In addition, I actually used this knowledge to improve this coin: A series N type 41b sceatta, which was heavily overcleaned. Note the scratches on both the obverse and reverse, and shiny, polished higher points. Also note that a small remainder of the deposits is still present (e.g. obv between 7-9 o clock; small black spots between the figures). Immersing the coin in sodium thiosulphate dissolved most silver chlorides. The Na3AgS2O32 then filled the micro-scatches, which are now only visible by magnification (this coin is 11 mm) and not by the naked eye.
Look at @sand coin in post number two. See how its toned in front of the face? Also notice how the toned area is lustrous, (shiny)? That is the original melted silver when struck. It makes sense the last remaining on this coin is in recessed, protected areas, which is always the last to lose the luster. That is toning that is natural, since it is only occuring on the correct area of the coin. On a AT coin, it can force "toning" on the higher areas where the luster is clearly gone. However, the color will make it harder to see its not lustrous, unless in person. Now, can you AT a lustrous coin? Yeah, and I even know how to do it so you cannot tell its not "natural", but why? Its the luster that should be desired. Once a lustrous coin is toned, to remove it you have to remove a layer of the luster. That is why I tell people to value and appreciate lustrous coins, and not care if its toned or not, its the luster that is desirable.
Good writeup. You are right, almost any sulfur source except for paper is "too much", and the sulfur reacts too violently and therefore not as attractive. There is an even better source than paper envelopes, but I am stopping the conversation there. I was taught by old time dealers about 40 years ago. I am sure the knowledge exists, but I refuse to spread it on the internet, since I am against toning on purpose for any reason.
I agree. Surely whether toning is viewed as acceptable or not should not rely on the "intent" of the toning. Toning is toning, and is a result of a chemical reaction. If it comes down to the intent of the owner, it would result in ridiculous situations like a coin kept in a cabinet for safe keeping 100 years ago being acceptable, but not a coin that was intentionally put into a cabinet to tone - which would be unacceptable. Exact same process, but the intent of the action was different. I say, be like Elsa and let it go. Who cares. Let the toning be toning.
Exactly what I was thinking. It's a bit silly how the coin community in general dictates what is NT and AT based on the coin owner's intent.