and flow of the metal to an orientation that makes the surface there less likely to become dislocated/interact with whatever agent is causing the toning. If you take a crystal, depending on how it is oriented to an agent (like an acid or toning compound), the agent will react at a different rate depending on the orientation of the crystal on the surface. It's hard to explain in layman terms and I was trying to not confuse those that didn't study solid state physics - so I tried to simplify my explanation.
Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues.
But you are correct, it's not just the work hardening that makes that area more toning resistant, it's work hardening that correctly orientates the crystals properly relative to the surface.
That is why the flow must be from a "sharp" angle to the field - like in the star picture I posted above. If there is too much wear (at that crucial zone where the star meets the field) and the angle is more "smoothed out" and not "sharp" enough, the crystals will not "work harden" properly and the flow area will NOT be toning resistant. Just look at the tip of the star at 7 o'clock where there is metal flow but NO toning resistant region!!!!!!!!
In other words, a fresh die will create these toning resistant regions like in the star but a mid-late state die where the junction between the star and the field are not crisp - no toning resistant regions would be created. This is since there would not be enough stress to properly crystallize that region.
A mirrored surface versus a matte one (from striking a coin) will make no difference in toning. Proof coins do not tone any differently than business strikes from my observation. But again, this is from striking. What you describe is from buffing/polishing the surface directly - a totally different process from striking! I don't doubt your observation, but I can't confirm it myself. But I could see how it may. BTW, what "surface tension" are you referring to? That is usually a term used for liquid state. I assumed you were referring instead to surface texture?
You are also correct, the metal on a struck coin has different work hardening and surface crystal orientations. But it's the areas that are "worked hardened" to the correct surface crystal orientations that are able to resist toning! If the metal is work hardened but not correctly oriented, it will not be more resistant by default.
For a second, just look at that star picture I posted. Imagine the flow/stress the metal undergoes in that non-toned region. Then you can get a feel of what the metal is undergoing that enables it to not tone. It's the smoking gun that tells the truth.
Thanks for allowing me to further clarify this.
Rob
Very good point. For those that work with metal , the % of Shear verse fracture of metal struck with sharp dies is a large factor. Sharp dies will produce less shear and more fracture. Fracture being more prone to "toning" due to "cracked" metal service then "sheared" service as on the star at 7:00. exposure.
- Marcus Tullius Cicero, 106-43 BC
Thank you for your precise and technical presentation on the toning process. I also note that you stated this was not an AT or NT presentation.
However I would like to breach the subject in respect to artificial toning as this is what most of us are concerned about and the cause of many a coin winding up in a body bag after being rejected by PCGS.
In respect to bust half dollars that are at least 170 years old I am always suspicious when I see toned centers and untoned edges around the stars. My gut instinct tells me these 170 old coins tone from the edge towards the center.
When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. The conforms 100% with your proposition of metal stress resistance but only in respect to artificially toned bust halves.
I know some would disagree with my position and at Long Beach I just turned down an otherwise nice R5+ bust half for this very reason. It was presented by a very reputable dealer and perhaps it was natural but still I just can't shake the belief that coins tend to tone from the edge inward.
I guess it all depends of how the coin was stored. I'm not an expert on how 170 yr old bust halves were stored but the toning you describe does not seem to support the idea of that particular coin being stored in a holder/album that holds the coin firmly in a pre-cut hole around it's edge. In that scenario, it would seem that the cardboard would tone the coin from the edge inward in such a manner that the edge of the coin would have the thicker film - ie more toning.
The closer the coin is to the toning factor, the more it tones in that area. Like in bag toning and the many variations in toning patterns you see there. And the difference in distance to toning depth can be very small! This is why we have such amazing toning patterns such a textile toning! Ever see a canvas bag? The difference in depth is thread deep yet causes great variation in toning depth!
If a coin was NT starting from the center outwards (which is what you seem to be describing), it would make sense that whatever toned that coin started from the center and not the edge. Is there such a holder to account for this sort of NT?? I don't know.
If you can post a picture, I am sure that we could all make a more educated comments on this particular aspect of toning and it's true nature. I am not exactly sure what you are describing since I am not that familiar with toning on early type coins as you described.
Thanks again for your post,
Rob
<< <i><STRONG>Rob
Thank you for your precise and technical presentation on the toning process. I also note that you stated this was not an AT or NT presentation.
However I would like to breach the subject in respect to artificial toning as this is what most of us are concerned about and the cause of many a coin winding up in a body bag after being rejected by PCGS.
In respect to bust half dollars that are at least 170 years old I am always suspicious when I see toned centers and untoned edges around the stars. My gut instinct tells me these 170 old coins tone from the edge towards the center.
When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. The conforms 100% with your proposition of metal stress resistance but only in respect to artificially toned bust halves.
I know some would disagree with my position and at Long Beach I just turned down an otherwise nice R5+ bust half for this very reason. It was presented by a very reputable dealer and perhaps it was natural but still I just can't shake the belief that coins tend to tone from the edge inward.</STRONG> >>
<< <i>When I have seen known artificially toned bust half dollars I have often noticed the centers toned but the area around the stars untoned where most of the luster is present. >>
One other thing entered my mind, there is a portion of the toning spectrum that is SILVER in color! It is possible that the toning near the stars are indeed MORE toned... but comes out silver in color so as to not appear to be toned at all.
Again, a picture would help here. But this is one other possibility that a naturally toned coin could fit into your description. That's the weird world of toned coins.
Rob
You caught me on the way to bed but I snapped these quick photos of an 1820/19. This is what I call reverse toning and tend to stay away from buying coins like this. But I made an exception on this one. This coin has good luster around the edges but only faint luster in the centers.
Now most of the MS bust halves I have handled over the years have darker toning along the rims and lighter toning in the centers and I am not speaking of those that were in albums. So I was wondering if coins toned first along the edges and the build up was greater along the edges for some reason so far unstated. Or perhaps I am missing the color scheme transitions you described.
The toning on that half is not what I was talking about, it appears to be more like areas protected from wear on a slightly circulated coin.
Nice coin BTW. I love coins from this era!
Rob
<< <i>Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues.
>>
I do have to disagree with you slightly on this. An acid is no different than any other chemical or toning agent out there. The reason it's called an "acid" is because it has a concentration of H+ ions greater than 1.0x10^-7 moles per liter. When an acid reacts with the atoms on the surface of the coin it doesn't remove the atom and move on to the next one. After the reaction, that H+ ion is used up and can no longer react. If the coin reacts with the acid in a way that creates a solidly binding product, then it will form a protective layer.
The surface of a metal is very prone to reactions. Aluminum metal reacts very rapidly with oxygen and moisture in the air and forms a layer of aluminum oxide on the surface that binds VERY strongly to the aluminum and prevents further corrosion. Iron metal reacts with oxygen in the air forming the familiar iron oxide we know as rust. The iron oxide, however, does not bind very strongly to the iron and spalls away exposing more iron to more oxygen and thus allowing for further corrosion.
You don't need an acid to corrode or react with a metal. In addition, an acid doesn't remove atoms and then continue on ad infinitum. Acids are just like any other chemical reagent out there and once it's been used in a reaction it's done.
But reading how it came out, your interpretation of what I wrote fits also!
I messed up, but thanks for catching that. You should go into technical writing, it's 'little' mistakes/ambiguities like I made that make for less than clear writing.
Thanks for clearing that up for everyone!
Rob
<< <i>
<< <i>Toning is like puring an acid on a surface in that it reacts by dislocating/removing/reacting with the atoms at the surface at a certain rate. But in an acid, the atoms are removed and the the acid starts to react with the next available atoms. However in toning, instead of removing the atom, it changes it to a new form but keeps it in place. A form that helps to inhibit further reactions, a thin film is formed between the bulk and the reagent. But due to diffusion and reactivity through the new layer, the reaction continues.
>>
I do have to disagree with you slightly on this. An acid is no different than any other chemical or toning agent out there. The reason it's called an "acid" is because it has a concentration of H+ ions greater than 1.0x10^-7 moles per liter. When an acid reacts with the atoms on the surface of the coin it doesn't remove the atom and move on to the next one. After the reaction, that H+ ion is used up and can no longer react. If the coin reacts with the acid in a way that creates a solidly binding product, then it will form a protective layer.
The surface of a metal is very prone to reactions. Aluminum metal reacts very rapidly with oxygen and moisture in the air and forms a layer of aluminum oxide on the surface that binds VERY strongly to the aluminum and prevents further corrosion. Iron metal reacts with oxygen in the air forming the familiar iron oxide we know as rust. The iron oxide, however, does not bind very strongly to the iron and spalls away exposing more iron to more oxygen and thus allowing for further corrosion.
You don't need an acid to corrode or react with a metal. In addition, an acid doesn't remove atoms and then continue on ad infinitum. Acids are just like any other chemical reagent out there and once it's been used in a reaction it's done. >>
for the current rainbow question thread and excellence of this thread.
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Leo
The more qualities observed in a coin, the more desirable that coin becomes!
My Jefferson Nickel Collection
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Towards an understanding of the color progression on toned coins ...
A proposed new classification system for toned coins
The occurrence and appearance of golds and yellows on toned coins
Because of their history, Morgan dollars offer more variety in terms of extensive colorful toning than any other series. For anyone who diesn't already know about the TCCS (Toned Coin Collectors Society), there are plenty of discussions there about toned Morgans (or just opportunities to share them with other members).
TCCS Message Board - "The Rainbow Room"
TCCS Message Board - "Toned Coins"
Sunnywood
Sunnywood's Rainbow-Toned Morgans (Retired)
Sunnywood's Barber Quarters (Retired)
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BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES
Lance.
Fellas, leave the tight pants to the ladies. If I can count the coins in your pockets you better use them to call a tailor. Stay thirsty my friends......
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My initial reaction was that there's NO WAY that this coin is naturally toned given that it's such a recent issue.
I was then floored when the second photo indicated that it was slabbed and highly rated by a very reputable TPG service.
Maybe i'm pounding this topic into the ground, but I'm preparing to submit some very dramatic rainbows for grading and I know for a FACT
that the Morgans in my possession are 100% natural. Now if my Morgans come back 'body bagged' and blazing Moderns are being authenticated then there's something wrong somewhere.....
Perhaps someone can enlighten me as to how a coin from the early 90's could have developed such a dazzling rainbow 'naturally'?
Would storing it in an old paper envelope with some ground up match heads nearby be considered a natural process? Or, would just tossing it in an old envelope do the trick?
I don't want to offend anyone and so have not mentioned names or given any specifics... I'm just hoping for some clarification if possible.
Is it likely that this was slabbed before it became widely recognized that very well done artifically toned coins were flooding the market?
Happy, humble, honored and proud recipient of the “You Suck” award 10/22/2014
ZeroHedge makes debut at White House press corps briefing
I was more throwing the term around in describing a brilliantly colorful toned silver coin....with a wide spectrum of color present :-)
A great thread by the way!!!
And thanks for all the knowledge being shared here!!!!
Happy, humble, honored and proud recipient of the “You Suck” award 10/22/2014
<< <i>toning is corrosion, plain and simple. On a steel penny it's called rust. >>
Cheers, RickO
And this is the other!
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BONGO HURTLES ALONG THE RAIN SODDEN HIGHWAY OF LIFE ON UNDERINFLATED BALD RETREAD TIRES