Featured Restoring a hammered silver medieval penny

Discussion in 'Ancient Coins' started by Roerbakmix, Feb 20, 2020.

  1. Roerbakmix

    Roerbakmix Well-Known Member

    So, last week I bought this silver medieval penny, which was identified by the seller as "an English penny with a king". It was @AnYangMan who identified this coin as a silver penny of
    Diederik van der Ahr, Bishop of Utrecht (the Netherlands) in 1197–1212.

    The coin had some issues, but the price was right (€32, including postage), and as I was looking for medieval coinage of the Netherlands (which is where I live), I decided to buy it regardless. Also, as some of you may know, I enjoy restoring silver coins.

    So, the coin:
    imgonline-com-ua-twotoone-n6Z1Sax3bgfNq.jpg
    This is a difficult combination of a nice patina (silver sulfide; Ag2S), with some copper oxides (the dark green parts) and beneath that, iron oxide. Also, there are some spots with metal-like horn silver. Care should be taken not to remove the patina.
    upload_2020-2-20_21-23-9.png
    Red arrows: horn silver >> dissolves in sodiumthiosulphate
    Green arrows: copper oxides >> dissolves in synthetic citric acid
    Dark-red arrows: iron oxides >>dissolves in synthetic citric acid
    Overall grey appearance: silver sulfide >> does not dissolve in sodium thiosulphate or citric acid.

    I proceeded as following:
    1) first, the coin was shortly (60 sec) submerged in a hot solution of sodium thiosulphate in distilled water. This dissolved the spots of horn silver
    2) the coin was submerged in a hot solution of distilled water and citric acid
    3) then, with a bamboo skewer, I scraped over the deposits, without applying too much pressure. This step serves to create small cracks in the deposits, which speeds up the chemical process
    4) step 2 and 3 where repeated multiple times.
    5) the silver beneath the deposits was shinier than the rest of the coin. Sodium thiosulphate was used to darken these spots.

    So, this was the final result after ~60 mins:
    upload_2020-2-20_21-30-36.png
    COUNT OF HOLLAND, Diederik van der Ahr. Denomination: AR penny, minted: Utrecht, the Netherlands; 1197-1212
    Obv: TЄODЄ - RICVS, facing bust of Dirk van Aare in episcopal regalia; crozier to left.
    Rev: cross pattée; in opposite quarters, pellet-in-annulet and trident with annulet ends
    Weight: 0.58g; Ø:14mm. Catalogue: Van der Chijs VI, 2 ,de Mey 159, de Wit Collection 878. Provenance: Ex. private collection; acq.: 02-2020
    An interesting and scarce type.

    Hope you enjoyed :)
     
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  3. John Anthony

    John Anthony Ultracrepidarian Supporter

    That's a tremendous improvement! I wouldn't go any further though, that coin looks perfectly great as it is.
     
  4. Kentucky

    Kentucky Supporter! Supporter

    I'm impressed!
     
  5. dougsmit

    dougsmit Member Supporter

    What is a reasonable translation of TEO? It would seem a bit close to 'God' for use by a cleric but I could see 'His Holiness'.
     
  6. Archeocultura

    Archeocultura Well-Known Member

    ' theon' means 'people' and 'ricus' is rich, and thus mighty man. You are no doubt familiar with Theoderic who invaded Italy. Since then we find this name as a professional name ' ruler over people' in English as Derrick, in French as Thierry, in German as Dietrich and in Dutch as my own surname Diederik.
    Nice coin btw and good cleaning job!

    Frans
     
  7. FitzNigel

    FitzNigel Medievalist Supporter

    Awesome cleaning job! Nice looking coin now
     
    Roerbakmix likes this.
  8. Suarez

    Suarez Well-Known Member

    Nice job on that coin. I admire those who have this combination of art and skill!

    Rasiel
     
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  9. Marsyas Mike

    Marsyas Mike Well-Known Member

    Very impressive work. Interesting coin too.
     
    Roerbakmix likes this.
  10. Roerbakmix

    Roerbakmix Well-Known Member

    Thanks all for the kind comments. @Archeocultura: I didn't know about that. Interesting! I know a few 'Dirks', this can lead to some interesting conversations :)
     
  11. TIF

    TIF Always learning. Supporter

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  12. Orielensis

    Orielensis Well-Known Member

    Well done! Your impressive cleaning skills definitely improved the looks of this scarce and interesting penny.
     
    coinsareus10 and Roerbakmix like this.
  13. +VGO.DVCKS

    +VGO.DVCKS New Member

    This is truly stunning. I've never seen a cleaned coin before that didn't look, well, cleaned. An amazing combination of expertise and sheer skill. Your accomplishment is every bit as impressive as the end result. For now, though, I'm happy to gloss over the technical details and write it off to alchemy.
     
    Stevearino and Roerbakmix like this.
  14. robinjojo

    robinjojo Well-Known Member

    Nice preservation. The coin retains enough of the original patina. The shiny spots will tone down over time - they might darken rather quickly if the coin is left out to tone.

    Sometimes removing horn silver can be risky, as sometimes the deposit has corrosion underneath it. Also, the thickness of the deposit is a factor as well.
     
    Roerbakmix likes this.
  15. thejewk

    thejewk Well-Known Member

    Nice job.
     
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  16. Roerbakmix

    Roerbakmix Well-Known Member

    Thanks all for the kind words. I've been away from CT for a while because of the COVID crisis. As a resident Internal Medicine in an academic hospital in the Netherland, things are changing everyday, leaving little time for hobbies (or even for my PhD).
    Logging in and seeing many alerts and this post featured gave me a positive morning :)
     
  17. Alegandron

    Alegandron "ΤΩΙ ΚΡΑΤΙΣΤΩΙ..." ΜΕΓΑΣ ΑΛΕΞΑΝΔΡΟΣ, June 323 BCE Supporter

    Be safe! And thank you for your work. I know it is your job, but taking an everyday risk of exposure on the front-line must be harrowing.
    Best,
    Brian
     
    Kentucky and +VGO.DVCKS like this.
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