Classical Numismatics Discussion
  Welcome Guest. Please login or register. 10% Off Store-Wide Sale Until 2 April!!! Explore Our Website And Find Joy In The History, Numismatics, Art, Mythology, And Geography Of Coins!!! Expert Authentication - Accurate Descriptions - Reasonable Prices - Coins From Under $10 To Museum Quality Rarities Welcome Guest. Please login or register. 10% Off Store-Wide Sale Until 2 April!!! Explore Our Website And Find Joy In The History, Numismatics, Art, Mythology, And Geography Of Coins!!! Support Our Efforts To Serve The Classical Numismatics Community - Shop At Forum Ancient Coins

New & Reduced


Author Topic: Silver oxidation  (Read 2596 times)

0 Members and 1 Guest are viewing this topic.

Offline Smulan

  • Consul
  • ***
  • Posts: 104
Silver oxidation
« on: March 06, 2019, 05:26:26 am »
I came to think of silver coins and its oxidation process. Wouldn't all the old coins be completely black, if no cleaning has taken place?

Offline mix_val

  • Caesar
  • ****
  • Posts: 1266
Re: Silver oxidation
« Reply #1 on: March 18, 2019, 01:33:05 pm »
Yes but the degree of oxidation depends on how the coin was stored/lost and the chemical environment.   You need a source of H2S to make black Ag2S.
Bob Crutchley
My gallery of the coins of Severus Alexander and his family
https://www.forumancientcoins.com/gallery/index.php?cat=16147

Offline Smulan

  • Consul
  • ***
  • Posts: 104
Re: Silver oxidation
« Reply #2 on: March 19, 2019, 10:38:15 am »
Ok. Is there any natural environment out there that has so little H2S that the sliver still look silver after 2000 years?

Offline mix_val

  • Caesar
  • ****
  • Posts: 1266
Re: Silver oxidation
« Reply #3 on: March 19, 2019, 11:18:20 am »
My guess would be a sealed container in the desert.
Bob Crutchley
My gallery of the coins of Severus Alexander and his family
https://www.forumancientcoins.com/gallery/index.php?cat=16147

Offline Tacitus

  • Caesar
  • ****
  • Posts: 628
Re: Silver oxidation
« Reply #4 on: May 30, 2019, 09:48:34 pm »
I have silver Republican denari that have no blacking at all.
These were found in North Africa.

Offline Joe Sermarini

  • Owner, President
  • FORVM STAFF
  • Caesar
  • *****
  • Posts: 12102
  • All Coins Guaranteed for Eternity.
    • FORVM ANCIENT COINS
Re: Silver oxidation
« Reply #5 on: May 31, 2019, 07:25:07 am »
I have seen coins that I was told were found with the container completely gone, the coins were in a solid black lump, with the coins on the outside destroyed. Broken open, within the lump, some coins at the center were as struck without tarnish. 
Joseph Sermarini
Owner, President
FORVM ANCIENT COINS

Offline djmacdo

  • Tribunus Plebis 2017
  • Procurator Monetae
  • Caesar
  • *****
  • Posts: 4483
  • I love this forum!
Re: Silver oxidation
« Reply #6 on: August 25, 2019, 05:56:07 pm »
The Dekadrachm Hoard from Turkey in the mid-80s had many coins that were barely tarnished--from a sealed container.  Not all corrosion and tarnish on silver can be described as oxidation.

Offline suarez

  • Procurator Monetae
  • Praetorian
  • *****
  • Posts: 51
Re: Silver oxidation
« Reply #7 on: September 01, 2019, 11:33:34 pm »
The Dekadrachm Hoard from Turkey in the mid-80s had many coins that were barely tarnished--from a sealed container.  Not all corrosion and tarnish on silver can be described as oxidation.

With the disclaimer that my knowledge in chemistry is limited it might be worth pointing out that silver doesn't easily oxidize; that is, that it reacts chemically with oxygen. I realize this is academic since informally we equate tarnish with oxidation. Silver tarnish is mostly a product of combining with trace amounts of sulfur. A sealed container should keep silver silvery indefinitely because sulfur atoms are generally too large to penetrate solid materials (unlike oxygen which is fiendishly difficult to make an effective barrier against).

Rasiel

 

All coins are guaranteed for eternity