Bronze Disease/Verdigris On Silver Denarius?

To participate in the forum you must log in or register.

Author	Replies: 3 / Views: 3,204
Kefiroth Pillar of the Community United States 1431 Posts	Posted 02/23/2018 4:56 pm Hello all, Lately, I had noticed while examining this denarius of Hadrian under a bright white LED light, some pale-greenish residue on the reverse surface and as well as inside a shallow rim crack. Not sure if this is just some inert residue that took on a greenish color, or something more insidious. Since this is not one of the later, heavily debased issues, I would think bronze disease would be out of the question, but as there is still some copper content present, I'd just want to be sure. This coin has been stored inside a PVC-free cardboard 2x2. For what it's worth, a gentle rub with the tip of a toothpick seemed to pick it right up, though I was unable to get the stuff inside the rim. full coin: inside the rim crack: reverse surfaces: Thanks! Edited by Kefiroth 02/23/2018 5:25 pm Report this Post to the Staff

sel_69l Bedrock of the Community Australia 21788 Posts	Posted 02/23/2018 5:48 pm I would do an intensive Google search, looking at the various methods of the passivation of verdigris. In the case of a Hadrian denarius, the alloy is not orichalcum (a zinc-copper brass, found in dupondii and sestertii) or bronze (tin-copper bronze). The silver alloy in the case of this particular Hadrian denarius has copper, but has more than 50% silver. The high proportion of silver in the alloy has greatly suppressed the formation of verdigris, but not arrested it. Give consideration as to which approach to the treatment of verdigris, may best suit the treatment of this coin. I think it is imperative that something must be done. Picking at it with a toothpick would seen to be a good first step. The silver alloy would be very much harder than the wood of a toothpick. Edited by sel_69l 02/23/2018 6:07 pm Report this Post to the Staff
echizento Moderator United States 23731 Posts	Posted 02/23/2018 5:52 pm It might be some transfer verdigris from the coin being buried with bronze coins. Or the coin could be a fouree, but it doesn't look like one. Also these coins were not 100% silver and it's possible that due to moisture what base metal that was there is leaching out. Report this Post to the Staff
sel_69l Bedrock of the Community Australia 21788 Posts	Posted 02/23/2018 6:05 pm Typically, the purity of the silver in Hadrian denarii is around 85%, but the fact that this particular coin presents with verdigris, suggests to me that the silver content may be (I guess) around 70-75%. The rest of the coin still looks quite silvery, unlike the tendency to blackening with billon (less than 50% silver), coins. Verdicare may help remove the light surface greenish tinge, but probably won't help in the small green pitted areas. I agree with what echizento has said. Report this Post to the Staff
	Replies: 3 / Views: 3,204

To participate in the forum you must log in or register.

All Forums Category: World Coins and Currency Forums Forum: Ancient, Greek, Roman, and Medieval Coins

The First Dollar, your premier source for bullion and rare coins. See our bullion list on the site and the coin inventory on ebay.

Silver Gold Bull US is the United States leading bullion dealer. We deliver gold coins, gold bars, silver coins, silver bars and precious metals to your door. Order today!

View Last 100 New Topics

View Last 100 Active Topics

Disclaimer: While a tremendous amount of effort goes into ensuring the accuracy of the information contained in this site, Coin Community assumes no liability for errors. Copyright 2005 - 2026 Coin Community Family- all rights reserved worldwide. Use of any images or content on this website without prior written permission of Coin Community or the original lender is strictly prohibited.
Contact Us | Advertise Here | Privacy Policy / Terms of Use

Coin Community Forum

It took 0.23 seconds to rattle this change.