Toning

I'm not sure. You should ask an expert.

Nickels that tone?

It depends what the reaction is.

To each his own, but respectfully I disagree.. I don't consider toning to be damage at all, in fact I prefer to collect coins with attractive, colorful toning. Toning happens on top of the surface of the coin, it doesn't impare the coin itself at all. Also TPG'ers don't detract a technical grade from toning, they may bump it down for eye appeal if its disgusting toning. But likewise they may raise it for attractive toning.

Toning is a natural occurrence.. All metals tone due to elements occurring naturally in the air all around us. Unless you step in and intervene all coins will eventually tone. People who have silverware, flatware, copper bowls, silver vases etc all have silver polish because they know they will eventually tarnish/tone... Why would coins be any different? The only difference is its acceptable to clean silverware/flatware etc but unacceptable to clean coins. To me at least, dipping a coin (even safely) is what I would considered damage.

As for your question, eventually I'd say they may continue to tone, as by touching air there exposed to the needed elements for toning but it'll probably take a very long time though.

There are ways you could speed it up.. But there often frowned upon... Even though the elements causing the tone are the same as natural album/bag toning... your just putting them somewhere purposely to speed up/ensure the process.

But I don't feel like getting into a huge debate regarding toning/dipping, artificial/natural, acceptable/non-acceptable or the reasons why... Everyone has there own opinion and likes, and I won't tell anyone what those should be.

If you want them to keep toning keep storing them however you had them that caused it in the first place. 2x2s arent airtight but they are a form of protection. Anything that protects them for the most part will slow down the toning

Toning is the first stage of corrosion, the environment of Earth doing its best to turn your nice shiny piece of metal back into the copper and nickel ores from whence it came. Given enough time, it will eventually succeed in doing so. Since we as coin collectors collect coins and not pieces of metallic ore, it ought to be the mandate of every coin collector to attempt to prevent further corrosion, including toning, from happening to all our coins.

Toning happens on exposure to the air. Anything that reduces exposure to air will reduce the rate of toning. Putting the coin in a flip, airtite or 2x2 will all reduce toning.