Clean a drachm?

I know it's not the best example (haha) - but I have wanted one of these for a long time and this one I could afford.. and I am very happy to finally have one!

As you can see it could probably do with a bit of a wash.
Is this just a distilled water bath and a rub with a soft towel - or is there another way to clean ancient silver?
I don't own many silver coins.. so new to me.. thanks for any suggestions..

 

Log in or Sign up to hide this ad.

Some of those encrustations look fairly stubborn and won't come off with a distilled water soak. The coin is pleasing as is. My advice - leave it alone or you'll risk ruining it, especially if you are new to cleaning silver.

 

I agree with David. Cleaning silver encrustations is tricky and involves some home made chemistry using aluminum foil and lemon juice. I'd leave it as is...

 

Thanks for the responses (and I welcome any more opinions).. I will not do anything that may damage it in any way. As stated this is new to me .. so if someone had a method that was 100% reliable and considered standard practice, I would think about it. Otherwise I will leave it.

Here is the stuff that comes up when I Google this.. seems very scary to me (and over the top!)... but what do I know? Any chemists in the house?:

1. Without a doubt the best way to get an amazing bright finish on ancient Silver coins is to use Sulphuric Acid. Sulphuric acid does not in any way react with Silver therefore it will do absolutely no damage to the coins whatsoever. You need to do this in a well-ventilated area, wear rubber gloves and appropriate safety equipment including goggles and a mask. Use an old heatproof bowl and add boiling water to it. Wrap the coins individually in Aluminium foil shiny side facing in and drop them into the hot water. At arms length then pour in some Sulphuric acid, you wont need too much and will get used to how much to add after you have used this method several times. There will be a reaction with the aluminium and the hot water, and some smoke will come off the solution for several minutes. After a few minutes the reaction will cease and you can remove the coins with a pair of long nosed pliers. Rinse them under a tap, unwrap them then rub them between your fingers with baking soda. Sulphuric acid can be purchased from most hardware stores as it is commonly used as a drain cleaner.

 

Few things are 100% reliable or 100% anything else. Lets just imagine that your scary method worked on a silver coin but the one you were trying to clean was less than 100% silver so you only destroyed the part that was other metal. If it gives off smoke and sounds like a comedy routine, you are correct to be afraid. Your drachm is as close to pure silver as any ancient coin so it has a better chance of surviving your routine than most but the chances of your being happy with the results on your first try are far from 100%.

After you have tried this 'several' times, let us know how it went. Perhaps the correct amount is one drop or, perhaps, none at all.

It is not 100% certain that coins you buy that look good will not deteriorate because they were treated in some unknown manner by a previous owner but you have a better chance if you buy coins that look good as they are and leave the process to those who have done it several hundred times.

 

So distilled water it is. I have no experience using acids or chemicals in any way - so the mad scientist routine was never in the cards.

 

The bumps look like "horn silver" (AgCl). To my knowledge, nothing short of mechanical removal will get that off and mechanical abrasion is a risky proposition.

I googled "horn silver" to see if there is anything new and one of my coins is the in the Google preview . That Ptolemy I tet does have a light coating of horn silver but it is still a gorgeous coin.

 

I have recently experimented a bit with using a 10% solution of dinatrium-ethylendiamine-tetraacetate (Na2H2EDTA), a salt of ethylenediaminetetraacetic acid (EDTA), which is found in most soaps. EDTA is a chelating agent, i.e. it sequesters and binds metal ions into a complex. Thus, it will slowly eat away all (!) patina and encrustations which constitute metal compounds, including horn silver. It will neither react with the pure metal of the coin, nor, unfortunately, with non-metal compound encrustations such as chalk or most "dirt". Compared to cleaning with strong acids, lye, electrolysis, and other scary methods, EDTA could be considered a relatively mild approach.

A 10% solution in distilled water will be only slightly acidic (ph=5, about as acidic as your skin) and the substance is relatively harmless (used in most cosmetics). Therefore, you don't run the risk of poisoning your family when cleaning your coins that way...

That said, I agree with those who posted before me, and, would only use chemical cleaning methods like this as a very last resort on otherwise hopeless cases.

To give you an impression of both the good and the bad that EDTA can do, here are two before-and-after pictures.

I acquired this Alexandrian BI tetradrachm of Philipp II very cheaply because crucial parts of the portrait were obscured by horn silver. Here is the seller's picture:


After two days in EDTA, it looks like this. The horn silver is gone and the portrait now unobscured. Some copper-colored deposits remain, and though it might be possible to clean them off mechanically, I don't dare to do so. The EDTA also stripped the coin of all the rather pleasant darkish patina (silver sulfide?) and exposed previously hidden surface problems:


Did my cleaning improve or ruin the coin? You decide, I guess.

 

Looks like you may be on to something.

Does EDTA affect pure metallic copper, tin, or other metals commonly alloyed with silver?

John

 

I don't think so. EDTA works by "catching" and binding metal ions from metal compounds, and pure metals are not ionic.

With very sensitive metals, the weak acidity of EDTA might be a problem. I guess it's technically possible to neutralize it by using a buffer solution, but at pH 5, I don't really see the need for this when cleaning coins.

In practice, I have tried EDTA on silver, copper, billon, and bronze (the latter two without knowing the exact alloy) and didn't recognize it affecting the pure metal. No experiences with pure tin, nickel, or any other metals.

 

Isn't that an Antioch billon tetradrachma of Phillip II?

 

Yes, of course it is! I can't believe I wrote "Alexandrian" in my post...

Full identification:
Philip II, Roman Empire, provincial coin of Antioch, Syria, BI tetradrachm, 244–247 AD. Obv: MAΡ IOΥΛI ΦIΛIΠΠOΣ KEΣAΡ, bareheaded, draped, and cuirassed bust right. Rev: ΔHMAΡX EΞOΥΣIAΣ, eagle standing facing on palm branch, head left, with wings spread, holding wreath in beak, SC in exergue. 27mm, 12.52g. Ref: Prieur: A Type Corpus of the Syro-Phoenician Tetradrachms (2000), no. 332.

 

Where would one procure such a potion?

 

Since EDTA is used for complexometric titration, something that pretty much every larger chemical laboratory does, I assume that shops for lab supply, both brick-and-mortar and online, should have it. I bought 100g from a physical lab supply shop near me for about 4 dollars.

EDIT: Also, if you just search for "disodium EDTA" on ebay, you'll see a whole bunch of offers.

 

Thanks!

 

I have found household chemicals such as ammonia and white vinegar quite useful in cleaning ancient coins. They act fairly quickly and must be watched. The coin needs to be free of oils that might resist vinegar which I would recommend first. The coin can be immersed in vinegar or have it applied with a cotton swab for more control. The main advantage is that both chemicals reasonably safe.

 

The main thing to remember when cleani.... conserving coins it that always assume you cannot reverse yourself and go slow. Drachms are fairly small coins and not the easiest to handle. For example a technique I have used with coins the size of a US quarter or larger is to put the coin in a sink where the stream of water will hit it directly and then subject it to a stream of the hottest water your tap can deliver. I have used distilled (or deionized) water for a rinse, but not particularly to soak a coin in it. If you use a plastic net (like some fruit comes packaged in) to keep the coin from going down the drain (it HAS happened to me), this is something you can try with pretty much no danger of damage. Silver is tricky to clean, but not as tricky as copper coins (including bronze and brass).

I don't know about using EDTA, but I am a bit leery of it. The stuff with aluminum foil is OUT whether using sulfuric acid or sodium carbonate, I just don't trust it. There is a commercial dip that uses sulfuric acid and thiourea, but that is to strip toning and is most useful for uncirculated modern silver coins. Acetone can also be used to remove organic material and won't hurt the silver.

I have used lemon juice and it does a pretty good job, except your coin looks to have some zits of some sort.

Bottom line, if you want to do anything, soak for a day or so in tap water and then rinse with hot water having the coin protected from going down the drain. Try an overnight acetone (pure acetone and cover it to prevent evaporation) soak and repeat the hot tap water rinse. Pat dry. The only other thing you might like to try is some prodding of the encrustations with a sharp bamboo stick, but I leave that decision up to you. Whatever you do, go slowly, you can't go back.

 

Same question here: this tetradrachm from Syracuse is one of my headaches:

SICILY, Syracuse; Second Democracy (430-420 BC)
24 mm, 17.04 g; Ref.: Boehringer 675- 676
Obverse: Charioteer driving biga to right crowned by Nike flying right
Reverse: bust of Arethusa r., the patron nymph of Syracuse, whorl earring, and band wound four times around head and hair, ΣΥΡΑ{ΚΟ}ΣΙΟΝ, three dolphins, one behind the neck, two in front
It seems to have been burnt or is it horn silver ? on the obverse (or reverse ? some references say the biga is the obverse, others say it is the reverse, go figure).
Some of these issues also have these blackish something, e.g. http://www.forumancientcoins.com/gallery/displayimage.php?album=search&cat=0&pos=33
or even one at the British Museum, Museum number or reference 1938,0508.4

This is the one at the BM:


This is mine. Would you try to do something or just leave it as is? Your advice is most welcome

 

I have tried lemon juice and aluminum foil with success, but only in very short stints and then wash in distilled water. You could also spot treat areas with lemon juice on a Q tip, again rinse well. I would avoid soaking the whole coin in lemon juice if only one side needs encrustations removed. If you leave it too long you can get pitting. Again I say leave it alone.

 

Thank you very much Jay GT4 for your advice. Will leave it as is and stop worrying about it It is strange that some of these issues have the same black areas and always on the biga side