New collectors and the general public need to understand that nowadays serious collectors prize coins that haveoriginal surfaces and avoid those whose surfaces have been damaged by "cleaning". Those who think they should "shine up" their coins are likely destroying much of whatever market value the coins would otherwise have had.I'll repeat what I wrote recently on another thread on the same subject:
The term "cleaning" is itself a misnomer because a process that solely removes surface dirt from a coin without affecting the surface of the coin--literal cleaning, such as by using a solvent such as acetone--is not included in this term. Instead, "cleaning" in its negative numismatic context means a variety ofchemical and abrasive processes that chemically or physically alter the surface of the coin itself,resulting in an unnatural or unattractive appearance. This includesa number of different appearances,such as the following:
1. Heavy hairlining from abrasive processes such as by scrubbing the coin even with a cloth or rubbing it with a pencil eraser or the like. To the naked eye, this includes an unnatural "whiteness" that appears at different angles as the coin is rotated in the light and an unnatural, unattractive grey color in the abraded areas that is unlike the natural, darker or brownish greys of unimpaired circulated or toned coins.
2. Blotchiness or unnatural brightness, shininess, or dullness from various types of chemical treatments or polishes. To compound the ambiguity, grading services do not treat silver coins that have been carefully "dipped" in anti-tarnish solutions as "cleaned", although such "dipping" may reduce the numerical grade they award the coin. However, coins that have a "washed out" appearance due to being dipped too many times or for too long will likely be deemed to have been "cleaned". (Dipping is unacceptable for copper and apparently copper-nickel coins and will almost certainly result in a "details" grade as "cleaned" or "recolored".)
"Cleaned" coins vary in appearance from hideous to fairly attractive depending on the nature and severity of the "cleaning". In my opinion, the more attractive ones are collectible at an appropriate discount. Additionally, even experienced collectors and dealers may disagree over whether a particular coin should be described as "cleaned" and, if so, the severity of the "cleaning".
I have a "Custom Set" on the NGC Registry that includes only coins that NGC or PCGS "details" graded as "cleaned" and a few that were numerically graded but that I regard as "cleaned".Characteristics of "Cleaned" Coins - Custom Set (collectors-society.com)Hopefully, the photos and descriptions in this set will provide you with some guidance. However, you will need to examine a number of original and "cleaned" coins in person to really understand the differences.
For NGC's explanations, see the following:
NCS Conservation: Effects of Improper Cleaning | NGC (ngccoin.com)
