Verdigris and gold and silver

Took the thought right out of my head w/o all the chemistry that was not in my head - so thanks.

 

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In my very limited experience, powdery deposits on silver are sort of rare. The one's I've seen have been associated with corrosion or PVC products. I have never heard anyone refer to the corrosion products on silver as "verdigris."

 

That's great advice and thanks; however, did you happen to read that he has cleaned so many coins already that he is tired of doing it?

I know a telemarketer who would open original rolls of silver coins and dump them in a bucket of sudsy ammonia (plus the rainbow toned end coins) to make them "bright" as they sold better on TV that way.

 

Most of the "green" residue on gold occurs in lumps over a oxidized copper spot. However, most of the time it has transferred/adhered to the surface from the container it was stored in. The green deposits that are found on the brass snaps of an old leather product are similar.

 

Conservation professionals I have spoken with DO NOT call this product "verdigris." See post above. That will come off your coin very easily. The method ("spot conservation") involves a toothpick and a stereo microscope. When you know how to use the toothpick correctly (don't push it around) you will not scratch the coin or leave ANY evidence of the conservation.

Note: A Q-tip with acetone will also remove it; however, that "typically rookie method" will remove any skin that is on the rest of the coin. SO DON'T DO IT.

 

Whatever it is, I'm returning it since I bought it for Numismatic reasons.

 

That will come right off. Nevertheless, ask the seller for the weight and specific gravity.

This was answered by Doug.

If you look in the center of the discoloration you'll see a raised lump of "the something" he mentions. The discoloration will come off. If "the something" has etched the coin's surface there will be tiny dull spots in the surface.

 

Dang...Spock started this 5 years ago...

 

I never look. Someone asked a question yesterday and I thought the thread was current.

 

Oh, I like old posts, just noticed how old this one was.

 

OLD POST'S NEVER DIE nor either fade away...

I posted earlier that this type of green residue on gold is not considered verdigris. It is very easy to remove when it is not hard and crusty covering a dark spot on the coin.

The bottom photo show a similar residue on a gold coin. Near the rim over the top of the "A" you'll see some green debris. Right next to it is a dark black spot. The middle photo shows the pointed tip of a wooden toothpick I'll use to "push" away the debris. The top photo is the finished job.

These are the important points I wish to make:

1. The green on the Indian is similar and from the same cause; however it is more "liquid" than the green I removed which is dry and soft. Both come off very easily.

2. The black spot on the coin will come off too using a different method. It is debris struck into the surface. Very often, this type of spot will be covered with a tiny green residue.

3. When copper is near the coin's surface, it produces a brownish red stain around the spot. These stains can be associated with the same type of hard/soft green residue.

If one of our chemists wishes to post the chemistry of spotting on gold and the types of dry or liquid green residues, please chime in! Otherwise, it is probably on the Internet.