“Rainbow” toning or patina is an optical effect caused by graduated layers of silver oxide on the surface of a coin. This is often seen on coins that have been in contact with a sulfur source (a great oxidizer) for a good number of years (usually 20 years or more).
Why are some Morgan silver dollars rainbow toned?
Toning Propensity of Metals When first minted, copper coins have a bright red color. Over time, the copper oxidizes and the coin’s color darkens to brown. Silver frequently reacts with sulfur to form rainbow toning – the Morgan dollars at the top of the article are examples of that process.
Why do some pennies look rainbow?
How Does a Coin Get Rainbow Toning? When trace amounts of sulfur or other chemicals come in contact with the surfaces of a silver coin over a period of years, the color and appearance of its surfaces will begin to slowly change.
How can you tell fake coin toning?
Signs that a Coin Has Been Artificially Toned
- Hairline scratches on the coin’s surface can indicate cleaning with an abrasive chemical or brush.
- A dark brown or bluish hue often comes from chemical toning.
- Spots often appear on an artificially toned coin’s surface if the chemical reacts unevenly.
Does toning affect coin value?
Different colors and patterns of toning can have varying effects on a coin’s grade and value. For example, brown spotty toning could decrease a coin’s value, while colorful rainbow toning could increase it. Toning patterns may cover an entire coin, just one side, or just one area.
Why does a silver dollar have a rainbow color?
The chemicals in the cotton that was used to make the canvas bags reacted slowly over time and resulted in some beautifully rainbow toned silver dollars. Additionally, certain coin folders, albums , and paper envelopes that are not made out of archival quality material can contain sulfur and acids that will react with a coin’s surface.
Is there a way to tone a silver dollar?
Some collectors pay a premium for beautifully toned coins. Usually, it’s the people who collect old silver dollars. Beauty is in the eye of the beholder, as some like certain colors or perhaps a rainbow effect, whereas others prefer the toning to be only around the edges.
What causes Rainbow Toning on a silver coin?
“Rainbow” toning or patina is an optical effect caused by graduated layers of silver oxide on the surface of a coin.
Why are silver coins toned more than untoned coins?
Naturally toned coins can bring a premium several times more than an untoned coin. Many of these silver coins toned as a result of the way they were stored for a long period of time. Some Morgan dollars sat for over 100 years in canvas bags in the United States Treasury’s vaults.
