Causes Of Verdigris On Copper.

Well, that's why I deferred; I've no expertise with the formative stages of verdigris and if it's that liquid in the early stages I'd never know. I *can* say that damage from PVC outgassing would never proceed that quickly, so you probably got it right for the coins.

I got virdigris on a 1934 German (Nazi) Reichstag clad coin. It appeared only in high relief areas. My best guess is that it was a combination of storing in a PVC plastic holder and moisture. I experimented a little and soaked the coin in 100% Acetone for 3 days and the green wiped off with light tamping from a couple of Q-tips.

Here is my definition of verdigris I wrote for my book and Wikipedia:

Verdigris is a variable chemical mixture of compounds, complexes and water. The primary components are copper salts of acetate, carbonate, chloride, formate, hydroxide and sulfate. The secondary components are other metallic salts, acids (organic and mineral), atmospheric gases and water. All the components are in an ever-changing and extremely sophisticated electrochemical reaction equilibrium that is dependent on the ambient environment.

I have soaked coins in alcohol but think it is best not to do it for more than 30 seconds. I have used acetone on coppers in the dark because it will react in the light I read. For those coins that are worth a little more, I only used distilled water before applying Verdi-care to them. Fortunately the green stuff came off just by rotating it on a cloth with Verdi-care on it. Maybe acetone in the dark is better than alcohol? I just heard soaking coins in alcohol from the forum admin from About.com. I find it removes crud rather quickly. If it was PVC though acetone is good for that but if not done right it can discolor coppers I heard.

I've used Acetone on Copper coins in a jar in the Sun, in the shade, in total darkness. If you find someone that says the Sun and Acetone will change Copper, it may well be they used a different Sun than I did.
Exactly what color was the contamination on your coins. If it was greenish in color, it is the reaction of Sulfur Acids in the air. If you see or know anyone with Copper pipping in their homes and it goes into the house, you may also see that same green color to their Copper Pipes. In many areas the burning of Sulfur rich coal emitted Sulfur Oxide into the air and when that mixes with the moisture in the air, it becomes an Acid. You may have heard of damage to statues and other outdoor items from what has been called Acid Rain. That is the rain that goes through the Sulfur Oxided Air and becomes an acid.
On many coins, if left exposed to this, they usually turn green. That is the remains of Copper Sulfate or Copper Sulfite. However, on coins it now has become part of the coin and when you remove it, your also remove part of the coin's metal. Slight, but part of the coin is now gone.
The stickyness you explained could be almost anything that was in that container or what the container was made of.
As already noted Alcohol is not a good thing for cleaning coins. That paper box may well have had Sulfur in the paper mixture. Regardless, get all those coins away from that box.

You are right, the stickiness could be anything. I was told that alcohol doesn't affect coins, I will have to Google that. I only soaked them in alcohol for 30 seconds since it does remove tape residue if that was what it was. I probably should have just left them in acetone for a little while and that is all. I always give a distilled water rinse after soaking in anything. People have told me several times that acetone can discolor coppers I personally haven't had an issue but people swear it will discolor coppers. Distilled water is always the safest. I had a 1874 with some green stuff on it, that one I just soaked in distilled water and applied Verdi-care and that is all.

Yes, I took the coins out of the jewelry box. I have coin envelopes and mylar flips.

All-
I can't add much about the causes/cures of verdigris, though I can speak to using ethyl alcohol to "clean" coins: don't! At least not copper, bronze, or aluminum-bronze coins- it will alter the patina by turning the coin various shades of purple (due to formation of copper oxides and sulphates, I believe). While the "purple haze" finish is interesting looking, even pretty, the coins stand out like a sore thumb and yell "cleaned!". Copper-nickel coins seemed to do fine, though you have to beware of residues from evaporation(unless you use laboratory grade 100% EtOH, which I doubt you would). Of course you can get rid of the residue by rubbing the coin with a cloth. Of course rubbing the coin with a cloth adds unnatural lustrous highlights to the raised parts of the design. Of course unnatural highlights yell "cleaned", so maybe not using alcohol at all is the best idea...

cheers,
tbg

I realize this thread is old, but acetone will not react with metals, whether in the dark or under bright lighting. It won't even remove tarnish. But it will quickly and completely dissolve PVC (and most every other petroleum based plastic). I have safely used it on several coins in my registry set. It evaporates very quickly, and it is important to avoid breathing any fumes. I suggest using it in a glass covered dish. Personally, I use a glass covered butter dish, and a use a can of compressed air to blow off the still liquid acetone when I remove coins from the soak, as any dissolved PVC will be left behind on the coin after the acetone evaporates. I can provide several examples where heavy PVC residue, (which was green and gooey in the crevasses, but hazy elsewhere), was completely removed and made it through PCGS certification to be part of my Registry Set, so I speak from experience.

Verdigris on the other hand, is a tougher nut to crack, and most people don't have the time o patience to leave a coin in mineral oil or Refined (lowest acidity) Olive Oil for 6 months or longer to soften it for easier removal. However, I am currently experimenting with a process (based upon procedures I have used at work to perform accelerated life testing) to see if the 6 plus month time frame can be significantly shortened without unnaturally affecting toning of bronzes. If it substantially improves the appearance of the coin without producing unnatural toning, I'll post the process with before and after pictures.