Return to carbon spots...

[Hoot]

Some coins come well toned with what appear to be "old" carbon spots.

 

(1) Have such spots already impaired the surface of the coin and what are the consequences of removing them?

 

(2) What do these spots do to the surfaces of coins over time?

 

(3) What are the consequences of carbon spots on different metallic compositions?

 

(4) Can these spots be removed without affecting the surface in general, thus preserving desirable toning?

 

Thanks fo the information.

 

Hoot

[NCSSilliman-migration]

There isn't one simple answer for spots on coins.

 

Some spots come right off the coin leaving not trace that there was anything there before. These spots are usually foreign material that has attached to the coin and may have caused some discoloration underneath and around it. Other spots are imbedded in and grow out of the surface of the coin. These spots will also discolor the metal around them. They can sometimes be removed along with the discoloration, but sometimes slight discoloration remains where the spot was. This is especially true of silver coins.

 

On copper coins, the dark spots, commonly refered to as carbon spots usually leave discoloration or a shadow where the spot was. If not removed, spots on copper can develop into corrosion, changing color, size and shape.

 

On gold coins, we often see copper spots. These can almost always be removed with little or no trace that there were there before.

 

In many cases, at least on silver, gold and nickel spots can be removed with out affecting toning. It depends largely on the amount of toning, and the size, severity and location of the spot. Spots on copper can usually be reduced in size and severity, especially when becoming corrosive, but more often than not a shadow of the spot will remain.

 

Regards,

 

[Beijim]

Great question and information here - thank you!

 

Beijim