While this document is long, it's well worth downloading and reading in its entirety, even (especially) for those of us who never intend to clean an ancient coin. In particular, I found two highly interesting and relevant items that I though would be worthwhile to share with the collectors on this site: 1. About desert patinas: "Regarding the so-called "desert patina," I have to say that it's not always great for the coin. I must clarify that I’m not trying to discourage anyone to stop liking “desert patina.” I just distrust it due to what I have seen. First, it's dirt, not really a patina. It's pretty dirt in some cases, for sure, but dirt it is. It's not necessarily that the coin neatly acquired sand in the fields, leaving the high points untouched. Granted, that might be the case for some coins. But what happened most likely is that someone stopped cleaning it once the high points were visible and you could identify the coin. "Second, there are people who actually glue sand to coins to recreate the "desert patina" in order to sell them as such, which is pretty bad for the coin and quite unethical. "Third, I have seen a lot of bad things happening under the dirt when I clean these coins. It is possible that you won’t see any changes in these coins for decades or even in your lifetime, but it has happened to me that in a few years or less I’ve seen decay on a few coins of this type. ... the dirt is collecting and maintaining humidity, and the dirt might have minerals that will react with the humidity and the air, and therefore with the bronze, ergo decay is a real possibility. Whenever I clean a coin with “desert patina” I often see either signs of bronze disease in different levels of progression, or actual corrosion on the metal under the dirt. These are minimal in some cases, but they point towards impending future decay. So yes, I do clean coins with "desert patina." This last observation partially explains why I've personally never been a particular fan of desert patinas. 2. Smoothing vs. cleaning: "Smoothing. I never smooth a coin. Smoothing involves flattening a defect on the metal of a coin, usually a scratch, by grinding the metal with a tool until it's even. This is done to the fields for the most part, but sometimes it's done to other features such as the bust and the devices. "When you even the surface by removing encrustations that had attached to the original surface it is not smoothing, it's cleaning. [Emphasis mine] When you alter a part of the original metal of the coin by grinding it down, it is smoothing." I have always considered the above italicized sentence to be the best definition of cleaning vs. smoothing, but I also believe that it's not always possible to distinguish between encrustations that had attached to the original surface vs. the original metal (i.e., irregularities) in the coin's surface.
in auctions they would (should) say smoothing when removing encrustations is meant. so not cutting into metal
