Toning progresses in stages, the darker it is the more advanced the stage. Once it has turned black it has reached the point that it is corroding the coin, eating into the surface of the coin. And if that black toning is removed the damage from the corrosion is visible on the coin. However, in the earlier stages of toning, if the toning were removed, there is no visible damage to the surface of the coin. That is the difference.
I believe you, but I'm still somehow skeptical. Mostly because I have never seen one in this "terminal state," despite having seen quite a few coins with century-old pedigrees. I have a hunch that we both believe the same thing, but are using different terms to describe it.
Hello Detecto, I don't have experience with the wooden slab boxes. I do use these depicted products for slabs. I recommend using them. The eagle plastic pages hold 9 coins per page. I place them in 1/2" 3-ring binders so that two pages may be displayed when the book is open. That equates to 18 coins that you can simultaneously view. The Lighthouse wooden boxes provide a first class presentation & they fit the same space as the 1/2" 3-ring binders. However, they make it difficult to view both sides of the coin & only fit 8 coins vs 18. For long term archival storage of slabs, I just shrink-wrap stacks of 24-25 coins. The shrink wrapped stacks of 25 are smaller than the blue 20-coin PCGS box. This can become important to conserve space in your SDBs.
There have been many examples posted over the years. Here's one that has some toning that has reached its terminal stage, or right next to it - http://www.cointalk.com/t221950/
If you use vinyl binders, be sure to use the " PVC Free" ones. If you have wood display holders, and want to use them, your choice, just take notice if any changes start to occur. A coin isn't going to self-destruct in a short time unless it is in an environment you should not be in either.
I guess that technically, it is called stretch-wrap. Here is a link at U-Line: http://www.uline.com/Grp_92/Mini-Stretch-Wrap-Rolls I probably used the term "shrink-wrap" in error. Shrink-wrap tends to require heat to shrink.
Bill, for silver is matte black that you are looking for. Toning will go to black, but if its glossy then most likely, (but not for sure), you can dip it off. However, once its a matte black appearance, then 99% its corrosion damage on the coin surfaces. About 2.5 years ago someone posted a link to "gorgeous toned Peace dollars" on a website. I looked at them, and at least half were corroded, the toning gone too far. There is a distinct REASON use old collectors used to prefer white coins, even if dipped. There is no easy way to see what is under the toning, either tooling, corrosion, etc. People who buy toned coins do so at their own risk, ESPECIALLY if that toning is very dark.
I'll expose my ignorance: Is there a problem with vacuum-packaging (FoodSaver/Tillia) for long-term bulk storage...slabbed or not? I've got some (modern) gold in such a pack, but gold isn't as susceptible to degradation as silver, and the next major batch WILL be silver...so I'm considering suckin' 'em, for ease of handling. Bad Idea?
The thing is, I have seen a good number of old "cabinet" coins, and I have not seen a black patina with corrosion on any of those. A question for Desertgem - when the surfaces of a coin tone completely to black, does it become chemically stable?
Cabinets usually do not have as much moisture around to let it go that far, but it can happen. I have seen some from the SE that were bad, but I believe the cabinet had been moved to a basement since the cabinet was in rough shape too. As for black being stable, my opinion would be no. It goes from glossy black to matte black, and the corrosion continues until theoretically the coin is completely corroded and all natural silver is converted. Stable toning can only exist if you have taken away the precipitating toning agents. Like others point out, wood will naturally over time lower its emissions, so in a cabinet it can start out badly for the coin, but get better over time. Put that same cabinet in a high moisture situation, though, and the coins will continue to deteriorate.