Roerbakmix Posted August 15, 2023 · Member Share Posted August 15, 2023 Part of my hobby is cleaning silver coins. I've posted several threads on CT on my methods. A few weeks ago, I bought this Merovingian denier: This type of encrustation is the most gratifying to remove. I've described it previously as 'flaky metalic horn silver'. My hypothesis is that this type of encrustation occurs in coin hoards. Usually, the metalic deposits are sharply demarcated, on coins of high silver purity. I've employed my usual method of baths in boiling hot sodium thiosulphate solutions, followed by gentle mechanic removal of the deposits. I'm quite happy with how the coin turned out: The coin is slightly darker than it was prior to cleaning, which is a (positive) effect of this restoration method. Basically, silver chloride (AgCl) reacts with sodium thiosulphate (NaS2O3) and forms a thin and stable layer of silverthiosulphate (Ag2S2O3): 2AgCl + Na2S2O3 → Ag2S2O3 + 2NaCl In my experience, this thin layer can fill the thin cleaning scratches, as was the case on the large central cross on the reverse: the scratches on the reverse where recent and shiny, but are now evenly colored with the rest of the coin. I'm however still stuck with identification. Phillipe Schiesser, the leading Merovingian Numismatist (he's auctioning his collection right now at CGB by the way) considers it similar to coin 185 which was part of the Nice-Cimez hoard: ... but I'm not sure I'd agree. I've scrolled through 3 of the 4 volumes of Belfort looking for a positive match, but alas, none. 19 1 4 2 Quote Link to comment Share on other sites More sharing options...
expat Posted August 15, 2023 · Supporter Share Posted August 15, 2023 Good job! Looks much better with an overall darker appearance. Hope you are successful with an attribution eventually. 3 Quote Link to comment Share on other sites More sharing options...
AETHER Posted August 15, 2023 · Member Share Posted August 15, 2023 Incredible results, some of best! 2 Quote Link to comment Share on other sites More sharing options...
CPK Posted August 15, 2023 · Supporter Share Posted August 15, 2023 That turned out beautifully! 1 Quote Link to comment Share on other sites More sharing options...
JeandAcre Posted August 15, 2023 · Member Share Posted August 15, 2023 Bravo! 1 Quote Link to comment Share on other sites More sharing options...
JayAg47 Posted August 15, 2023 · Member Share Posted August 15, 2023 I bet it was satisfying to watch the layers shed off revealing the details! 1 Quote Link to comment Share on other sites More sharing options...
Benefactor Theodosius Posted August 16, 2023 · Benefactor Benefactor Share Posted August 16, 2023 Great result! Your technique has added a valuable tool for horn silver cleaning that I have never seen described by anyone else. John 1 Quote Link to comment Share on other sites More sharing options...
John Conduitt Posted August 16, 2023 · Supporter Share Posted August 16, 2023 17 hours ago, Roerbakmix said: Phillipe Schiesser, the leading Merovingian Numismatist (he's auctioning his collection right now at CGB by the way) considers it similar to coin 185 which was part of the Nice-Cimez hoard It looks almost nothing like 185 to me 😂 What about it tells you it is Merovingian? Quote Link to comment Share on other sites More sharing options...
Roerbakmix Posted August 16, 2023 · Member Author Share Posted August 16, 2023 Thanks all for the positive comments. 14 hours ago, JayAg47 said: I bet it was satisfying to watch the layers shed off revealing the details! It really is! Poking a small metal rod under the deposits, until they crumble, revealing intact and smooth surfaces ... For fun, here is a GIF (5 seconds or so) which I posted previously on Cointalk, showing a timelapse of a severus alexander denarius in the solution. It took about 10 minutes. 2 hours ago, Theodosius said: Great result! Your technique has added a valuable tool for horn silver cleaning that I have never seen described by anyone else. John Thank you @Theodosius. It is however a commonly employed method. Here is an interesting article that compares different cleaning methods: https://www.researchgate.net/publication/276192158_The_Conservation_of_Early_Post-Medieval_Period_Coins_Found_in_Estonia/figures?lo=1 2 hours ago, John Conduitt said: It looks almost nothing like 185 to me 😂 What about it tells you it is Merovingian? Allegedly, the coin was found near Etaples, France (West, coastal region). It's the size and thickness of a sceatta / merovingian denier. I'm very much open for alternative suggestions! It doesn't help that the legend is illegible. 4 Quote Link to comment Share on other sites More sharing options...
Multatuli Posted December 28, 2023 · Member Share Posted December 28, 2023 Excellent results! I don't have much experience cleaning coins. Recently, I acquired a bowl of coins removed from the ground by detectorism, the vast majority of them were medieval Spanish and Portuguese coins. I left and soaked them in olive oil for about 3 weeks, and then I removed the sediments with a toothbrush with firm bristles. The results were kinda satisfactory. The coins are mostly low billon, poor in silver, with a high copper content. Quote Link to comment Share on other sites More sharing options...
Multatuli Posted December 28, 2023 · Member Share Posted December 28, 2023 By the way, here are my only 2 merovingian deniers. The first apparently was struck near of Paris. I don’t have the Belford number. The second was struck in Meldus (Meaux) on the first half of 8th century (700-735). I had classified it as Belford 2869. It’s interesting to see depicted here a swastika, 12 centuries before became a hateful symbol. 2 Quote Link to comment Share on other sites More sharing options...
shanxi Posted December 28, 2023 · Supporter Share Posted December 28, 2023 On 8/15/2023 at 8:07 PM, Roerbakmix said: Basically, silver chloride (AgCl) reacts with sodium thiosulphate (NaS2O3) and forms a thin and stable layer of silverthiosulphate (Ag2S2O3): 2AgCl + Na2S2O3 → Ag2S2O3 + 2NaCl The thiosulphate ions (S2O3)2- and the Ag+ ions form a soluble complex of [Ag(S2O3)2]3-, removing non soluble AgCl. If you get a layer of something afterwards, you didn't wash your coin enough after treatment. 1 Quote Link to comment Share on other sites More sharing options...
Coinmaster Posted January 2 · Member Share Posted January 2 Great and interesting coin! It looks like it's a coin that's inspired by the early Carolingian coins, like this: https://en.numista.com/catalogue/pieces115063.html and this: https://en.numista.com/catalogue/pieces346012.html (and check here for more: https://en.numista.com/catalogue/carolingian_empire-1.html). Possibly it's an 8-century coin. Did you check Simon Coupland? Maybe he encountered this coin type before or knows more about Carolingian-inspired coins. 1 Quote Link to comment Share on other sites More sharing options...
Coinmaster Posted January 2 · Member Share Posted January 2 Here another early example with little cross and dots: https://en.numista.com/catalogue/pieces345339.html And here with a longer and thinner cross like on your coin: https://en.numista.com/catalogue/pieces345772.html. 1 Quote Link to comment Share on other sites More sharing options...
Roerbakmix Posted January 4 · Member Author Share Posted January 4 Thank you @Coinmaster for the suggestion. I have discussed this with Simon Coupland, but alas, he's convinced it's not Carolingian. 2 Quote Link to comment Share on other sites More sharing options...
Coinmaster Posted January 4 · Member Share Posted January 4 Yes, I agree it's not from a Carolingian mint. But I do think it's related (inspired by) and from the same time. So possibly from an unknown (illegal?) mint. It would be nice to see if there exist other examples from the same time that might be related/inspired as well. 1 Quote Link to comment Share on other sites More sharing options...
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