Yes, what can one do with coins with huge amount of crust on them, let's say hardened crust from digging. Let's imagine if it can be possibly a slightly uncommon coin, so harsh cleaning is not an option.

What are the choices?

For a dig coin options are limited. Olive oil, a soft bristle toothbrush and a lot of patience are a good way to go.

Olive oil, maybe just a long soak in distilled water can help...I use both for my old uncleaned romans... with soft brush scrubs using a mild dish soap you might get it off.

Even with coins that are not minted in copper? Sorry but I had terrible experiences with olive oil.

If they are not copper I use distilled water (with repeated soap and soft scrubs). I only use olive oil with copper, brass, bronze...that is just how I do it, I have never been told that olive oil cant be used...Its just that I have never had a seriously crusty silver or nickel coin that needed anything more than a soak to get a little lite crust off.

I start with water, the soap and water brished with a toothbrush.
After that it depends on what the coin looks like.
Brass brush, a mild acid like olive oil, careful picking, or just a lot more soaking in water/soap may be in order.

To have it professionally conserved ? I know of nothing else that would do it and yet not qualify as harsh cleaning.

a soak in distilled water and a light scrubbing is not harsh cleaning for an old dirty coin that has been buried long enough to be encrusted...I would save the money sending to be 'professionally' cleaned...if you are carefull, nothing they do will be any better or worse than what you can do yourself...much like grading a coin...it is nothing you cant do yourself or with the help of other knowledgable collectors...if you dont want to spend the time, thats fine...but I prefer to save the money and do it myself instead of allowing someone to eek a bit more profit from me for a hobby.

If it is REAL crusty (chunks of crust) after a soak in distilled water and a quick soak in soap and hot water the chunks of crust might soften a bit and you might be able to pick off the chunks with a dental pick...be very carefull not to scratch the surface...if it doesnt chip off, dont force it very hard...just let it soak more.

I should add that this my opinion only...a coin that has sat in the ground 100-2000 years is not going to be damaged by water and a little soap and I would rather have a nice toned or nice patina without dirt and crust on it and I see no need to shell out money for someone else to do what I can do just as well on my own...

Concentrated Nitric Acid followed by Hydrochloric Acid.
In reality try Acetone. Nothing special, just Walmart or Kmart off the shelf Acetone. Brief soaking, rince with distilled water and blow dry with a hair dryer. Remember that crust of any kind formed on a coin is usually, but not always, a compound of the coins metal and some outside agent. This means as you remove the crust you will probably be removing some of the coins metal. This is why so many say never clean a coin.

After a study of metal and the reactive properties of each, I would say the above is true only in certian cases...silver and gold are very non-reactive thus with these 2 metals, they react FAR less with most substances than any other and are very NON-corrosive thus silver and gold coin surfaces do not react much (of course there are exceptions) to what touches their surface the way say...bronze, brass and copper do.

Use HF... don't use gloves with it.






It'll eat through to your bones.

I was probably thinking about the lines of baking coins since the expansion and contraction of the metal in the coins versus the crust would vary, although this is just an idea that I see in the kitchen.

When you have burnt organic compounds on a wok, pan, etc, you would try to soak it first for quite some time and later evaporate it with extreme temperature and suprisingly the crust come off cleanly as it cracks up.

Perhaps it's just a silly idea but you know, pots, woks, pans, etc are all metallic - aren't coins metallic too? I'm not too sure what the crusty layer that cover various different type of coins could be, but I guess I will try that experiment one day when I got the time.

I have done that with crusty ancients to some degree of success.

My friend who has little patience puts them in an electrolysis aparatus
Half of them came out nicely

He did not say what the other half looked like

without patina, pitted and nasty I would think from my experience of doing the same with old copper roman coins...though if you give them just a quick shock in water you might be able to get it and still save a patina. I would say this is the very last resort.

Pitted and nasty in MS 64

Can somebody teach them how to grade


http://cgi.ebay.de/1922-20-Gold-NNC-MS-64-...1QQcmdZViewItem

Not really. Silver is very reactive with a multitude of agents. Note the outer ring of electrons is only 1 making it very receptive to additional elements with sharable valences. Note also Silver is much higher of an electrical conductor than even Copper but is not utilized as frequetly due to cost and tarnishability. Silver will react with Oxigen, Florine, Chlorine, Nitrates, Sulfates, Iodides and on and on and on. Note people with true Silver ware for household kitchen usage spen numerous hours removing the Oxide from Silver.
All as noted in my collection of chem books.

Silver is highly resistant to oxidation, more than copper, brass and bronze. What tarnishes silver is a reaction to Sulphur in the air and soil. Let me also say that I did not say they (gold and silver) were NOT reactive, I said they are far LESS reactive to a variety of elements than others such as copper, Bronze, or Brass...bury a silver or gold coin or leave it in a room for a thousand years, then do the same with a copper coin....Gold will not tarnish or react on the whole, silver will have tarnish but not much else unless exposed to more extreme atmospheres, while the others will completely coated in a patina which is a reaction of the surface of the metal to many different elements in the air and soil because they are MUCH MORE reactive. This is simply fact....A gold and silver coin will weather the years much better because it is simply less reactive to less elements that normaly occur than other metals commonly used.

Now if you are refering the reactivity of silver in chemistry projects or photography, thats another story...I was speaking of exposure of silver and gold and their reaction to soil and air as compared to metals such as copper...not all the chemicals it will react to in a lab...there are numerous that I could list but wouldnt be relevent to this thread having to do with coins.

Chemically, silver is not very active — it does not react with oxygen or water at ordinary temperatures, so does not easily form a silver oxide. However, the other metal in the alloy, usually copper, may react with oxygen in the air.

Exposure to SULPHUR will cause silver sulfide (Ag2S)

Sodium Chloride (NaCl) or common table salt is known to corrode silver-copper alloy, typically seen in silver salt shakers where corrosion appears around the holes in the top.

These are the only real problems silver will have in common conditions and tempuratures.