Help me to save a rarity - proper xylene usage instructions

Hi everyone,

I have recently come across a gem of the highest rarity but it is currently impaired. The coin is a diamond in the rough that I believe can be transformed into something majestic. As can be seen from the images below, the coin was submitted to PCGS by its previous owner only to to be told the coin needs to be conserved due to the overwhelming presence of PVC - PCGS is indeed correct in their assertion. I purchased the coin realizing that the coin is in fantastic state of preservation and could be vastly improved with a proper acetone bath (something I have done countless times before, with great success). To my great dismay, after a good week in acetone, the PVC residue persists. In my decade of collecting, I have never come across such a case (and I have been through quite a few coins). After the acetone bath, I took a Q-tip and attempted to gently rub away the green to see if it budges... it does. After a few rubs, the Q-tip became quite green and a truly beautiful undertone/skin of the coin could be seen - it's almost proof-like in appearance. What little I wiped with the Q-tip naturally produced very faint hairlines (given the proof-like reflectivity of the fields) so I stopped and began searching for a better approach.

After extensive research and reading, mainly at CT, I have come to conclude that the next logical step to take is to use Xylene or Toluene. Posts by GDJMSP and BadThad have been highly educational and I hope they and others see this post and offer a bit more guidance.

My questions are as follows -

1. Given the images below, which do you think is more appropriate for a next step, Xylene or Toluene?
2. Can you please elaborate on the precise procedure (I'm aware of the risk and the requisite safety measures).
3. Any particular set up you recommend? For coins I bathe in acetone, I use small glass mason jars and a pair of steel clamp tongs. This has worked for me quite well.
4. How long should the bath in Xylene/Toluene be? Minutes? Hours? Days? This particular sort of PVC seems very persistent so I'd assume a through prolonged bath is needed initially and then perhaps a secondary/tertiary baths with a final acetone bath?
5. Any other tidbits you recommend based on experience would also be greatly appreciated.

Original State


Method & Coin After A Week Long Bath

 

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I would soak the coin in one final acetone bath for an hour or so and stop there. No more rubbing. The hairlines are already bad enough to keep the coin from grading. Sorry but I don't think the coin can be improved at this point. Q-Tips have killed way to many coins. Xylene won't harm the coin but I don't think it will help any.

 

GDJMSP - thank you for your invaluable input. I did notice exactly what you note (the edges of the coin) and I suspect, though I am not certain, the coins suffers from both, a lot of PVC (PCGS certainly believe it's PVC though they may certainly be wrong) and perhaps some verdigris.

I would never use Verdi-Care on this coin myself as I have neither the experience nor the knowledge of the product. I know improper use of Verdi-Care is a GREAT way to kill a coin. Given the extreme rarity and value of this coin (https://www.ngccoin.com/price-guide...0-grana-km-213-1791-cuid-1148176-duid-1487256), I'd avoid Verdi-Care at all costs. The reason I am strongly leaning towards Xylene/Toluene, is because I understand one is unlikely to damage a coin with those products (at least a silver one - I know how you feel about copper).

As for my goals - I want to bring this gem back to life. It's dull and dead now. Would I slab it in the future? Sure, why not but that is not a consideration for the moment. I wholeheartedly believe that if this "green" is properly removed, this coin can grade in the high AU or perhaps better range. I urgently want to prevent any further damage (and I think the week long acetone bath should have accomplished that) and secondly after gently rubbing with a q-tip, I am able to see what's underneath the "green" and it's quite beautiful. The coin has luster and field reflectivity one would find in a prooflike coin. It doesn't look it now because of two reasons:

1. I can't capture it using my amateur skills and my phone
2. the coin is still substantially covered with the "green"

Let me ask you this - if the green substance is verdigris - would it easily come off using a gentle rub of a qtip after an acetone bath? My understanding is that it would not. Whatever it is, the acetone softened it enough for it to come off relatively easy. This is why I'm leaning towards PVC. It just seems the acetone is not a strong enough solvent.

As for comments from ToughCoins and Idhair, thank you for your input but please understand you are comparing apples and oranges. You are looking at the original images taken professionally by the auction house and comparing them to my over-exposed images with bright white light beaming at the coin. I use this light to closely examine coin imperfections and when looking at them with such a light, even the slightest blemishes show up as craters. Hairlines not easily visible to the naked eye also readily appear. Here are a couple more images with natural lighting:

 

I disagree as well. You killed the coin using Q-Tips. Put them away. Don't touch the surface of a coin with anything.

 

"Killed the coin" is a little harsh... you seem to think I took a box of q-tips and used them to scrap off the pvc or whatever like one would use a Brillo pad on a dirty pot. After the soak, the I just took one Q-tip, dipped it into acetone (so that the cotton is fully saturated) and gently ran over several spots to see if the residue comes off and it came off rather easily. I don't know what state is the coin's true skin underneath all the green, but I'm of the opinion it's much more attractive than the current dull, lifeless, veneer I'm seeing now (even if it previously has been cleaned/dipped).

Nothing was "Killed". I've been collecting long enough to know what a "Killed" coin looks like and what I hold in my hand is certainly not it. You're certainly entitled to believe what you wish, but at the end of the day, all your opinions are based on images that I posted... I'm the one with the actual coin in hand.

 

Ignore me. I'm new at this.

 

At this point I suggest leaving the coin alone and not take any further steps. Observe it over time. It should tone down. Don't rush the process. Let time do its thing.

BTW: that's a beautiful zodiac piastre, one of the best that I have seen in a long time. Congrats!

 

Thanks Robin - appreciate the kind words. I've seen many a zodiac piastra pass through the auction blocs of the years and just about all have been either extremely circulated, problematic, or both. The jury is still out on whether or not my specimen is problematic (as of right now, with all the "green" it wears, it certainly is) but I'm hopeful.

I do have a question for you - if xylene is stated to not hurt a silver coin, why do you have such an aversion to me giving the coin a good bath to remove a substance I wholeheartedly believe is PVC (there certainly may be some verdigris in the mix as noted by GDJMSP)? Are you just averse to using chemicals (acetone included) in general? What are your concerns? We know what the intended consequences we are looking to achieve are, so what do you think the unintended ones could be?

 

I wish you'd have asked before the q-tips, we'd have told you roll, don't rub.

 

1st Beautiful coin, i've seen many in rough shape but yours is very sharp xf if not au but...

This is rough.. I am one of Verdi-care's biggest supporters but that's with copper. BadThad is the expert (and creator of) where Verdi-care is concerned. I have considerable experence conserving coins both worthless and of some value.. But that is NOT a coin I would even dip myself as you have done. My best and heartfelt recommendation at this point is do nothing more.. if the green bothers you that much send it to NGC for conservation, while the NGC slab may not carry quite the premium of PCGS, their conservation group is top notch and not overly expensive even with the value of the coin. Just please do no more yourself before you do serious damage.

 

Basically, I think that a long soak in 100% acetone should remove all PVC residue. If there is still some remaining, perhaps a second soak is in order. Acetone is a powerful solvent, and I find that it effectively removes PVC residue very quickly.

Now the after photos of your coin indicate to me that the PVC is gone. Did you rinse the coin with distilled water? Using tap water may introduce chemicals, such as chlorine that may affect the surface. Distilled water is best.

Are you concerned about the darkish lines running across the obverse and reverse? Those are very light deposits of silver oxide, possibly some kind of chemical interaction with an envelope in which the coin was restored.

I've never used Xylene or Toluen so I cannot give you any advice for these chemicals.

There is one chemical that is used by ancient coin collectors to remove horn silver, thick black deposits that occur on silver coins. This is sodium thiosulphate. It usually comes a small tablets that are dissolved in hot distilled water. This chemical is very effective in removing black deposits without affecting the coin's surfaces. However, depending on how thick the deposits are, there might be corrosion underneath. Given the very light color of these lines, that is probably not an issue with this coin.

If you do use this chemical, I would suggest that you test it on an inexpensive coin to see the results. It does, based on my experience, leave the surfaces intact as far as mint luster is concerned. The trick is to rise the coin quickly and thoroughly with distilled water followed by drying in a soft towel - no rubbing.

Cotton swaps are pretty safe to use if they are used to lightly dislodge deposits. I use them extensively on ancient and modern coins without any adverse results.

Here's a thread that discusses sodium thiosulphate:

https://www.cointalk.com/threads/how-to-remove-encrustation-from-r-r-coin.348784/

Hope this helps, and good luck!

 

Thanks for that GD - much appreciated.

I never do; I don't even handle them with my hands aside from holding them on the edges. I just wanted to see the nature of the "green" as I was very surprised when the acetone did nothing. I wanted to see how easy it was for it to come off. I generally buy high end/well preserved coins so never really came across this level of accumulation before. I guess my initial assumption of the green being PVC was ill formulated. What you say with respect to verdigris certainly makes sense.

The more I contemplate what's been said here the more I'm inclined to explore verdicare. But before I even broach that path, I have MUCH research and learning to do on the stuff. If you or someone could point me to a good thread that outlines proper verdicare procedures on silver (if there is such a thing), i would greatly appreciate it.

Also - is Thad around? - I would love for him to chime in here.

Robin - thank you very much for taking the time to share with me your immensely helpful insight.

To answer the above two questions - no, I didn't use distilled water (I generally don't as i don't see the point or have I've never had the need - I much prefer acetone) and no I'm not at all concerned about the black line running on the devices but rather the "green".

I've never heard of sodium thiosulphate but will gladly read about it. I highly doubt I'll use the stuff but for the sake of "science" and sheer curiosity, i might buy a "clunker" coin and try it out.

 

GDJMSP just covered most of it. You removed the plasticizer residue with acetone, that was a good first step....but...you should have stuck with just soaking to avoid potential physical damage. A non-polar organic solvent (xylene, never use toluene!) will not remove or treat the verdigris. I see your choices as:

1) Attempt profession conservation. If this is very valuable coin, you probably should have just left it to the pros. After q-tips it may be impossible to save.
2) Dehydrate the verdigris with acetone and put the coin into an airtite holder. This will keep it mostly in check.
3) VERDI-CARE™ to attempt to remove the verdigris and, if it won't budge, at least it will freeze it where it is.

Good Luck!

 

Much obliged Thad. Looks like I have some research & thinking to do.

 

Does anyone know how PCGS would "restore" a silver coin like this one