At what point does toning become Verdigris? Back in the day when I started collecting, all toning was considered verdigris, but now they are popular. I know that chemically, it's just a phase in the process which can lead to a protective patina or permanent destruction. I ask because of the 64 Kennedy Thread with the ugly toning/verdigris in the devices.
Well, I think verdigris is a catch-all term for copper corrosion in the form of copper carbonate and/or copper chloride. It can be just a thin greenish coating up to severe encrustations. Afflicts coinage of pure copper and it's alloys such as bronze. In general, silver and gold alloys of 10% copper don't seem to develop verdigris as we are used to recognizing it in copper and bronze coinage. Toning is a term that for numismatists is used universally for all coin metals; copper, bronze, silver, gold, nickel. Toning can be very slight but can proceed to what is called "terminal toning" which is usually considered an end state as far as numismatic value is concerned. Chemically it is not an end state but most collectors usually find terminal toning undesireable. For silver coinage terminal toning usually makes the coin quite black. Below is a half dime of mine that is pretty close to achieving a terminal state on the obverse. Also, toning as we use the term does not include encrustations, blisters and similar severe disruptions of the surface but rather a thinnish tarnish on the surface of the coin. The type of corrosion that is toning will depend on the alloy metals and the environment that is causing it. Like silver sulfide where the corrosive element is sulfur in the coin's environment. If I've made any mis-statements, I'd be happy to be corrected.
It's interesting that I find dark field attractive on lower grade coins which create a sharp color contrast with the lighter design elements. Such contrast is lacking on some higher grade terminal toners. I guess it's a poor man's Cameo.
Called a "Circ-Cam" which you've probably seen many posts herein discussing. When a circ-cam has that lovely soft gray toning in the fields is when I find them most attractive. To my eye, that soft gray always looks velvety.
Verdigris and toning are two different things.well not really, but it sounded nice saying it. Hahaha. Verdigris is a reaction of copper and water moisture oxygen and contaminants. There's a decent write up and progression chart on it here: https://crescentcitycopper.com/why-does-copper-turn-green/ Toning, well that's early stage verdigris on copper, verdigris is "terminal toning" of copper. With silver, terminal toning is black, at that point it's a corrosive also it's a silver sulfide. A good chart of toning progression colors all the way to terminal is here: http://www.jhonecash.com/research/sunnywood_classification.asp In either case, copper or silver, toned coins can be pretty and it doesn't hurt anything until it gets to terminal. At that point it becomes a problem as silver sulfide or copper oxide both as a thick layer that includes sulfur, chlorides, and all the stuff that's bad found in air and water in micro particles that have built up over time. It's when it's terminal, whether copper or silver, the toning or patina becomes corrosion and can damage the surfaces and should then be "conserved" to remove this layer that has built up to a thickness that's reached problematic. As far as toning. Some like it, some don't. My opinion, for me it's a natural occurrence of copper or silver, and it's going to happen at some point given enough time and the right environmental conditions. Even if you notice it, it's usually got a really long way to go before it becomes a threat to the coin, and someone that hates toning may dip a coin multiple times and damage the surface trying to keep their coins white when they could have let it ride once it starts and wait for purple/black before conserving. Even then conserving can only be done so many times before it damages the surfaces. It's my understanding that it takes moisture and oxygen for toning to occur, and it take's a carbonate or sulfide to speed it up on its way towards terminal. It's my belief a coin would never tone if it were stored in a container and kept in nitrogen in place of oxygen or in a vacuum let's say, removing the oxygen. I know from pest control, if you have a pest problem, if you remove food or water, or break the life cycle, the pest problem is ended. You remove one of the links so they can't proliferate. I'd think the same applies to toning. What I know is I have 2000s silver proof sets all in their OGP bought from the mint. All have been stored in the same place under the same condition's yet one set has colored up drastically compared to the other 9 sets some are older most are newer. Why? It's got to be a conaminant in the mint packaging of that one set probably a sulfur compound in the packaging. What I'm saying is its not random, it's controllable and even possible to retard it. Many have had success with dessicant use to take up the humidity in their storage place, no moisture, no toning. So, at what point does toning become verdigris? "When the toning is terminal" is the simple answer. But it's a complicated question when it's thought about, and I hope I've taken some of the mystery out of it. Disclaimer: I'm a hobbyist not a professional or expert. By the way, Zinc rot isn't actually rot, and also totally controllable it's not a death sentence for a zincoln cent, just like seeing sign of toning isn't a death sentence either.
You were right to begin with John - toning and verdigris are completely different things. The thing the two have in common is that they are both forms of corrosion. But they are different forms of corrosion caused by different things. And no, toning is not early verdigris on copper. Copper can and quite often does go through the complete toning cycle from beginning to terminal - without verdigris ever forming on the coin ! That said, you can have toning and verdigris both on the same coin. And/or, you can have verdigris on a coin with no or very, very little toning at all. Here's the thing people don't seem to get. Verdigris is a very specific thing, in simplest terms it is what used to be copper. In other words the former copper molecules turn into verdigris. Verdigris the material that results from a specific type of corrosion. Think of it like this, verdigris is to copper what rust is to iron and steel. And verdigris can also occur on just about any coin. It occurs on copper coins, silver coins, gold coins, and even nickels. But that is because pretty much all of these coins have some copper in them. As to the original question - Never, they are merely different forms of corrosion. Copper is kind of unique in that regard. Verdigris is a green powdery substance, it can turn hard and crusty over time, but when it initially forms it's powdery in form. Toning on the other hand is completely different. It can on occasion be virtually any color, but it is never a powdery green substance. And toning and verdigris can both literally "eat" the copper leaving behind pits in the surface. So while toning and verdigris haver some similarities they are definitely not the same thing, nor does one ever turn into the other.
for Doug-- I've read many posts here and they haven't specifically answered some concerns I have. Maybe I'm dense. I think on one post you noted that verdigris on one coin can't cause copper corrosion on another coin. What causes corrosion is the air and water. This implies to me that it is all right to keep coins with verdigris in the same storage area as coins without verdigris, i.e. old coppers in their cotton sleeve and 2X2 envelope can be kept in the same red box (or similar) form of storage. Based on one of your posts I've transferred all my copper coins into appropriate plastic bags and then these go into a larger Rubbermaid container with desiccant and I keep the humidity below 20%. Thanks for your input on all these discussions. Sometimes everything seems to go around and around in my head.
If there is ever something you don't understand or you have questions - feel free to ask and I'll do my best to answer.
That is still one beautiful half dime. I'd love to see your full collection of half dimes, if ever you want to undertake the effort of posting photos of your full collection on CT. The ones you have posted on various threads have blown me away - super high quality.
Incorrect, verdigris from one coin can provide the feed materials to start corrosion on another. I found a great example of this in a roll of Lincolns where a very corroded cent was contacting a full red one. Coins with verdigris should always be segregated from coins without it!
Thanks! The eight or nine coins I have (with mild verdigris) are now in their own box with dessicant. The Verdi-Care has worked exactly as you mentioned. It stopped some very light verdigris that was starting and those coins with small spots appear to be sealed. Everything is stored below 20% humidity. From all the photos in the Verdi-Care instructions have given me a pretty good understanding of the coins where VC will be most helpful.
Just for the sake of clarity Thad, and so all readers understand your comments correctly, I'm going to add this. For verdigris to be transferred from one coin to another it requires direct, coin to coin contact - with no barriers of any kind in between the coins. As long as a coin with verdigris on it is in its own flip, 2x2, or other hard plastic coin holder like Air-Tite or slab type holders - that coin is adequately "segregated" from other coins, and it cannot cause other coins to also get verdigris on them. And yes, as long as the coins with verdigris are all in their own individual coin holder it is perfectly safe to keep them all in the same coin box, 2x2 box, slab box, or other storage container with coin that have no verdigris on them.
Doug, Would a Large Cent with a small amount of Verdigris--placed in a cotton sleeve and then put into an old-fashioned 2X2 envelope be considered safe to keep with coins without verdigris in similar envelopes? I know many collectors do this--but obviously this system is not "air tight"--is the cotton and paper envelope enough barrier? (Maybe there is no clear answer to this?) Sorry to belabor this, I want to do my best to preserve the coins.....
Well, cotton sleeves and paper envelopes are certainly not a desirable storage method for coins as they'll cause hairlines and lead to excessive toning. But yeah, they'll do the job you're asking about.
