Glenn B. asks: What is meant by the term “re-colored” as used by some of the grading firms? Thanks.
Toning is natural on metals such as silver and copper. Re-coloring refers to applying an artificial patina to a coin. Silver, nickel and copper are chemically active and will oxidize to different colors depending on the depth of penetration of the metal. This happens when a coin is exposed to an active chemical such as sulfur, often used in the manufacture of paper, cardboard and canvas bags. The patina usually takes a great deal of time to develop, anywhere from a decade to centuries. Collectors often prize toned coins for their aesthetic appeal. (See: Why are toned coins so much more expensive?)
Artificial toning is often applied in order to cover up some flaw on the coins surface. The flaw could be an area that has been repaired, scratched or cleaned. The patina appears shallow in depth and often shows sudden changes of color to the surface instead of a smooth transition, especially if the coin has been exposed to high temperatures. In some cases, toning has been applied to deceptively inflate the desirability of the coin to those unfamiliar with the “look” of natural toning.
The technique for applying artificial toning often begins with stripping the coin of all oxide. Removing patina with a mild acid that is in such products as Jewel Luster also removes the oxide layer. This process removes metal and therefore reduces the amount of luster that is usually present on a uncirculated coin. The luster of a coin, the effect that causes light shined on a coin to move in a circle, is caused by flow lines created when a coin is struck. When you dip a coin, you are also removing the flow lines and thus the luster as well. Sometimes no more than two dippings will turn your uncirculated coin into one that is AU. This factor is one of the diagnostics that are used to identify “re-colored coins”.