Mint State Restoration and Ancient Artifacts

[Jay GT4]

 I agree...leaving out the fact it had BD changes everything...I approve!  Great job Kevin.

[Tony A]

If the item has active BD (and is there any such thing as inactive BD?) there is NO CHOICE but to treat it. And the treatment involves using Gringott's or another chemical mix that will ruin the patina.

Patina is important, but I also don't think it's the be all and end all. Patina can enhance, but it can also obstruct and obscure important - and artistic - details on coins and artifacts. I wonder how many coins have been mis-attributed simply because significant features have been left hidden for the sake of the patina?

As for MSR ... Well, I've have success with it - and if used carefully and monitored closely - will clean coins and items nothing else works on AND leave enough of the patina to keep most collectors very happy. MSR isn't my first choice most of the time, but it has proven to be very useful in some situations. Here's my observations on it:

1. MSR is extremely effective on coins and artifacts with those nasty encrustations that extended soaks. boils, and Gringott's don't work on. The coin may be stripped of it's patina, but it shows fine detail and is easily attributable. If it's a choice between saving the patina by keeping it a slug or a "maybe something" and stripping it down to get to the prize underneath that I can display, I'll go with MSR every time. (And I'm not talking about eBay slugs, these are good coins with bad encrustations.)

2. Using a medical syringe and carefully monitoring the process (checking the small treated area every few minutes), MSR does a good job for spot cleaning on those bad spots.

3. MSR is also good for cleaning silver washed coins when the patina is hard and even a soft brush or pick will cause more harm than good.

I was talking to some very respectable dealers recently and they were wondering (as I do)  why patina is such an issue considering the sheer volume of coins sold in Europe and the US have been repatinated?

Tony

[Tony A]

I have to ask those who are telling us that auction houses and museums clean items but leave the patina. Can you tell me how they do it  since cleaning, by definition, will remove the patina? We have had a lot of discussions regarding the regular use by archeologists and museums of harsh chemicals to clean coins and artifacts - I've talked to archeologists and they readily admit it (even if they do it with their head down in awkward sort of shame). So is it just "some" auction houses and "some" archeologists, or is it most to all of them? As it is with a significant portion of coins being imported from wet climates (Eastern Europe and Europe), chemicals and rock tumblers and other rather harsh methods are used before shipping ---AND re-patinated! And just how many dealers - or museums, for that matter - are going to conduct an acetone test before putting an item on display or up for sale? I'm afraid the use of MSR or other chemicals and patination are far more common than we care to admit. (And MSR and other methods will leave enough of the original patina to make authentication possible. Virtually nothing will remove all of it.)   

A few museums (very, very few) and auction houses (if any) have the budget and resources to spend months and years on the type of cleaning (or non-cleaning) being advocated by some members here. The 2nd picture may appeal to a lot of collectors, but I doubt there is the same attraction for the vast majority of visitors and customers. People want to see the details, and not some elephant man looking artifact lacking definition for the purpose of saving the patina. Museums want visitors. Sellers want customers. And Kevin wants to sell his little statue. Sadly, that often requires damaging the patina. (And re-patination, too.)

Tony

[Lee S]

Well said that man!!!!

    Like I said earlier... Patina is obviously a valuable and beutifull thing, to be desired on an atifact ( or ancient coin.) , but give me the choice between a green lump with original patina and a wonderful piece of art from millennia ago with a stable surface , I know which I will choose...

     My cleaning of coins is always done with the intention to keep patina intact. Except where it is impossible, in which case, I don't... And admit it. On ancient artefacts like the one features here I think it is even less important. What is important is the beauty to the eye of the buyer. And if I had the money , I would like this piece. Therefore.. ( in MY world ) the restoration job was perfect.

[benito]

IMO something more could have been done before reaching step 3.

[Roma_Orbis]

    Thanks 4to2CentBC for the link to Royal Athena. It's a eye-popper! Too bad my little Jupiter is missing his arms and legs, huh? He'd fit right in with the others.

You must be kidding. How fortunate were Royal Athena, Christie's, Bonham et all ancient art objects for sale to have escaped your hands!

[Tony A]

And what was the state of these little statues BEFORE Christie's got a hold of them? Or did they just come out of the ground looking like that? (BD-free, too.) Somewhere, at some time, someone cleaned those items - and the overwhelming odds are that the cleaning was done using MSR or some other chemical - and how do we or anyone else know how many of these artifacts were not re-patinated? It's not that hard to do, and I'm pretty sure no one "in the know" will give us a definitive answer. Without knowing the original condition of the artifact and how many hands it passed through (and what they did to it) before Christie's got a hold of it, the statement that "this is how they do it and the condition they sell it" doesn't hold a lot of water.

Too bad these items are rare enough that it's almost impossible to do a controlled experiment to see which would sell for a higher price, but I'll put my 2 denarius on picture #3.

Anyway, unless you're digging all your coins from the backyard, there's really no way of knowing how they were cleaned and which ones were re-patinated somewhere along the line - and the odds are that a fairly sizable portion of any collection these days has been cleaned and artificially patinated at some point. (And I doubt even the hardliners here won't venture an acetone test to find out, either - and fewer sellers will be willing to discount their "suspect" coins. And fewer still would discard a prize coin simply over lack of an original patina.)

Tony

[Platon]

I think it is best to leave as much of the original patina intact as possible, both for aesthetic and historical reasons. BD is certainly a pain (as I am learning more and more about after each uncleaned lot I go through) but I would try everything I could to keep as much of the patina as possible. In this case we do not have a picture between stages 2-3 to see what the statue would've looked like after BD treatment but before the rest of the patina was taken off, so who knows if the better move was to try and salvage the remaining patina.

I don't support the view that whoever owns an ancient object can do what they like with it. These are ancient objects that are much older than us (and if treated correctly) will be around much longer than us. They are more correctly (in my eyes) pieces of human history that we might take ownership of for a few decades, but we cannot do what we want with them and instead we must preserve these beautiful objects for future generations in the best possible way. I'm not going to accuse anyone of wrongdoing in this particular case, the BD is a threat to the object's existence so something had to be done about it, but I am also not sure (with full due respect to Mayadigger!) that this particular restoration job was the best possible solution to the BD problem.

But of course we also have to be realistic and not every object can be professionally restored. Attached is an image of the relatively recently discovered dancing satyr statue. The restoration job makes the item look as if it were recently discovered while also maintain the preservation of the piece, which I believe is the ideal people working with ancient objects should strive for.

[Andrew McCabe]

Starting about two years ago, I recall getting into debates with top-level coins in hand where dealers/experts plumped for the coin with significant remaining original surfaces as being far more preferable commercially. I recall a discussion about a sestertius (which we were handling) whose surfaces looked as pleasant as that of the bronze statue jimmynmu showed, lumps and all. A less-experienced numismatist on joining the discussion suggested to clean the coin a bit more as he thought it would look more pleasant. The reaction of those who knew the market better was "you must be mad, leave it just as it is". On another coin discussed at the same time, it had been more thoroughly cleaned. On the latter, there were sighs of regret, because the more thorough cleaning robbed the coin of part of its authenticity, and would inevitably start collector chatter about whether the coins beautiful surfaces had been improved. The market then spoke. The net result was that relative to the first coin, the second sold at 50% discount (the first sold at 3 times estimate, the second at a little over estimate). My recent attendance at a series of auctions confirmed this as a growing trend: collectors are placing more and more value on (a) provenance and (b) less-cleaned coins. Greater levels of attention were in evidence around coins that had had greater levels of cleaning, not only because the cleaning, as such, detracted from value, but also because bare metal surfaces can be tooled more easily without detection. Of course some will be thinking of repatination, but experts are pretty well able to distinguish between MSR-dipped-and-then-repatinated, and naturally patinated coins - they are not fobbed off by Sadigh-gallery type new patinas. The thing about cleaning is it's a one-way process. Reversing is very slow.

I was bidding yesterday on the below dark-coloured denarius, though probably not remotely high enough to win it (pray for me, but I think it was hopeless, it is such a wonderful coin). From the coins which accompanied it, all as dark, and many of which were even darker, and from the collection description ("from an old collection") I deduced that these coins hadn't been cleaned in at least 100 years. Wonderful. Both for the inherent value and for how the coins look. Someone will chime in and say that you can get the same effect with Deller's. I don't think you can. Someone else will think the coin more beautiful if dipped and made shiny. No. It's magnificent just as it is.

[SC]

Kevin my friend.  I am afraid you were not being fully honest with us.

Your second image does not show signs of BD.  And in the accompanying message you only stated it was "unacceptable".  

If that judgement was made solely on an aesthetic basis, for example because it had an uneven patina, then you made one type of choice.  One that it seems most here would not agree with.  On the other hand if it still had active BD requiring immediate treatment then you made a different type of choice.  

You should not have left those facts out of your initial post.

I agree that an object that requires immediate BD treatment must be treated and then salvaged afterwards and such salvaging might require options people would not otherwise support.

But I disagree strongly with those who imply that heavy corrosion can't be treated without destroying the patina or that all patina on nice objects at auction are due to re-patination.

Here are several examples from my collection.

This first item is a bronze statue of Eros.  It was harshly cleaned, long before it came to me.  Looking at it under microscope I can't tell if it was cleaned manually or chemically or through a combination of both.  It does not appear to have been treated with Dellars as the darker bronze is clearly a hard natural layer over the bright brass bits.   I will let it slowly re-tone.  At least it was cheap due to its state.

Next is a statue of Fortuna.  This is heavily pitted.  It is from the "Holy Land" and I was told it was a maritime find.  I am pretty certain that whatever patina it had left in its pitted state it was stripped and then poorly re-patinated.  Not only does the bright green look unnatural but it is in some of the pits too.  I think someone applied an artificial patina and then tried to wipe it partly off to give it a realistic look and failed miserably.  I could be wrong and it could be some natural outcome of exposure to the sea but I doubt it.  Not sure what to do with this.  I think I will leave it as it.  In any event it too was cheap as it is ugly.

Shawn

[SC]

Now two busts.

The first is Serapis. 

He was mechanically clean in ages past.  You can see he is mounted to an old wooden base.  It came from a collection dating back over 50 years.  He was never treated chemically.  He could be cleaned more using mechanical techniques but there is no guarantee of a nice surface underneath or that it wouldn't re-ative some BD.

This is exactly the type f item that seems to divide collectors.  Is it done or still uncleaned.  As far as I am concerned it is done and won't be touched unless it grows BD.

Next is a bust of Minerva. 

She was cleaned mechanically.  Again not by me.  No signs of ever having been cleaned chemically.  Encrustations were removed down to this green-bronze, almost black, layer.  However, there are still greens and dark reds here and there.  Also there are still small encrustations in many of the details and these are the lighter green too.  Thus the patina is far too complex to have been a re-patination.

Shawn

[SC]

Now we get to my pride and joy.  My Capitoline Jove.

This statue (118 mm tall) comes from a famous collection in Vienna and was found in the 1970s.

It was mechanically cleaned but was not stripped and re-patinated.  What you see is a dark brown layer of natural patina.  I don't know what it looked like when found in the 70s.  Perhaps this was under encrustations, perhaps not.

I have included three shots from my USB microscope.

The first is the right eye.  At this level of magnification you can see that the patina is not actually even.  There are thicker bits, lighter bits, ancient dirt layers, etc.

The second is the left eye.  You can actually see that the eyeball was silver plated.  On larger statues it was usually silver-inlay.  No real trace of the silver plating was left on the right eye but some does remain on the left nipple (not shown). 

The last is a shot of some of the scratches on the torso.  Here you can see the fact that dirt or some thin layer remains with the dark brown patina underneath it.

Shawn

[SC]

Finally, a cleaning example. 

Unlike the other items this is an item I actually cleaned myself.

This hollow bronze finger is 82 mm long and was from a larger than life-sized statue.

First is a before shot.  Not the best quality but you can see that it had fairly heavy encrustations.

Next is an after shot.  This is after around three hours work with only a head magnifier, a scalpel, a whetstone (to keep scalpel sharp), and a silver bristle brush.  All encrustations, dirt etc are gone but what remains is still a nice green patina layer.

Finally a close up again showing that the patina is, as usual, not actually even when seen under magnification.

Shawn

[4to2CentBCphilia]

Anyway, unless you're digging all your coins from the backyard, there's really no way of knowing how they were cleaned and which ones were re-patinated somewhere along the line - and the odds are that a fairly sizable portion of any collection these days has been cleaned and artificially patinated at some point. (And I doubt even the hardliners here won't venture an acetone test to find out, either - and fewer sellers will be willing to discount their "suspect" coins. And fewer still would discard a prize coin simply over lack of an original patina.)

Tony

I have read numerous threads about wonderful desert patinas. People stumble over themselves in a rush to praise that beautiful desert patina. Of course, it is also well established that many of these desert patinas are artificially applied. In fact, some of threads have been specifically about an artificially applied patina.................and how wonderful it looks. Apparently, the sanctity of a coins surface is relative. Relative to what.....I have no idea. I get the sense that nobody else does either.  Smacks of hypocrisy to me.


BTW People used to love all the smoke, dirt and muck covering the frescoes in the Sistine Chapel. Made it look old and somber. Gave it gravitas. THIS is how a masterpiece is supposed to look. REALLY? Says who?  The artist had a very different palette in mind. Bright colors, a celebration of color.  Thankfully, greater minds prevailed and today we see the work as it was meant to be seen.

Patina is by definition, tarnish. No different than the crap that covered the frescoes. It wasn't put there by the artist. If everyone here is arguing that something, originally applied by the artist, has been removed. That is one issue. But every indication is that folks are crying over a removal of tarnish. I will say this again...............and the market proves this...........if the objects date is undisputed, patina is not as important. There are plenty of very expensive bronzes in museums that were uncovered a century or earlier, cleaned in a manner that would make many shudder, repatinated....................and guess what, we all love them (in apparently blissful ignorance). This little Jupiter IS NOT some unique artifact that will undergo scientific analysis to determine its age. Nor will it be studied for minute detection of ancient varnishes or paints. It is a relatively common Roman statuette, with missing extremities. However, it is being held to a higher standard than million dollar artworks in museums. There is a rudeness to some of the comments that I find surprising.

And bronzes are not coins, just like ancient coins cant be compared to modern coins. SO............stop comparing cleaning coins to cleaning bronzes. Apples, oranges.






 

[SC]

The artificial desert patina that is applied by some dealers is not a true patina.  It is not a tarnish, corrosion, or chemical reaction.  It is a light coating of thin mud, more lightly coloured than the coin patina, that is washed on the surface to provide some contrast in the details.  It can be washed off.

"Genuine" desert patina is a combination of a black patina (a cuprous chloride reaction to the surface of the coin) combined with original dirt that has been partly, but not fully, cleaned off.

Shawn

[4to2CentBCphilia]

I am completely aware of this and it does not change the point of my post. I point out in my post that few people discriminate against a artificial desert patina. They know it is artificial and don't care. They pay high prices for them. I could point out a few threads here regarding some of those coins, but I won't. My point is that all this crying about patina seems to be highly subjective. If someone can prove otherwise, give it your best effort. I'm all ears.

[Jay GT4]

Desert patina as was mentioned is not patina at all but dirt.  Real patina is part of the artifacts history.  As I mentioned on page one, look at the Riaci bronzes.  It would be easy (and cheaper) for them to strip the patina along with the encrustations and then "restore" them but they aren't doing that.  They are meticulously cleaning while at the same time leaving the patina in tact.   They are two of the most important bronze artifacts that have come down to us.  They may have already been hundreds of years old when they were lost off the coast of Italy destined for Rome.  Did they already have a patina on them when they were lost at sea?  Chances are yes, just like modern sculpture (and gutters and flashing) take on a patina after being exposed to the elements...

[areich]

I think most people are not aware of artificial desert patinas. I doubt the person who paid $100 for a common Late Roman with glued-on sand will 'not care' if he ever finds out. An artificial desert-patina, if you don't know about it, i.e. if it is well done, is just as attractive as a genuine one but I wouldn't want one on my coins. I can't remember anyone here praising a desert patina they knew to be false but many accept these uncritically.

I don't get the point about hypocrisy, here the same people as always are arguing against stripping the patina and the same as always think it's just fine. Those are the same people that have nothing against repatinating coins either.

With this piece, the patina is even more important, since, as you rightly say, it's no work of art that can stan on its own. If it wasn't old, it would be considered tacky. But it's still a nice piece, and the cleaning, even if I would have wished for less of it, was skillfully done

[Jay GT4]

areich +1

[Andrew McCabe]

here the same people as always are arguing against stripping the patina and the same as always think it's just fine. Those are the same people that have nothing against repatinating coins either.

 

Yes. After an afternoon working with my turtles (the animals, not the silver coins), I thought to come back and add a comment, which is: No-one's views have been shifted by this discussion. We've all stated our point of view, and no-one has moved. No problem.

Here's a deal I propose:

1. I get to keep my collection of coins, which I consider beautiful, and that includes deeply toned, sometimes black, silver; and bronzes that invariably have deep and colourful coatings of natural metal oxides built up the centuries, and sometimes a bit of external dirt.

2. Those who like their silver bright and their bronzes metallic get to keep their coins, which they consider beautiful, and to do whatever they like to them.

3. I may not buy your coins if I think them over-cleaned.

4. If you buy my coins you are free to do whatever you like to them.

[Mayadigger]

Ave!

Kevin my friend.  I am afraid you were not being fully honest with us.
Your second image does not show signs of BD.  And in the accompanying message you only stated it was "unacceptable".  

    Shawn,
     It was just a simple post to show a few before/after pix. I never occurred to me that my every word would be so heavily scrutinized. Sheesh. And, yes, I did believe that the mis-mash of patina was ugly and 'unacceptable'. And, yes, after the 2nd photo, I did use a few delicate DD's rubber smoothing tools to attempt even it out without removing it. And that that's when the BD pockets began to show up. At the time, it never occurred to me that I should take more photos of the BD Jupiter to please Forum members. I wasn't making a 'cleaning chronicle', after all. For you, of all people, to suggest that I wasn't being truthful in any manner is shameful and I'm disappointed that you'd even bring it up.

However, it is being held to a higher standard than million dollar artworks in museums. There is a rudeness to some of the comments that I find surprising.

    4to2CentBC,
     Rudeness is quite common on this board, my friend, such as comments like:

How fortunate were Royal Athena, Christie's, Bonham et all ancient art objects for sale to have escaped your hands!

     Granted, Andreas and I have locked horns upon many occasions; we are long time friends and 'agreed to dis-agree' years ago, but personally directed comments are not what anyone wants here.
     As Andrew has noted below, to each their own. No one is going to change their mind.
     Once again, as a reminder, we began with the subject of using MSR on ancient artifacts and it turned into more 'I'm right and you're wrong', 'my way or the highway' diatribes...with desert patina thrown in. So, if possible, can we return to the original subject?
     Andrew, early on you mentioned something like 'if this is what MSR does to coins (artifacts) it's no good.' After everyone saw the final version the blitzkrieg began. True or false? You, Andreas, and many others commented positively on the mid-one, saying that it looked much better before the stripping, etc. Again, true or false? I think what you all forgot was that it was MSR that got us to the second version in the first place. Had we only shown the first and second examples, would this have changed your opinion in anyway? Be honest with yourselves.
     I also find it interesting that no one had any comments whatsoever concerning the before/after pix of the small Egyptian statuette. Trust me, folks, there was no patina to be saved under the horrible crystalline encrustations other than BD.
    From Shawn concerning his Fortuna-
    

I am pretty certain that whatever patina it had left in its pitted state it was stripped and then poorly re-patinated.  Not only does the bright green look unnatural but it is in some of the pits too.  I think someone applied an artificial patina and then tried to wipe it partly off to give it a realistic look and failed miserably.  I could be wrong and it could be some natural outcome of exposure to the sea but I doubt it.  Not sure what to do with this.  I think I will leave it as it.  In any event it too was cheap as it is ugly.

    Shawn, your Fortuna has not been 'artificially' anything. Those encrustations cannot be faked and it has certainly been underwater, but not necessarily saltwater: more like freshwater mud/muck. (I've taken the liberty to Photoshop yours with mine for comparison.) Ugly and cheap is no never mind, but doesn't it bother you that the metal beneath the encrustations (it's not patina) is rotting away while you dither about what to do with it? I only ask because bronze artifacts that have spent centuries underwater are intrinsically unsound. Muck/mud/clay tends to actually help preserve them, but once removed into a dry climate, the rot/BD tends to exert itself. Just askin', my friend. Again, which would you prefer in the long run - your Fortuna rotting away 'as is' or to have it preserved/restored? As seen in the photos below, your Fortuna could look similar to our 'after' photos, or do you and others truly believe that it's better to just let it just rot away 'as is' rather than being saved/restored to give it life for another 2,000 years? Perhaps we could take vote and let other's decide for you?  
     Look, folks, I'll admit that I'm no Museum expert when it comes to cleaning/restoring ancient artifacts and am always happy to receive advice from those who have more experience. Back in the day when I was an Executive Chef, the term for those who thought they knew the 'in's and out's' of the Kitchen but didn't, were referred to as a 'Schumacher'; IE a shoemaker. In this case, I'm a Schumacher and I am willing to admit it.
     That being the case, perhaps in the future we can limit any comments/criticism to those that have actual experience in cleaning and restoring ancient artifacts?
     Best regards from your Schumacher friend,
     Kevin

[areich]

Kevin, I think you got confused with the many quotes. 

[Mayadigger]

    Ya think?  

    It's not all about the negative quotes/comments, my friend. We're thick-skinned and have become used to it by now. It's more concerning the comments from those that have zero experience (not like you) concerning cleaning/restoring ancient artifacts (not coins) who simply make a negative post and then move on without a care for our advise. I still feel the hurt that after all these years on Forum (How many years have we been here, anyway? 12 or more?) and we still get bombed, no matter what we advise. Your comments are always received with the best intent and keep us leveled, savvy? IE your earlier comment below (and I know this was meant directly for me and I'm cool with it, btw)

I don't get the point about hypocrisy, here the same people as always are arguing against stripping the patina and the same as always think it's just fine. Those are the same people that have nothing against re-patinating coins either

    Andreas, I'm not a hypocrite. I simply understand that you and others have a original-patina fixation that goes far beyond my understanding. In a number of email conversations with Curtis Clay (HJB), he'd rather see a re-patinated coin/object with full and complete details versa a blurred and uncertain original patina, but that's another subject. Who am I to discredit Curtis Clay? You can write him and ask for the same question.
     I value your opinion over most as you certainly know more than others. What is your thought concerning the two afore-mentioned artifacts?
     Best regards,
     Kevin
 


    

[arizonarobin]

Generally I lurk and tend to stay away from hostile threads  However I have used MSR and would like to make a few observations.

I would just like to say a few things about MSR.

A "dip" should be defined, as I hear this term used with MSR in this thread and others. You can dip (dictionary meaning of dip: To plunge briefly into a liquid, as in order to wet, coat, or saturate) a coin in MSR and nothing visible will happen. It should not strip the patina off from being in a few seconds.

To get results the coin or object has to be soaking in the MSR for a length of time. Now this length of time depends on the coin, condition, dirt and patina.
I have never put a clean coin in MSR, but I have tried it with crusty and uncleaned bronze coins and also a silver denarius with horn silver lumps.

As with using anything other than distilled water, you must be careful and watch the coin. I have not had any problem with short baths in the MSR (10-30 min), then soft brush, repeat. (Then soak in distilled water.) This method for me did not remove any patina. (much like going from Picture one to picture two in the OP pictures)

On the one denarius with horn silver, it did not have any toning or patina to begin with just large red lumps. I would gather someone had already tried cleaning the horn silver off and were unsuccessful. The MSR did remove all the ugly lumps off my coin and I was very happy with the results.


HOWEVER: MSR will take the patina off if you leave it in too long, or if you have an extremely delicate patina. You can not just soak a coin in it or leave a coin unattended.

I personally do not use it anymore as I prefer to leave my coins soaking in distilled water and not have to worry about how long they have been in. I have too many distractions to sit and watch a coin soak. 

I prefer my coins with the patina intact but I'm not a purist about patina. I will buy a coin I like, especially a rarity with or without its patina and love it just the same in my collection.

Robin

[Tony A]

Robyn - Glad to know someone else did a little experimenting BEFORE overgeneralizing and writing MSR off without finding out for themselves. Your results seem to be more or less what I've come up with. I didn't mention the MSR dips, so thanks for bringing it up. But as I stated: MSR is very effective for SOME coins under SOME conditions IF carefully monitored. (I only let the really nasty ones sit for more than half an hour and as soon as the crud starts breaking up, I carefully observe it every few minutes. And the monitoring really is an imperial pain, but ...)


As for cleaning without damaging the patina ... I still want to know how that occurs! The dirt and crud are bonded to the patina with variable consistency (and the patina doesn't have uniform consistency either!), so any time a coin or artifact is cleaned a portion of the patina will be removed as well. I mean, it's not as though there is some stratification between the "dirt" and the "patina". The dirt IS the patina, just usually somewhat older dirt, grime, sweaty handprints, air pollution and whatever else the coin or artifact was exposed to before the outer layers bonded to it. The real art of cleaning is simply (although it's anything but simple!) removing the unwanted dirt and leaving the "good" dirt. But it's still dirt.



Tony