Bronze disease

I ORIGINALLY POSTED: "The crystallization on this coin is unusual. Perhaps some of the experts here can authenticate it BEFORE the OP changes its appearance."

Apparently you have not read my various posts concerning how coins are authenticated. No opinion is valid until the FINAL opinion is rendered. Authenticators (at least me) frequently change their mind back and forth (good/bad) when examining a coin due to further tests/research! I just authenticated a typical coin which provides an excellent example: 1804-Mo,TH 8 Rls.

1. Eye: Nice XF/AU coin but cleaned. GENUINE
2. Microscope 10X: Unusual surface, due to cleaning? Possible fake?
3. WEIGHT: OK GENUINE
4. Microscope 20X: Lacks Mint quality. Possible fake?
5. EXAMINE EDGE: 100% counterfeit - no need for specific gravity test (thank goodness as these are tedious).

 

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I ORIGINALLY POSTED: "The crystallization on this coin is unusual. Perhaps some of the experts here can authenticate it BEFORE the OP changes its appearance."

Apparently you have not read my various posts concerning how coins are authenticated. No opinion is valid until the FINAL opinion is rendered. Authenticators (at least me) frequently change their mind back and forth (good/bad) when examining a coin due to further tests/research! I just authenticated a typical coin which provides an excellent example: 1804-Mo,TH 8 Rls.

1. Eye: Nice XF/AU coin but cleaned. GENUINE
2. Microscope 10X: Unusual surface, due to cleaning? Possible fake?
3. WEIGHT: OK GENUINE
4. Microscope 20X: Lacks Mint quality. Possible fake?
5. EXAMINE EDGE: 100% counterfeit - no need for specific gravity test (thank goodness as these are tedious).

I said your coin was unusual and BEFORE you change its appearance you should make sure. What you have posted (another image) probably proves that this form of crystallization see on your coin may be more common than either Mr. Sear or myself believe. Hopefully, your example is not being sold by that same dealer!

Therefore, evidence points to the possibility/probability that environmental damage or chemical cleaning has caused this surface. I'll have more to say to the rest of your post but again - the black rectangle is back and I cannot be sure this will post in a timely manner.

I think it works as soon as someone else posts here.

 

EDIT:
I found a third coin with the same surface, I guess not that extremely rare anymore.



It is clear chemicals were used to remove the patina/clean causing surface etching.

So far that MAY be the case.

Now, I have a request for you. It appears to me that whenever a member in the ancient forum posts a coin they also post the attribution. That would be very helpful so folks who do not collect ancients can search for comparison images on the net.

Thanks in advance.

PS I still have not seen an image of the EDGE of your coin.

 

Maybe this is just a personal niggle, but IMHO it would probably be more accurate to say:

"It is clear chemicals were used to remove the patina/clean revealing surface etching"

(Unless of course the item is some kind of clever pressure cast - I have no comment on that)

More generally:

At a practical level - very pure silver pieces can become very fragile if buried in a saline environment - due to what certainly appears to be internal crystallisation. This can often be reversed by moderate heat - a bread oven - for a period of hours. Don't ask me how it works, I do not know. Others have told me this cannot be true, but they are wrong, as I did it, quite a lot.

Regarding copper alloys. Crystallisation does not seem to me to cause fragility in copper alloy coins, so I never tried to anneal them. Those experienced in conservation work tell me - if removing bends from damaged copper alloy items – the copper alloy must first be heated to a very high (cherry red) temperature.

I assume that is to anneal it? But what do I know? Only this - that is what practical people said they found worked.

The enlightenment happened when people put aside theories to trust what they saw for themselves. Often enough I fear, due to modern education, we increasingly forgot that fact.

Rob T

 

EWC3, posted: "It is clear chemicals were used to remove the patina/clean revealing surface etching"

Actually, I don't believe this. Of course this coin was cleaned. Most ancients have been and they don't look like this. While "selective etching" does occur to metal made of different alloys in which case a pattern will remain on the metal, that is not the case here. The ENTIRE COIN is crystallized throughout

"...(Unless of course the item is some kind of clever pressure cast - I have no comment on that."

Most here believe the coin is 100% genuine and one has not made up his mind.

EWC3, posted: "The enlightenment happened when people put aside theories to trust what they saw for themselves. Often enough I fear, due to modern education, we increasingly forgot that fact."

Well said!

Perhaps some year the OP will post several images of the edge of this gem. I expect to see either crystals or filing.

 

This is another coin with the same crystallized surface. Since the consensus is that these coins are genuine then the planchets for these coins were CAST.

 

Hello Insider

Thanks for the thoughts

We seem to be at cross purposes here. I suspect also that The ENTIRE COIN is crystallized throughout. But cleaning coins only requires dilute acids, and they do not etch metal. What they do do is remove encrustations and reveal all sorts of residual surfaces underneath. The soil is not a machine turning out coins with lovely patinas, or indeed any other consistent result. The surface patterns I see on these coins seem to me be be random acts of corrosion in the ground, merely revealed by chemical cleaning

Nope -at least two. I see nothing wrong with the coins from the scans, its my own obstinate rule - I just never give a final opinion from a scan

Excellent! Well met.

Rob T

 

Sorry, but I trust David Sear on this one

How do you know the person who cleaned this coin used "dilute acid". Who knows that person was an idiot, did not know what he was doing and put it in concentrated strong acid. Or who knows that person wanted to sell his coins quick and put it in concentrated strong acid so the coin would be quicker cleaned?

I have seen nitric acid with copper many times. It will look very shiny and an unbelievable unregular surface, just like the coin above. As I said, you don't know the history of this coin nor the way it is cleaned. If you don't have chemical knowledge then don't rule out that no chemicals have caused this, it will always stay a possibility.

Besides that, what is your definition of "dilute acid"? If you mean it is low concentrated then "diluted" is a very wrong word to use in Chemistry. For example Hydrochloric acid is a GAS in water and never reaches more then 37% concentration, so it is diluted already. However it is still a strong acid and highly concentrated. If I put 1L concentrated acid in 10ml water it is diluted but still very high concentrated.

For your definition you use the word "low concentrated acid", actually even that is wrong because "low" is a matter of personal opinion, that's why numbers are always necessary, either percentages or ratios.

This is extremely wrong, no internal crystallization takes place if you leave silver in saline solution. Actually silver chloride crystals are formed, the silver itself does NOT crystallize in saline environments nor is it INTERNAL. It are just silver chloride crystals that form and yes if you heat it in a bread oven then it will decompose. If you want to remove INTERNAL crystallization of the METAL silver then you need to heat till the melting point of silver. Chemistry

 

Yes, of course. That's coin-making 101. Should not surprise anyone.

 

Just as I predicted. (And please do try to reply more carefully - that is to say - to what I actually wrote)

In my day, a scientist tested theories against fact, not fact against theories.

Anyhow, I was warned about this sort of thing on joining the group, and I guess insider feels similarly? Am too busy just now - but maybe down the line I might try a thread on matters to do with intellectual decline. Do people objectively see it going on? If so - what to blame? Professionalisation of culture? Social media?

Rob T

 

EWC3, posted: "We seem to be at cross purposes here. I suspect also that The ENTIRE COIN is crystallized throughout. But cleaning coins only requires dilute acids, and they do not etch metal."

We'll disagree here as it depends on the particular acid and the composition of the metal and how it was formed.

What they do do is remove encrustations and reveal all sorts of residual surfaces underneath. The soil is not a machine turning out coins with lovely patinas, or indeed any other consistent result. The surface patterns I see on these coins seem to me be be random acts of corrosion in the ground, merely revealed by chemical cleaning.

We'll disagree again. This is a typical crystallization pattern seen on many casts. They are not usually present on corroded coins.

Pavlos, posted: "Sorry, but I trust David Sear on this one."

Don't be sorry, WE ALL trust Mr. Sear. He makes a living with ancients.

"How do you know the person who cleaned this coin used "dilute acid". Who knows that person was an idiot, did not know what he was doing and put it in concentrated strong acid. Or who knows that person wanted to sell his coins quick and put it in concentrated strong acid so the coin would be quicker cleaned?"

None of us was there. We know NOTHING about the coin's history EXCEPT that you bought it an posted it.

"I have seen nitric acid with copper many times. It will look very shiny and an unbelievable unregular surface, just like the coin above. As I said, you don't know the history of this coin nor the way it is cleaned. If you don't have chemical knowledge then don't rule out that no chemicals have caused this, it will always stay a possibility."

That's for sure and the various possibilities make things interesting!

"Besides that, what is your definition of "dilute acid"? If you mean it is low concentrated then "diluted" is a very wrong word to use in Chemistry. For example Hydrochloric acid is a GAS in water and never reaches more then 37% concentration, so it is diluted already. However it is still a strong acid and highly concentrated. If I put 1L concentrated acid in 10ml water it is diluted but still very high concentrated. For your definition you use the word "low concentrated acid", actually even that is wrong because "low" is a matter of personal opinion, that's why numbers are always necessary, either percentages or ratios."

You are getting way off the subject with the acid. I've played with concentrated Sulfuric, Nitric, and Hydrochloric acids and metal in my fathers business since I was a teenager. I'm probably very fortunate to have both eyes and fingers. Nevertheless, I flunked college chemistry the first time I took it and I still don't know much about it - acid into water right?

Anyway, the important thing is I've examined a lot of etched metal under a stereomicroscope and the chemistry/concentrations you bring up is of no use to me. Just about every ancient coin has been cleaned with something. It is funny to me that this crystal patter is uncommon. The dealer has two of them and you posted an image of another. Perhaps the dealer who sold you the coin needs to refine the way he treats them before the sale. Perhaps his supplier is the one destroying coins.

Let's get back on topic. SHOW US THE EDGE! Please.

"This is extremely wrong, no internal crystallization takes place if you leave silver in saline solution. Actually silver chloride crystals are formed, the silver itself does NOT crystallize in saline environments nor is it INTERNAL. It are just silver chloride crystals that form and yes if you heat it in a bread oven then it will decompose. If you want to remove INTERNAL crystallization of the METAL silver then you need to heat till the melting point of silver. Chemistry"

More unrelated "chatter." Your coin is mostly COPPER! Perhaps we can confine the discussion to that metal and its alloys. Silver was originally brought into the discussion because someone didn't think the patterns on metal could be called crystals although that's what they are commonly referred to in the literature.

Ken Dorney, posted: "Yes, of course. That's [Ancient] coin-making 101. Should not surprise anyone."

It shouldn't but there are a lot of less knowledgeable folks than you who may be reading this. Here is the thing. Why don't the millions of ancients struck on cast planchets made of bronze look like the OP's coin and the other coin the dealer has? I'll bet most were cleaned in the past.

While I respect the opinion of experts, I don't take their word as fact until all my questions are answered and I become convinced. In my experience, too many of them have turned out to be wrong.

For now, I'm just taking all sides of the discussion to learn as much as I can about a bronze surface that is very unusual to me. So far, the consensus seems to be that the OP's coin is genuine. It is not rare or unusual. It has suffered some type of cleaning that has modified its surface.

I've posted it on another forum and I'm hoping the OP will image a few parts of its edge - if only in the interest of educating me. Goodnight all.

 

Thanks for the thoughts insider

Afraid that was not at all clear to me. Look at the left side of the obverse. A curve of deeper pitting. My money is on that being because there was a second coin stacked on it in the ground, and the pitting it got in the ground was slightly accelerated along the join by that circumstance. I have seen that many more times than I can count.

But I already answered that – when I said

EWC3: The soil is not a machine turning out coins with lovely patinas, or indeed any other consistent result.

If so I am giving my opinion that that consensus is wrong – but I am not surprised to hear it.

Actually, that is my main point. Your ordinary collector is very prone to say dismissively – “it was damaged by cleaning”. And they are most times wrong – the damage was most times already there – cleaning just revealed it

I would be very surprised to hear the initial coin was anything but a genuine coin, damaged by corrosion in the ground.

A side issue maybe, but errors about these sort of matters are widespread. Here is a link to a paper I put in NC. It was put to correct a number of errors made by a member of BM staff, one of which was a serious failure to understand sub-soil corrosion in a particular case……………

https://www.academia.edu/4645738/Late_Indian_Punchmarked_Coins_in_the_Mir_Zakah_II_Hoard

Anyhow, its great to debate with a cautious guy who puts his faith in logic and observation,

Regards

Rob T

 

Sorry, cannot open it. Off to the Lakeland, FL Coin Show.

 

Don't get the coins wet