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Kyrene didrachm: before and after horn silver treatment


Jeremy
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I posted this didrachm from Kyrene yesterday in @Alegandron's 'Please Show Your Ancient North African Coins' thread and have since treated the horn silver that darkened the surfaces. There's always some risk in doing this, and I probably wouldn't have, had it been a more expensive coin. I paid a little over $600 for it, which I think is a decent price for the type.

I had been looking for an affordable example of a coin depicting the silphium plant, which was highly coveted in the ancient world and grew in what is now modern day Libya. It was brought to extinction in antiquity, unfortunately.

I thought it would be fun to show a before and after photo. I treated the coin with a 5% solution (by weight) of sodium thiosulfate dissolved in hot distilled water. I soaked it for three or four cycles of about 5 minutes each. At the end of those cycles I was left with a coin that had a dull gray surfaces (free of horn silver), which was easily cleaned up with a paste of sodium bicarbonate (baking soda). There were a few iron oxide deposits along the back of Karneios' head and eye. I applied small drops of mild acid to those spots, loosening the encrustations, which I later gently removed under magnification with a brass scraping tool.

Overall I'm pleased with the result. I think it will look even better as it naturally tones again with age.

Before:

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Treating the iron oxide deposits topically with mild acid:

 spacer.png

Final result:

 spacer.png

The before photo shows what looks like lamination damage at the base/back of the neck, but that isn't present on the coin. It might have been a photography / post editing issue, and probably helped scare away other bidders 🙂

What do you think? Improvement or mistake?

 

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I wouldn't say it's a mistake, because I can see some preferring the cleaned version. That being said, I personally prefer the uncleaned version, since it's more akin to what IMHO an ancient coin should look like and because the contrast makes the details more evident.

Here's my Kyrene silphium.Magas.thumb.jpg.1a4efe84b2a7342af931e8ecd314d60f.jpg

Kyrene, Magas
Ptolemaic governor, c. 300-282/75 BC
AR Didrachm 20mm, 7.30g, 12h
Head of Karneios r. R/ Silphion plant; ZE monogram to upper l., crab to upper r., KY-PA across lower field.
BMC 256; cf. SNG Copenhagen 1243
Ex London Ancient Coins
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32 minutes ago, Jeremy said:

I posted this didrachm from Kyrene yesterday in @Alegandron's 'Please Show Your Ancient North African Coins' thread and have since treated the horn silver that darkened the surfaces. There's always some risk in doing this, and I probably wouldn't have, had it been a more expensive coin. I paid a little over $600 for it, which I think is a decent price for the type.

I had been looking for an affordable example of a coin depicting the silphium plant, which was highly coveted in the ancient world and grew in what is now modern day Libya. It was brought to extinction in antiquity, unfortunately.

I thought it would be fun to show a before and after photo. I treated the coin with a 5% solution (by weight) of sodium thiosulfate dissolved in hot distilled water. I soaked it for three or four cycles of about 5 minutes each. At the end of those cycles I was left with a coin that had a dull gray surfaces (free of horn silver), which was easily cleaned up with a paste of sodium bicarbonate (baking soda). There were a few iron oxide deposits along the back of Karneios' head and eye. I applied small drops of mild acid to those spots, loosening the encrustations, which I later gently removed under magnification with a brass scraping tool.

Overall I'm pleased with the result. I think it will look even better as it naturally tones again with age.

Before:

spacer.png

 

Treating the iron oxide deposits topically with mild acid:

 spacer.png

Final result:

 spacer.png

The before photo shows what looks like lamination damage at the base/back of the neck, but that isn't present on the coin. It might have been a photography / post editing issue, and probably helped scare away other bidders 🙂

What do you think? Improvement or mistake?

 

Nice job... but wow, the Racoon Look was purdy COOL too!

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I like the cleaned version.

I like nice TONING, but I am not a fan of DEPOSITS that were not there when the coin was struck.

Think what the coin looked like when the workers took it off the anvil and dropped it into a leather bag.

I realize it is somewhat a matter of taste with no right or wrong answers.

Wish I could go there to pick a few choice ones out. 😁

John

 

 

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38 minutes ago, Theodosius said:

I like the cleaned version.

I like nice TONING, but I am not a fan of DEPOSITS that were not there when the coin was struck.

Think what the coin looked like when the workers took it off the anvil and dropped it into a leather bag.

I realize it is somewhat a matter of taste with no right or wrong answers.

Wish I could go there to pick a few choice ones out. 😁

John

 

 

Agreed!

I consider removal of horn silver to be an act of conservation. Time will give back the dark toning, but that nasty silver chloride is gone forever 🙂

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Posted (edited)

I actually quite like it too - and I'm sure in time it will look even more lovely as it begins to darken! To be honest, I wouldn't mind too much about having the top coin either but we all have our own opinions and if you like it, that's what matters 🙂 

Edited by AncientNumis
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Looks like it cleaned up well! I think the "after" photo is doing a lot of disservice to your cleaning job due to the harsher lighting that is really highlighting the rough surfaces. If photographed similarly to the original it would probably look much better.

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3 hours ago, Kaleun96 said:

Looks like it cleaned up well! I think the "after" photo is doing a lot of disservice to your cleaning job due to the harsher lighting that is really highlighting the rough surfaces. If photographed similarly to the original it would probably look much better.

Thanks! That's true, the light is much harsher in the after photo. I should probably retake it and diffused light.

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2 hours ago, Jeremy said:

I should probably retake it and diffused light.

Nothing ruins photos quite as surely as harsh light.  From the photos here, I prefer 'before' due to the way the scratches are emphasized on the 'after'.  In hand?  IDK.

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Generally speaking I'm inclined to leave horn silver on a coin, with the caveat that it is not so thick that it obscures major portions of the coin's detail.  Overall I think the OP coin came out okay, but the horn silver seems to have been fairly thin.  Thick horn silver is a real challenge and risky, in my view, since the thickness means that there's a very good chance of corrosion underneath, sometimes pretty bad corrosion.  In the past I found this out the hard way, so even though I am older and not any wiser, but I've learned to go easy when it comes to horn silver.

 

 

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