Tones on Silver and Copper: Need help from chemists!

[ALPHABiT]

Hi friends,
as many of you know, i collect coins too. Expecially in Gold and Silver ( ) .
There are few questions i would like to ask you chmistery experts about oxidations on metal alloys that no numismatic-experts was able to exactly explain to me. And i'm sure u'll do .

I'm going to show you some coins with different toning types on surfaces, i would like to know what kind of chimical reaction it was and if possible how to "remove" it from coin without loose any coin parts
and/or how to reproduce that tones on other not-toned coins!

Thanx for your help!

 

[ALPHABiT]

Rainbow on Silver coin:

 

[ALPHABiT]

Green on Silver

 

[ALPHABiT]

Black and "white" on Silver

 

[ALPHABiT]

And at least, Copper turned RED!

 

[jimdoc]

Most of that would be referred to as toning.
Most collecters like that, and cleaning it off
would make it a cleaned coin. It is better to
leave the coins in an uncleaned state, unless
you get really crudded up coins by metal detecting.
Cleaning coins almost always decreases the value.
So it is better left to the buyer when you intend
to sell, let them decrease the value after they
buy it. Jim

 

[ALPHABiT]

Thanx Jim, your suggests are right.
But i'm an old collector enough to know those basic rules.
Many coin sellers clean and re-make ossidations on coins. No PGS or other can recognize that, of course.
I'm just couriouse to test my self how to do that, if someone here can help.

 

[butcher]

just a thought of mine what about using a gas of acids, since most corrosion is probably from the gases, over time, and maybe buffing fine cloth? maybe try on junk stuff ?

 

[Lou]

The oxidation on the dime is from mixtures of oxides of various thicknesses formed over time.

The green on the silver coin is probably a copper patina (most likely copper carbonate).

The black on the silver is most likely silver sulfide.

The red on the copper is indicative of it having undergone a chemical cleaning leaving a thin film of CuO. I have achieved that effect numerous times on copper strips-- a simple dip in hydrochloric acid, then rinse in distilled water will give you that.

Lou

 

[ALPHABiT]

Lou, thanx.
Green is probably copper patina, yes. But it seems it cant be removed without removing part of coin with chimical too.

I'm afraid to use Copper in HCL 'cose i think it would corrose a bit coins. Not so important on circulated ones, but it can be really a loss value on uncirculated. I will trinse some rines on some low values...

Black oxidation on silver is simply removable without damage the coin surface and removing nothing with a very low electrolysis (simply using hot water + alluminium) or just using wave cleaners for jewelers.

Rainobow patinas are interesting. I'm going to suppose it can be done using some NH3 on silver.

 

[ALPHABiT]

For Expample...
What is contained in this ? http://www.microstampusa.com/winox.html