One member of coin talk told me that "the Romans learned to treat the planchets before striking them into coins. One treatment depleted the copper on the outer planchet leaving an outter shell on the planchet that was more near to pure silver. Coins struck on these planchets had the proper weight & they looked to be 100% silver (on the outside) but the fundamental planchet core included a fair amount of copper. This trickery allowed the ruler of the day to make some serious profit." I heard this story before. There is a "well-known and regarded" coin restorer who changes severely corroded ancients to full silvered condition. His "work" is amazing. He may know the "trick" the roman's used. I should guess it involves a torch as heat is something easily available to the Romans. Anyone here wish to enlighten many of us to the process?
Can't you read? Apparently, the Romans had a method they used. TODAY, I was reminded of hearing something like that two decades ago when I worked for ancient dealers. Perhaps, someone here knows the ancient method. I don't give 2c about anyone posting in MY THREAD who cannot add information about this process. I suggest you push your "ignore" button as IMO, you are the only one making ALLEGATIONS here. Note, I've tagged no one. The person you tagged has me on 'Ignore." IMO, he is not the only person in the world who knows the method used by the Romans. If he does, he's not talking so he'll be as much help around here answering my question as you have been. Now, I have a presentation to a coin club tonight: "Spotting alterations on a coin's surface," so I will be logged off for a few hours. Until then....
Kevin Butcher and Matthew Ponting cover the process in their book The Metallurgy of Roman silver Coinage. Butcher made a video explaining the process too.
Very interesting video...seems like there should be some way to analyze through the coin without being destructive.
THANK YOU! I just got home but the comments lead me to believe it is just what I wanted. IMO, information such as this should be posted someplace at the begining of the ancient forum board (forgive me if it is there already) along with weights of each denomination, etc. Perhaps even the symbols of the city states. We all have books for this but it would help the new ancient collectors. EDIT: Great Video. Need to get the book for my library.
Specific gravity is the only non-destructive test I know of as all the others (without shaving or drilling damage) only read to a thin depth of the surface. Trouble w/SG testing is ancients often have fissures that trap air and screw up the readings. I suppose using a vacuum chamber of some kind or forcing the water into the coin by soaking it under pressure would make the test more accurate. Wonder what that "rig" would cost. A month ago I tried to take specific gravity readings from a group of sea salvage 8 Reales with no luck. I could see bubbles forming on the coins surface shortly after submersion. The SG readings varied by .7 which was of no use to me at all. I assure you it was not funny at the time.
I have a page on metallurgy of Constantinian "bronzes" which also talks about some of the silvering processes with links to books and articles that go into more depth http://www.constantinethegreatcoins.com/metallurgy/
