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Technology The technology used to produce fakes.

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Old Feb 16, 2004, 10:54 AM   #1
esnible
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Falsifying the appearance of ancient silver 2

We have previously discussed my Mesembria diobol. I have taken a new photo of it. The photo was too large for the gallery here, so you may see it on my web site:
http://www.snible.org/coins/surfaces...ria_cement.jpg
http://www.snible.org/coins/mesembria_fake.html

This coin has been outed as Black Sea Fake by Robert Kokotailo and Wayne Sayles. (See earlier thread.)

The patina on the obverse of the coin is very deceptive. The patina on the reverse of this coin gives it away as a fake. Perhaps the patina on this coin will give us valuable clues towards methods of achieving false patinas in modern Bulgarian fakes.

Peter Northrup has offered to analyze the patina desctructively for $500. I'd be willing to pay 1/10 of that. Dr. Northrup is out of my price range.

Has anyone seen coins with similar patina? I would appreciate photos or scans for comparison.
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Old Feb 17, 2004, 03:09 PM   #2
wgsant
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Ed;

The coin is a fake, no doubt in my mind about that, but I don't follow your argument about the patina on the reverse. Why is it that these "bumps" can't appear naturally on a coin?
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Old Feb 17, 2004, 07:07 PM   #3
esnible
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Under the binocular microscope the bumps don't look like part of the coin. Neither do they look like a patina. They look spattered or spackled onto the coin.

If I can't get a good photograph I will send you the coin. You can tell me if you have ever seen the effect on genuine coins.

PK&P say fakes are covered with 'inert materials, dust, limestone, soil and others'. I am curious what materials covered this coin.
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Old Feb 18, 2004, 04:53 PM   #4
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Quote:
Originally posted by esnible

PK&P say fakes are covered with 'inert materials, dust, limestone, soil and others'. I am curious what materials covered this coin.
I have trouble with the last statement. If an ancient reverse die was set down on a dirt/dust covered surface, and we are talking about a foundry here, it would easily pick up all types of small particles, that would be driven into the surface. And limestone dust is exactly that, an "modern" or "ancient" is not discernable. Along with other fine metalic splatter.

Bruce
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Old Feb 18, 2004, 08:00 PM   #5
wgsant
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Ancient dies did, of course, pick up miscellaneous material in the course of production and we see lots of evidence of this. It is fairly common to find references in a catalogue to a coin being "struck from rusty dies" which could of course be "dirty" dies just as well. This is not the same thing, however, as the condition on Ed's Mesembria coin. Foreign material could be imbedded on the surface of a coin as it was struck, but that would either make it "part of the coin" as Ed points out or alternatively it would leave an indentation on the coin's surface. What I am confused by is the suggestion that surface aggregation is abnormal. Why would it be any more unusual to find "bumps" of foreign material on a genuine coin than on a fake? I have indeed seen this "pebble-like" surface on coins that I believe to be authentic. I can't say for a fact that it is identical, because I never really looked at it that carefully with a microscope or had it analyzed. The next time I see one, I'll look more carefully. I guess I can say in summary that I am a bit skeptical that one can tell a fake from a genuine coin based on the surface condition illustrated in your photo.

Wayne
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Old Feb 19, 2004, 02:21 PM   #6
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Wayne, your comments are along the same lines of what I was thinking. To say that the coin is fake because of surface contamination, does not make sense. Now if there was evidence of modern tool steel - then the argument might hold. But ordinary elements is stretching things. There must be other, more compelling reasons.

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Old Feb 19, 2004, 03:26 PM   #7
esnible
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No one is suggesting the coin is fake because of the surface. Two experts (Wayne and Robert Kokotailo) have said the coin is fake because of the die.

The coin looks old to me. Yet the outside of a coin cannot be ancient if the coin was struck with modern dies. The patina is thus fake.

How are false patinas made? Dennis Kroh says "one popular way is to feed them to a goat". http://members.aol.com/kroh/fakes.html My coin does not look like it was inside a goat. I am curious as to how it was made to look old.

This is a forgery group. I've only been collecting for a few years. I am merely speculating out loud how this coin was made to look old. (I am curious how it was done.)

Under a 30x microscope the surface deposits look nothing like the deposits on my genuine coins. In my beginners' way I tried to describe the false deposits and how they differed from genuine deposits I had seen.

My plan is to get a photomicroscope and take pictures of a lot of real and false patinas. I think it would be interesting to have side by side pictures of things like genuine crystallization and 'artificial crystallization.' Real surface deposits vs the false deposits of this coin.

Perhaps the deposits on my diobol are truely indistinguishable from genuine deposits under a 30x microscope? To me that would also be an interesting result, worth the effort expended. (A useless result for forgery-fighting.)
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Old Feb 19, 2004, 04:46 PM   #8
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Try seperating the two concepts;
1. Deposits on the coin surface - we have mostly all sgreed that this is a poor criterion, unless there is something embeded into the surface that is modern. That would indicate something wasn't correct.

2. The surface itself [ie ageing] - This has several possibilities; I have some trouble with the goat idea, although I don't doubt it. stomach acid is Hydrochloric Acid, so it would be no different than dumping the coin in an acid bath, and for good meaures andd a little but of garbage. My preference would be something with CO2, heat and maybe excess humidity. This would dull the surface, the excess C02 would start the dulling, a little sulfur dioxide would add brown. It would be hard to tell from cabinet toning, and real masters of it could probably make a fine art of it.

These are more or less educated suggestions on my part. Comments?

Bruce
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Old Feb 21, 2004, 08:47 AM   #9
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First to Ed;

The tone of your last post seems to me a tad defensive. I certainly did not mean to challenge anything you said, and I probably misunderstood your comments about the "bumps" and their relationship to authenticity. We are ALL amateurs in this arena and are simply trying to apply logic to our observations. This is not a bad thing. We have seen how science alone is sometimes a poor judge of authenticity. Authentication (read that as interpretation of visual and scientific evidence) is as much an art as a science. Your high-power photos, and inquisitiveness, give us a reason to talk about things that we normally don't talk about. I'm finding that useful and look forward to more of it. Your comparison of false and genuine patinas will be revealing, I'm sure.


Second to Bruce:

I agree with your analysis of the surface conditions as they apply to the question of authenticity.


Third to those reading, but not participating in this discussion:

Dennis Kroh made his comments (mentioned here by Ed) about feeding coins to a goat some twenty years ago when most of the low end forgeries on the market were coming out of Turkey and Lebanon. Having lived in Turkey for two years, I can vouch for the accuracy of that statement. However, the coins that came out (literally) of this process wouldn't fool any of us. They were cheap cast tourist fakes. Today, most low end forgeries are coming out of industrialized nations where the threat is a little more serious. There are a lot of people in the loop between the person who finds a coin in the ground and the person who puts it into a collection. Any one of them can, and often does, decide to "enhance" the coin's appearance with the hope of increasing its aesthetic, historical or monetary value. Sometimes this is done with single coins, sometimes with a whole batch at once. Once a genuine coin is stripped of its original patina, particularly a bronze coin, it will usually be repatinated in some way to make it "seem" old again but without the original detractions. Even silver coins are repatinated or "toned" though to make them less bright and shiny. There are ancient coins on the market that have never been cleaned, but few of them are coins that I would like to collect because they are usually plug ugly. This repatination after cleaning is essentially no different than the process used to "age" a new forgery. So, it is a little shaky to use false patina as a gauge of authenticy. It is better to say that false patina is a reason to look for further signs. It is not a very reliable reason, in itself, to condemn a coin. Conversely, the presence of truly original patina is a fairly good way to confirm the authenticity of a coin. The problem is that today some forgers are getting pretty good at making false patinas that look natural to the naked eye. That is why Ed is looking so closely at the surface of his fake Mesembria diobol.

Wayne
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Old Feb 25, 2008, 04:06 PM   #10
dltcoins
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Quote:
Originally Posted by wgsant View Post
Ancient dies did, of course, pick up miscellaneous material in the course of production and we see lots of evidence of this. It is fairly common to find references in a catalogue to a coin being "struck from rusty dies" which could of course be "dirty" dies just as well.
Just a note to clarify. Regarding "rusty dies" vs "dirty" dies, rust pits the surface of the die, resulting in distinctive pimple-like raised bumps on the surface of the coin. This is most common on dies for gold, which were sometimes used intermittently over relatively long periods of time before wearing out, allowing an opportunity for the dies to rust between uses. Dies for silver and bronze on the other hand, tended to used heavily over a short period of time, wearing out quickly before having the chance to rust. Since dies are much harder the metal used for coin blanks, dirt or foreign material on a die is much more likely to affect the coin than the die, producing irregular indentations or a flattening/blurring effect on the surface of the finished coin, rather than the diagnostic raised bumps produced by rusty dies. Foreign material can, of course, certainly damage the die as well but the result will normally be readily distinguishable from die rust.

Last edited by dltcoins : Feb 25, 2008 at 04:14 PM. Reason: typo
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