Cleaning Ancient silver coins

[bruce61813]

Sometimes you find Roman or other ancient silver coins with a crust of black silver sulfide. This is very hard and difficult to remove. One odd method that I have found, is actually a combination of two other methods.

Take 8 ounces [350 ml] of oliver oil [it does not matter what type, that's why I keep some around that has become rancid, it works fine for coins, thay don't care about the taste!], add 1 tablespoon of lemon juice, mix completely. Add the coin, and heat [I use the the hot plate of a cheap coffee maker] you only need to heat it to a temperature of 150 deg. F [62 to 65 deg C ]. Let it sit for 30 minutes. the oil will become clear and you should see most of the 'crud' has been removed form the coin.

this would very well for solid good silver. With debased coins, it will depend on the amount of copper to silver and the corrosion. I do not recommend it for Fouree's, as the corrosion will often run under the silver/copper interface, and the silver layer may break free.

Bruce

[Samuel Tan]

Bruce,
I have some silver coins, I assumed it was in a roll. The face is as good as un-circulated, but 25% of them have ugly Dark Green crust on their surface. I know it did not eat the surface, since I removed the worse one with chemical dip. I don't want to ruin their value, but I think, I will increase it if I can remove the crust. Should I leave them or should I follow your suggestion without degrading their value. They were 1926 to 1937 coins.
I could scan them next week, I hope.
Samuel Tan

[bruce61813]

Samuel, hello and welcome to the group.

To be real honest, I don't deal with 'modern' coins. the coins I deal with, when I deal with them are from the ancient Roman and and ancient Greek eras. Your 'green' comes from the copper mixed into the silver alloy to harden it. It you have one coin that you want to try, I would suggest the olive oil bath. thie works very well on ancient silver. Take 4 ounces [about 350 ml] of olive oil, add 15 ml [about 1 ounce] lemon juice, mix them together, it will be an opaque mix, add the coin, and place somewhere warm. I use an old coffee maker hot plate, let it sit for about 20 to 30 minutes, or until the mixture becomes transparent. The lemon will only effect the copper oxide, not the silver, and the oxide will be floated off by the oil. This has worked well in the past, you coin will not be bright and shin, but may have a slight 'mat' silver color. This would look like normal age, or natural toning, without any chemical additions. If I can find a 'new' coin , I will try it and post pictures.

Bruce

[Samuel Tan]

Bruce,
Thank you for your advise. I tried on two of my worse coins, it works, but most "oxidation" still left on them.
I like the natural mat look.

My questions:
Is simmering good enough, or should I buy a used coffee maker for lower heat?
Can I heat them longer to remove them all?
Since the oxidation is very stubborn, can I add more Citrus?
Please advise me.
Thank you,
Samuel Tan

[bruce61813]

It would be good if you could post a picture of the coins, it helps to see what they look like. I would get a coffee maker, as its hot plate keeps the liquid at about 150 degrees F, and that is fine. I don't think I would add more citrus, but you may try a bnew batch.

Bruce

[Samuel Tan]

Too bad, I can't post a picture. I tried before, but for any reason it never work.
My email is samueltanh@gmail.com, if you don't mind to respond to me, I could send you the pictures right away. It will be great if this works, I have many Unc. Coins with this kind of blemish. I would like to remove the majority of oxidation only, not totally cleaned.
When the Japanese conquered Indonesia, they confiscate everything has some value, including Metal Fences and Used Tires. People start burying their jewelry and coins in the yards. After the Japanese surrender, they dig them up and sell. But some of them forgot where they buried them or past away, after a while people recovered and sell them.
Samuel Tan

[bruce61813]

Samuel, I received your pictures. I would treat them with the oil & lemon juice again, they look to have been badly corroded.

Bruce