Advice on Cleaning.

This is a rare coin by Isaac Usurper of Cyprus. It is a tetarteron that is a rare series but this one has the Virgin on the left, I have only seen it offered on market once by CNG. I have had it for several years in this condition but I am curious to what is being covered.How much detail is it missing in this condition.
My curiosity is because of this other example ( Not mine) it sold on CNG in 2014.


If I was to clean it how should I proceed?
Is there a professional coin cleaning service that anyone knows of?

 

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Please don't!

 

I have honestly not decided, I really wanted to see if it was a feasible option. I am also wondering if I am hurting its value by not cleaning it further. This is the way I purchased it. I have not touched it.

 

I would practice on some similar coins that are cheap so that
if you make a mistake it won't matter. The CNG 2014, how much
is it worth? How much is yours worth as is? I've never known anyone
to have any luck conserving a coin like yours, even the pros. If
there would be a simple or decent solution to the problem you
wouldn't see so many of them.

 

The CNG coin sold for $900.00 in 2014, mine is the only other one that I have seen anywhere. I don't think I could ever find a replacement.
It has elements superior to the CNG version, full flan, it also has some of the same faults such as the faces are gone due to its time in circulation. As for detail I am really uncertain on what is being covered. Regardless I think I will heed the advice given and put it back in the safe, I do have a microscope perhaps that could answer some of my questions without touching its current state.

Here is its brother coin, this one I have never had plans to clean, enough detail was showing. It is rare but not like the other.

 

It looks like someone tried to "clean" it with a wire brush.
If it were mine, I would soak it in distilled water for a few days, then try to pick off the loose dirt, on which you can see the wire brush marks, with a toothpick or bamboo pick. Then soak it some more and brush it with a stiff tooth brush. I seriously doubt this will damage the coin at all.
Your call.
If you do, I would like to see the results.

 

..idk...maybe clean it up a little if you must..but i'd leave well enough alone ifn it was me...

 

It can be cleaned, but detail may be lost instead of revealed. Quite a gamble especially the reverse.

 

Water and a stiff toothbrush is all I would dare!

 

Moisture might destroy the "desert patina" and there is little if anything to be gained as far as details go, as it can be seen on the areas where the dirt has been removed in a previous "cleaning" attempt.

Don't do it.

 

Exactly

 

I recommend absolutely no moisture...and the softest baby toothbrush IF you MUST do something.

I would not clean it, especially since it is a rare coin. Yikes. No. If you want a peek at what your coin may reveal, I have found that photographing the coin and then applying filters can help reveal features. Sometimes I use the filter that reverses blacks and whites and sometimes I use a tint (yellow, I find works pretty well).

I have a photo as an example ..but on iPad. I will post this and then add the photo from there in a few minutes. There it is.





When I saw the filtered photo, I saw the profile more distinctly.

 

If you don't feel comfortable cleaning it yourself, but would like it to be cleaned, why not contact your most local coin sellers to see if any of them can recommend someone who cleans coins professionally? I'm sure some of the auction houses could put you in contact with a coin cleaning service too, but I haven't tried it myself to be sure.

 

Decision made, I will explore other ways of seeing what is being covered if anything. Thank You All for the input ,especially you LaCointessa.

 

Summary - If you want it cleaned, find a professional cleaning service (I am not aware of one, but I do not have byzantines individually worth more than 50 EUR, nor unique). Do not try to clean it yourself. Best, have the professional appraise the coin and recommend a full cleaning or a cosmetic cleaning.

Now the detailed answer:

To clean or not - I do not like the desert patina, so I am subjective in my answer. I prefer to clean it off, even if this will lower the aesthetics of the coins, but I prefer the unmasked truth.

Bronze disease can hide under the dirt. Like this one (fine, this is an extreme case, but you get the idea).


Once I got the dirt off and rinsed the coin in distilled water, I noted that there was actually no patina on the high areas (head, ear, shoulder), but the coin was simply dirty, making it look like a patina. Moreover, the coin had numerous small holes (pores) under the dirt on all the surface, not only where the bd has erupted. If the bd will ever be treated, the coin could benefit of a new dirt patina, to hide the scars. Will I ever apply it? Probably not.

So, the cosmetic effect - the dirt hides not only the ugly scars, but also sometimes masks a lack of relief and improves the visibility of various elements, inducing the idea that the coin has good details and will look better if the desert patina is removed. Sometimes it will not. It will just show a shallow relief, with almost no contrast once the dirt is removed.

And last, it keeps an unstable patina in place. Happened that letters & details faded after using a soft brush (do not try a metal brush on byzantines, not even the soft brass one).

I cleaned a few hundred late romans (mostly originating from the Balcans) and a few tens of byzantines during the last couple of years. They are different in metal composition, in origin (soil their were buried), patinates differently and react differently to cleaning. Moreover, the byzantines are different in metal composition. I found that tetarterons with some silver responded better to cleaning than pure copper, and generally smaller coins responded better than large ones.

From the picture, it seems that the dirt on your coin is thick and there is some chipping of the dirt and even patina. You could find all of the above - some small bd points, unstable patina (mostly close to chipping areas), shallow or no details. Up to you to take the risk of uncovering any of these. If you do not, you cannot know if any is there anyway. Given the rarity of the coin, I have serious doubts to clean it myself and I would prefer a cleaner experienced in byzantines.

Last, one exemple of what "professionals" chose to do: scratch the sh*t off, lacquer it, sell it. So choose wisely.

 

you convinced me

 

I would reiterate what others have said and contact dealers and/or auction houses you trust and try to find a coin cleaner that they recommend. It's surprisingly difficult because often these people want to only work with people they know, and many do prefer cleaning larger numbers of coins rather than one off jobs, but if you've got a dealer you really trust they might be willing to refer you. If nothing else, a cleaner can give you their honest opinion on whether a coin can be improved by cleaning.

Don't expect it to be cheap though. I usually expect to pay $50-$100 for a coin to be cleaned by a professional, in addition to shipping costs. Factor that in as well.

 

@BenSi, I have to disagree with our colleagues on the list a bit on the question you have posed.

I seldom clean a coin these days, mainly because the coins I usually buy don't need it. But there are exceptions, and for those I rely upon a technique I developed for myself back in the 1990s. I am currently working on a denarius of Manlia Scantilla see here. The value of my coin is at the same grade as your Byzantine piece, but is more fragile and subject to defacement because it is made of silver. Read on and see what you could do with a bit of effort.

The tools are quite straightforward but will require some considerable practice to use safely and effectively: a binocular microscope and a set of different sized fine point steel needles. A 10x setting on the scope will give you the lay of the landscape, and 30x will allow you to discriminate the composition of the layers of accretion from patina or bare metal surface. More than this is too much detail for this technique, and not only unnecessary but also a step toward disaster. A lens not only magnifies object size, but also the apparent speed and distance of movement.

Here are before and after detail shots of the coin after I had worked on it for a couple of hours. The upper image is just as it was received from CNG. You will notice that there are numerous scratches already on the coin as it was received. It had been worked on by someone before me, who used a fine wire brush in his toolkit, and an apparently heavy hand. There are no noticeable additional scratches in my after shot, although some of the attentuation is due to a change in the angle of lighting. I was not interested in trying to improve surfaces, but rather to remove accretions and buildup in crevices/




The view of this coin in the shots above is something greater than 10x mag. At 10x the whole coin just barely fits completely within the field of view. This next pic gives a close approximation of what you see at 30x, the usual working magnification. Here you can also see the tip of the finest pointed needle in my kit. Notice that the needle is sharpened on a bevel, which increases its utility on auguring out embedded material.


This next shows the business end of that needle when set to work between the letters of the obverse inscription.




Here are broad views of the obverse and reverse so you can see how the original residual scratching stands against the texture of the coin's surface. It appears to me that the earlier owner who worked on this coin may have attempted to do some smoothing of the scratches s/he was inflicting, particularly on the reverse fields, but gave it off as more trouble than help. The needle in the obverse pics is the large coarse needle I use when I am skimming plain surfaces right up to the edge of lettering. As you can see, it is much too large for working out the fine crevices of figures and within many letters.





It is not necessary nor inevitable to wreck a coin by cleaning it with a microscope and needle. Key to making this work is to develop a "touch" that will allow you to let the needle come into contact with the patina or even the bare surface, without leaving a furrow on the surface. Bronze coins develop a rather hard patina, so they are fairly easy to work with. Silver does not develop the same kind of hard skin and so is very easy to scratch. Easy does it!

Fortunately for you, the coin you want to clean up of its "sand patina" (natural or otherwise) is bronze, so once you gain some skill at the technique you can remove it without too much trouble. But at that point you will be confronted by the reality of the surface as it really is below the sand encrustation.

Sometime down the road I will show you the next state of my Manlia piece after I have done some more work on it. It won't be soon, though as my plate is full at the moment. And lest there be any doubt, I only clean coins I personally own.

 

From what I see, you could save yourself a lot of work and risk by simply wrapping the Manlia Scantilla in a small piece of aluminum foil (with several holes poked Ito it by a sharp toothpick) and let it soak over night in concentrated lemon juice. Then unwrap it and brush it with a soft tooth brush. Then, use your technique on any remaining stubborn deposits.

 

Lemon juice and aluminum is safe on high purity silver coins but will totally strip bronze to bare metal and then start eating the metal. I have tried it on crusty bronze slugs.

The issue with your coin is how sound is the underlying metal? It could be porous and fragile. I agree with the advice to not use any liquids but restrict yourself to plastic and wooden picks unless you really know how to do it.

I have cleaned 100s of bronze and silver coins and I can tell you most of what you read on the internet is 100 years out of date (using olive oil) or otherwise wrong. Before ordering any chemicals and having a go I suggest reading their material safety data sheets. Some of the chemicals the old time sources and modern internet posters suggest are highly toxic with long lasting effects: such as benzotriazole. Be careful...

John