uncleaned coins - before and after

I understand your viewpoint entirely.

however, using Occam's Razor (the simplest explanation is the most likely)

There are two options:
1. This particular coin somehow escaped all contact with oxygen, acidic soil, water, sulfur, and every other environmental contaminant.
2. This particular coin was very carefully conserved (@Kentucky) to the point where the coin no longer shows any environmental effects.

Conservation is very common in the art world; there are still 18-th and 17-th century restorations of classical statues that to this day are debated which parts of original and which parts are restorations. Basically, if someone is good enough at what they do, they can make it look like damage never happened.

 

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The Magnus Maximus has a nice dark green patina and visible details , I will not touch it , maybe adding some renaissance wax will improve its appearance.

The Fausta coin , if it were mine , I would take the risk to clean it.
Under the brown deposits the metal looks solid,...... the hairstyles details are pretty nice.

 

different pictures with the Sasanian coin in question :
http://museums.fivecolleges.edu/browser.php?m=objects&kv=5028580&i=3375003

https://artmuseum.mtholyoke.edu/object/drachm-ardashir-i

 

@ernstk , look at this thread to see some incredible well preserved ancient coins
https://www.cointalk.com/threads/mint-state-ancient-bronze-and-copper-coins.365252/

 

The Gallus I posted is obviously cleaned, but buy that state of preservation is astounding.

 

Question is... how?

 

@singig Thanks this post was interesting. I wonder why most of the coins which have MS preservation level are LRBs? like the amount of LRB you see in good condition is way more than earlier roman bronzes (with the exception of Titus coin in that thread)

 

Consider that most of the ancient coins in existance were LRB's.

There are a great number of Sasanian drachms on the market today that are bright and clean. It would be interesting to see how they looked when found and what was done to make them as they are now. They are not easy to photograph.
Ardashir

 

Yes your coin also looks freshly minted same way as the one from Museum. But it just makes me wonder how could that be? How could 2000 years of underground left no traces of age on these? This makes me a bit skeptical about such coins authenticity to be honest. It is just that no matter how they cleaned these, there should be traces of original patina at some areas especially protected areas around the beard or neck or in middle of characters .

 

Consider the fact that technology is improving in many ways. Coin conservattion is one of them. There is money in turning ugly billon lumps into salable coins. Most things I was told to be impossible when I was a kid are daily events now. Some of these are good; some not.

 

Ok but without any trace of age or patina, how could one know if a coin was minted and struck yesterday or 2000 years ago? There would be no indication for authenticity checks.

 

For this type of cleaning I'm using vinegar(or lemon juice) , both are less aggressive than others chemical acid solution on the market. At the beginning I keep the coin in vinegar for short intervals 30 minutes/1 hour to see how it reacts , if the results are good I extend the time interval to 2 hours .....After each interval I use bamboo sticks to remove the encrusted dirt , plus brushed under water. I repeat the process for as long as necessary. At the end , is very important to keep the coin in water for at least 3-4 days (change the water each day) to remove any acid from the coin surface, its pinky colour will fade gradually. I do not add wax immediately, I wait for a while.
Don't forget , you are taking a risk cleaning this coin , think two times before do it.

Today I will post an example with a uncleaned lot of coins(5) from the same period, cleaned three years ago , you will see how their colour has changed.

 

Maxentius AE Follis. Rome mint. AD 310-311.
IMP C MAXENTIVS PF AVG, laureate head right /
CONSERV VRB SVAE, Roma seated front, looking left in hexastyle temple with knobs as acroteria, holding globe and spear, shield at her side. Mintmark RET.



Maxentius AE Follis. Rome mint. AD 310-311.
IMP C MAXENTIVS PF AVG, laureate head right /
CONSERV VRB SVAE, Roma seated front, looking left in hexastyle temple with knobs as acroteria, holding globe and spear, shield at her side. Mintmark RET.

 

What I gather from pictures is that where metal was porous to begin with it got even more so after vinegar or lemon juice, while if the metal is smooth it remained smooth even after cleaning. Did I get that right?

 

Exactly.
Looking at your coin , the metal under brown spots seems to be smooth :

 

It's far too early in my experiments with lye to personally recommend it or draw any conclusions, but what I hypothesize is that a base (alkali), is less likely to damage the surface of a coin than an acid like vinegar. It also seems to have the benefit of leaving its own patina.

I've ran out of DW to mix the sodium hydroxide granules with after changing water in tubs earlier in the week, but once I restock, I plan on giving a range of coins a lye bath - a couple with rough patina, a couple showing porous bare metal, a couple with thick desert patina, a couple with bronze disease, and maybe one or two that don't really need it, but might come out the other side looking better.

I've given up on acids for the moment. Though I wasn't as careful as @singig, using short intervals etc, I've already wrecked the surfaces of a couple junk pieces of silver and a couple of bronzes. The vinegar seemed to attack the metal at the same slow pace as any crust, dirt, rough patina I was trying to remove and left porosity where there was none before. Lye seems more targeted, gentler on the metal, with an overnight bath only attacking the latter stuff, and with noteworthy vigour.

 

If I really want to preserve the patina , I will go to the mechanical cleaning , I will don't take the risk to clean it with any kind of chemical substances.
The ancient coins are so different , is difficult to find a recipe that works every time , you have to adapt to the situation.
I heard other people opinions on this Lye , I'm not sure that is so magic.

 

Selection of coins with wide variety of crust types/problematic patina incl. one with bronze disease (not visible in pic but coin 9):





After 3 day soak in lye with solution changed each day, scrub with a nylon brush:




Overall great results, but the votive wreath type in the top row got wrecked. I think I went a bit overboard with the 3 day soak - believe I could of got same or better results with just an over night, as it's the quick scrub afterwards that seems to really shift all the crap.

The other 9 all now look better in hand, with after photos not really doing them justice vs before photos putting lipstick on pigs. Bronze disease appears to have been cured, but time will tell.

 

A closer look at the first coin after ren wax:




Very happy with how that's come up, had no idea it was overstruck when it was dirty. Any ideas what type it was struck over?