Just What Constitutes "Cleaning" Of A Coin?

When you see the designation "cleaned" or "improperly cleaned" it means there is evidence that the coin has been rubbed, polished, etc. You might not be able to see these marks without magnification.

Oh I forgot one question. Has anyone used acetone or verdicare on a medieval coin? Results?

Cleaning, by definition in the coin hobby, is what happens when metal from the coin itself is removed/marred.

Rubbing, polishing, scraping, etc. do this.

Conserving coins is acceptable and means the removal of foreign material without removing/scarring the coin's metal.

In other words, if you can tell dirt has been removed, you probably lessened the value of the coin.

Any solvent which will not alter the metal itself is OK to use.

Here is a thread containing a great guide by our member BadThad:
http://goccf.com/t/57008#447106

Also, using something that will not scrape the coin surface to remove dirt is fine. Some people use a toothpick. I have found porcupine needles work well for the gunk in the corners of the letters and mint marks. Pocupine quills are inexpensive and available on ebay. I put the coin under a microscope and use the quill to scoop away the gunk. The quill does not scratch the metal and so you cannot tell anything was done. However, this action (and with a toothpick) very, very rarely can make a tiny scratch if the utensil you used happens to push down on a hard piece of micro-gunk and you make a micro scratch by moving it.

If you wanted to practice on silver, you could likely get common date "junk silver" from a coin shop. You can get common date uncirculated coins this way.

Chemicals such as E*Z*EST and MS70 are inexpensive chemicals used to brighten coins and, if done in the correct manner, are said to be undetectable. However, it must be remembered "shiny"does not mean valuable, and it also is very easy to ruin a coin using these two chemicals.

E*Z*EST is a "dip" for coins that will quickly remove a natural look of the luster if the coin is left in for more than a couple seconds (literally). But if a person is practiced (use junk please!), they can get results which TPGs will accept and grade.

MS70 is probably best used by wetting a cotton swab and rolling the swab onto the coin surface or dabbing at a spot on the coin with discoloration. Again though, caution! Too much exposure to the chemical is discernible. Practice makes perfect.

Even though I have conserved quite a few coins with both of the above, I go by the idea that more than one very quick application/bath is a lot better at limiting the risk of ruining the coin. Some people also dilute the chemicals with distilled water to limit the impact the chemicals can have at one application/dip. Either way the distilled water bath should be immediately handy.

It is important to make the distinction between "dirt" - foreign matter sitting on the surface of a coin - and the metal of the coin itself. Removing the metal itself is what is usually considered "bad cleaning" - though in some cases, such as ancient coins or other coins dug up from the ground, "bad cleaning" may be the only option available.

It's all to do with chemistry. If it's "dirt", then removing it is perfectly OK, provided the removal is done in such a way as to not damage the coin, because the dirt hasn't reacted chemically with the metal. Corrosion products were once part of the metal itself so you generally don't want to remove them unless leaving them on the coin is going to cause further damage to the coin.

"Dirt" isn't just literal dirt, it's anything of non-metallic origin that might stick to the surface of a coin: paint, glue, varnish, sticky-tape residue, and plasticizer residue that leaches out form certain plastics over time. These are all perfectly acceptable to remove from a coin. Many of those things listed above will be difficult to remove without some kind of solvent. Such a solvent should be chemically inert with regard to metals; "organic" solvents such as acetone, ethanol, methanol, hexane etc. are all acceptable. Acids (eg. sulfuric acid) and alkalis (eg ammonia) are not acceptable, as they actually react either with the metal itself or with the corrosion products.

"Corrosion products" covers a lot of phenomena and is given different labels depending on who is doing the labelling: oxidation, toning, patina, tarnish, rust, corrosion - these are all chemical damage caused by the coin being exposed to the environment. This planet does not like bright shiny metal, and from the moment a coin is made, the planet is doing its best to try to turn that piece of metal back into the mineral ores from whence it came, which is why coin collectors usually try to shield their coins from this environment. It should be noted that all corrosion products are considered "damage", and ought to be avoided on a coin. The main reason why cleaning is considered "bad" is that, when this layer of damage is removed, the underlying surface of the coin remains damaged - it's just that the damage is made more visible and obvious. The corrosion layer - particularly metal oxides - also often forms a protective barrier, preventing further corrosion (though this does depend on the chemical properties of the metal in question). So removing the corrosion products It also exposes fresh metal to the corrosive environment that cause the damage in the first place.

Some corrosion products are harmful to the continued preservation of the coin. "Green goo" that forms when plasticizer residue reacts with a coin is acidic, and will continue to damage a coin if not removed. "Bronze disease" is a contagious corrosion that forms on copper and bronze coins under certain circumstances, and can not only spread across the surface of a coin but can jump from coin to coin if the particles of dust beak off and land on another coin. These things have to be removed from a coin, to stop it from continuing to degrade. The resultant coin will still be damaged, and labelled as "cleaned", but at least some part of the coin will be saved.

This is why soaking a coin in acetone to remove old stickytape or green goo is perfectly OK, while "coin dip" such as E-Z-est (which is made from sulfuric acid and thiourea) is frowned upon.

Cleaning - A process that results in a non-market acceptable coin.

Conservation - Everything else

It's that simple!