Huge Premiums For Toned Morgans. How Stable Is Toning?

It is not oxidation. Silver oxide is gray and produces haze. It is silver sulfide, so the removal of the coin from an environment where it has sulfur exposure should halt the toning development. Coins in plastic holders should be stable in color.

Thanks, Andrew99. So does anyone know if these plastic TPG slabs are air-tight, protecting the coins from sulfur in the atmosphere?

You can generate toned coins, completely naturally. It just takes 10 years or so. However, if I can turn an $80 coin into a $3000 coin, its worth the investment.

Toning is an endlessly debated subject. Certainly today's slabs virtually halt the process, especially on silver, which is the key point. Most all uncirculated silver coins prior to the 1930s will (and should) show at least some faint sense of toning if they have not been "dipped", especially around the edges - the first place to look on a so-called "blast white" coin. Problem is, the TPGs will slab dipped coins anyway, so many series (SLQs, Mercs, etc) are often collected ONLY in white, which is ridiculous.

If you collect high-end silver tyoe, expect a degree of toning and decide on a case-by-case basis.

Just my opinion.

It makes sense to protect your premium toned coins to the extent possible. Slabs are a good start but as noted they are not air tight. The coins should be further protected by storage in a cool and dry closed environment like a safe or safe-deposit box. Invest in a couple of silica gel desiccant packs to keep in the safe and make sure they are reactivated periodically. These precautions should maintain the existing tone indefinitely.

Not all metallurgical reactions require the presence of oxygen or other components of room air such as nitrogen; some reactions can even take place in a vacuum.

Since keeping your coins in a vacuum is impractical, the best way is to keep them in a controlled-humidity environment, with filtered air, and minimal exposure to light, in sonically-sealed plastic slabs. The surfaces should be completely rinsed with a solvent such as pure acetone and then blown dry with micron-filtered, dehumidified compressed air prior to encasement.

Intercept Shield holders are also good way to protect your coins / or Dansco's version of the same slipcase for their albums.

I can see that. Sulfur is a byproduct of natural gas combustion (in the form of sulfur dioxide) and also used in small amounts as an odorant / detectant along with mercaptans and thiols; given sulfur's reactions with silver coins it is likely. But here, most natural gas is processed (to protect the integrity of the transport piping), and has a very low sulfur portion. This may not be the case in Canada or in some very rural areas where field gas is used instead of pipeline gas. Most modern, efficient furnaces, almost all of the combustion gases should be exhausted through the flue and via the air exchange - flue tubes. If there's a cracked HX/sooted burner/etc the higher levels of CO2 and resulting health risk would be a much bigger issue than the toning of some silver coins...

No need to do that. If you use the search tab on this forum for toning, you will find many, many faster methods to tone a coin.