I was wondering if I could get some ideas on the differences between Patina and Toning when discussing ancient bronze coins... how it develops, etc. -would ALL bronze/copper coins 1800+ years old develop a patina? Or does this only develop when they come in contact with soil, water and/or other natural elements over the centuries? -if a coin was found after 1800 hundred years in a dry place - like say between two dry bricks would it not look mint state when found (after a quick wipe) or would a patina be present? -I assume toning is a reaction to the particles/gasses in the air? Is it the start of the patination process? Cabinet toning - I assume is from the off gasses from the cabinet's wood. Using my Probus coin below as an example ... do you think this has been stripped of patina at an earlier date and only started toning since then?... or is it possible this is a coin in its original state that was found as is.. only toning due to age/air/gasses? Obviously no one knows for this example .. but do we assume ALL coins in the state below have been stripped of patina?? Please add any nicely toned bronze coins.. and your opinion on this subject is very welcome!
To my knowledge, the oldest un-patinated bronze coins are from the 1600s or early 1700s. Silver does tarnish more easily, but copper is quite reactive to organics. To go more than a few centuries without developing a patina, a copper coin would proably have to be conditions like a modern slab, touching inert material and surrounded by inert nitrogen. The difference in silvered coins is that the thin silver wash still protects the coin from the environment. (Thats a really nice Probus by the way!)
I doubt it was stripped. I believe your coin was given a silver wash in antiquity and that silver wash is now toning. Chemically, patination and toning are distinct phenomenons.
To elaborate, antoniniani of Probus, like yours - beautiful coin, BTW - were mostly bronze but were coated with a thin silver wash through a process that we don't yet fully understand. So I'm guessing your coin has never been stripped, because any method of stripping a coin that I know of would also remove the silver wash. Because your coin has retained its silver wash, the surface has toned, meaning that it has reacted with some of the trace chemicals in its environment. If you were to strip off this silver wash (don't you DARE!) and expose the bronze surface underneath, the coin would slowly develop a patina.
Patina has become a rather fluid word in recent decades and in common English has changed to a synonym for aged, old, tarnished, etc. For our purposes it usually refers to the tarnish and or encrustations on a base metal coin. As such, both words 'patina' and 'toning' really mean the same thing. In more detailed usage though, toning occurs before patina. Both can be artificially induced. As for your coin, I dont think it was cleaned much and likely came out of the ground looking very similar to what it does now. If one does a little searching they can find lots of examples of silver coins coming out of the ground shiny and brilliant. It just entirely depends on the specific burial circumstances.
