Cleaning a silver drachm of Orodes I

[robinjojo]

This coin, purchased for $45 online, a mid-grade Parthian drachm, turned out to be a lucky acquisition.  "Lucky" is explained below.

Here's the coin as received yesterday (seller's photos):

Generally speaking I am loathed to any extensive intervention when it comes to coin cleaning, especially ancient coins.  They are coins that have been around for a very long time, stored or deposited in a wide variety of ways.  I feel that when it comes to cleaning, it is important to keep this in mind and not get carried away.

This coin was obviously cleaned in a rudimentary, probably as coins from the hoard that it came from were washed to remove loose dirt.  Fortunately for this coin that was the extent of the initial cleaning process.  I've seen hoard coins that were unfortunately cleaned more extensively, often with a pointed tool to remove deposits, usually leaving significant scratches and harsh tooling marks.  On this coin's obverse there are some scratches in the field in front of the portrait, but they are not too intrusive.

Most of the cleaning was done to the reverse, about a two hour project last night.  I used a combination of naval jelly and thiosulfate solution for the later stages.  Using toothpicks and swabs I applied the naval jelly to the reverse with a swab. I would only leave the naval on the coin for two minutes at the most, gently rubbing the surface with the swab and then rinsing with distilled water.  This step was repeated numerous times given the thickness of the deposits.  Once they were reduced to a satisfactory level, the thiosulfate solution was applied with a swab.  Toothpicks were also used, especially for the recessed areas.  

So, with all that said, here is the coin so far, and I think I'm finished with cleaning it.  There are still deposits, which is perfectly fine with me.  I am not interested in any way to make this coin bright and shiny, a feature of over cleaned coins.

There was some weight loss due to the cleaning.  The coin, as sold, weighed 3.82 grams, but at 3.72 grams it is still in the acceptable weight range.

Luck was on this coin's side: no significant corrosion, just some very light porosity.  Severe corrosion is always a risk with these and other ancient coins.  The color has changed.  Now it is time's turn to tone the coin.

Parthia, Orodes I, AR drachm, Ekbatana, c 90-78 BC.

Sear 7389

3.72 grams

 

Does anyone else have stories cleaning coins? 

Believe me, I've had my fair share of failures, part of my learning curve which in my case is an extremely long curve.

 

Edited September 22 by robinjojo

[Nerosmyfavorite68]

It looks kind of coppery, but that might just be a trick of the light.  The reverse especially turned out a lot better than the before.  I know what you mean by the scratches, and I think we're talking about the same vendor.  The relatively inexpensive Heraclius Hexagrams had terrible scratches.

[Sulla80]

1 hour ago, robinjojo said:

Does anyone else have stories cleaning coins?

That's an amazing transformation of the reverse.  Here are my notes on a "Chemistry Experiment" - nothing as dramatic as your results on this coin:

https://www.sullacoins.com/post/a-chemistry-experiment

The end result of my experiment - improved, a few details more visible.

Edited September 21 by Sulla80

[robinjojo]

37 minutes ago, Nerosmyfavorite68 said:

It looks kind of coppery, but that might just be a trick of the light.  The reverse especially turned out a lot better than the before.  I know what you mean by the scratches, and I think we're talking about the same vendor.  The relatively inexpensive Heraclius Hexagrams had terrible scratches.

 

Yes, very likely the same seller, Zurqieh, who lists lots of these coins on VCoins, along with other hoard coins.  I'd even say he is the main seller of these coins from the UAE.  He must have many sources.

The copper-like color is from the naval jelly.  It has a tendency to tone silver with a yellowish tinge.  That can be eliminated with a liquid silver cleaner, but that would leave the coin looking more over cleaned, I think, so best leave well enough alone in this case.

Edited September 21 by robinjojo

[robinjojo]

That's an amazing transformation of the reverse.  Here are my notes on a "Chemistry Experiment" - nothing as dramatic as your results on this coin:

https://www.sullacoins.com/post/a-chemistry-experiment

The end result of my experiment - improved, a few details more visible.

 

Nice job, Sulla80!  What process did you follow?

Edited September 21 by robinjojo

[Sulla80]

4 hours ago, robinjojo said:

That's an amazing transformation of the reverse.  Here are my notes on a "Chemistry Experiment" - nothing as dramatic as your results on this coin:

https://www.sullacoins.com/post/a-chemistry-experiment

The end result of my experiment - improved, a few details more visible.

 

Nice job, Sulla80!  What process did you follow?

I find thiosulfate works well on horn silver - soak and rub gently - repeat - for heavier deposits a warm solution.  

[robinjojo]

Yes, thiosulfate is very effective.  I really don't like using naval jelly, but with very thick deposits I felt it was a necessary first step.  The thiosulfate solution was useful for the thinned-out deposits.  

I actually don't think the silver oxide deposits were truly horn silver.  My understanding is that horn silver is the result of an reaction of the silver that causes the surface to become black, sometimes waxy.  It is a chemical alteration of the silver that over time grows, often with corrosion on the subsurface.  This coin had deposits that came from external sources.  The rusty deposits suggest that the hoard might have been stored in an iron container.  The granular silver oxide deposits might have come from the decomposition of another objects, probably coins.

I did try thiosulfate initially with little result.  The naval jelly was more effective, but its effectiveness only lasts a minute or two based on my experience.  I would rub the areas with thick deposits with swabs and toothpicks and then risen with distilled water, repeating the process many times.

[Spargrodan]

12 hours ago, robinjojo said:

This coin, purchased for $45 online, a mid-grade Parthian drachm, turned out to be a lucky acquisition.  "Lucky" is explained below.

Here's the coin as received yesterday (seller's photos):

Generally speaking I am loathed to any extensive intervention when it comes to coin cleaning, especially ancient coins.  They are coins that have been around for a very long time, stored or deposited in a wide variety of ways.  I feel that when it comes to cleaning, it is important to keep this in mind and not get carried away.

This coin was obviously cleaned in a rudimentary, probably as coins from the hoard that it came from were washed to remove loose dirt.  Fortunately for this coin that was the extent of the initial cleaning process.  I've seen hoard coins that were unfortunately cleaned more extensively, often with a pointed tool to remove deposits, usually leaving significant scratches and harsh tooling marks.  On this coin's obverse there are some scratches in the field in front of the portrait, but they are not too intrusive.

Most of the cleaning was done to the reverse, about a two hour project last night.  I used a combination of naval jelly and thiosulfate solution for the later stages.  Using toothpicks and swabs I applied the naval jelly to the reverse with a swab. I would only leave the naval on the coin for two minutes at the most, gently rubbing the surface with the swab and then rinsing with distilled water.  This step was repeated numerous times given the thickness of the deposits.  Once they were reduced to a satisfactory level, the thiosulfate solution was applied with a swab.  Toothpicks were also used, especially for the recessed areas.  

So, with all that said, here is the coin so far, and I think I'm finished with cleaning it.  There are still deposits, which is perfectly fine with me.  I am not interested in any way to make this coin bright and shiny, a feature of over cleaned coins.

There was some weight loss due to the cleaning.  The coin, as sold, weighed 3.82 grams, but at 3.72 grams it is still in the acceptable weight range.

Luck was on this coin's side: no significant corrosion, just some very light porosity.  Severe corrosion is always a risk with these and other ancient coins.  The color has changed.  Now it is time's turn to tone the coin.

Parthia, Orodes I, AR drachm, Ekbatana, c 90-78 BC.

Sear 7389

3.72 grams

 

Does anyone else have stories cleaning coins? 

Believe me, I've had my fair share of failures, part of my learning curve which in my case is an extremely long curve.

 

I think it turned out great and I like the patination color that came out in the end!

@Sulla80 good job on the denarius.

I also did clean one of my coin recently with thiosulfate to get rid of hornsilver, I think it turned out good. the patina is a bit more weak now as I cleaned the whole coin to get a more even result but it's still there and with time it will come back so I'm not that concerned.

I wrote about it in another thread here: 

 

Before:

After:

 

 

Edited September 22 by Spargrodan

[Sulla80]

8 hours ago, robinjojo said:

Yes, thiosulfate is very effective.  I really don't like using naval jelly, but with very thick deposits I felt it was a necessary first step.  The thiosulfate solution was useful for the thinned-out deposits.  

I actually don't think the silver oxide deposits were truly horn silver.  My understanding is that horn silver is the result of an reaction of the silver that causes the surface to become black, sometimes waxy.  It is a chemical alteration of the silver that over time grows, often with corrosion on the subsurface.  This coin had deposits that came from external sources.  The rusty deposits suggest that the hoard might have been stored in an iron container.  The granular silver oxide deposits might have come from the decomposition of another objects, probably coins.

I did try thiosulfate initially with little result.  The naval jelly was more effective, but its effectiveness only lasts a minute or two based on my experience.  I would rub the areas with thick deposits with swabs and toothpicks and then risen with distilled water, repeating the process many times.

yes, decomposed coins seem likely to me to be the source of deposits and toothpicks are also very helpful for safely picking.  I haven't used distilled water - just rinse with normal tap water which probably has less consistent results depending on where you live.  All of my attempts have been with fairly ugly coins with low expectations.

[robinjojo]

I've found that naval jelly has virtually no effect on horn silver.  A thiosulfate solution is far more effective for thin or even thick levels of horn silver.  So, as a rule of thumb, if a dark deposit reacts to naval jelly, at least the initial level is likely not horn silver, but keep in mind that horn silver might be beneath it.  That's where thiosulfate comes in. 

But always be aware that corrosion might be beneath that level.  If that becomes apparent, I would stop the cleaning process at that point.  Continuing it would likely expose a raw, pitted surface. The horn silver is part of the coin's original surface, but altered chemically.  Sometimes I think of it as a veneer, albeit a black one.  While it is not as desirable as a nice silvery grey color, for some coins that's the best that can be achieved.