Before Cleaning your Old Coins. LOOK

You have heard time and time again 'Dont clean your old coins' And this is true up to 99% of the time. To the lay person a hard to read coin can simply be scoured with a tooth brush and geet or Arm and Hammer. Also the lay person is more prone to buff up an old coin and wear as a jewelry piece. The foremost action to do is to 'CHECK IT OUT WITH A COIN PROFESSIONAL' in other words have a numismatist look over them with you, or at the very least check out similar item here on okay.
Say your grandparents given you a hand full of old silver dollars, many of which were at one time Scotch taped to some old album. All the coins look the same except for the dates. They all look to be in mint condition (Mint State) two of the coins were your Great-Grand Father's birth year of 1884, you decide to take one of the '84 dated coins and polish away at the tape and buff up the coin to place into an album along with his picture. Later on down the line you learned about how some coins have mint marks. The other coins that were handed to you were never cleaned and still have that old tape residue. You noticed that the other 1884 coin was a Carson City mint and you are excited to know that the coin is worth over $100. (Old Grandpa, musta known that these coins were special) Now you happen to check for the mint mark (an 'S') on the polished one in the frame and find it to be worth $15,000! Now immediately you run down to the local coin shop and his offer to you is only $200. He says the value has been erased due to polishing.
I do hear stories like this quite often. And really it would take a degreed chemist to effectively clean a coin. It also takes a numismatist to evaluate rather or not a coin should be clean. It a fact that an attractive coin can increase value and or desirability. A same coin / same condition both in PCGS slabs the one with more 'eye' appeali.e. less or even toning tend to bring more at auctions. Though other aspects influence final price too. Even the US MINT washes all new coins before being released into circulation (hence the high number of coin marks even from mint rolled coins)
Now you have checked out your coins online and with a professional and you want to 'Clean your Coins' before auctioning them off or sending them to independent grading. You first want to know what it is that you're trying to get off your coin. As in above example; there is old tape residue and that can be removed with the use of ACETONE or nail polish remover. This should be left in for up to 24 hours. Copper coins with tape stuck on can be placed in acetone but usually leave an area of fresh pink surface. ACETONE is the best for removing stuck on debris like INK, TAR, and GLUE. AMMONIA is for lightning up silver and nickel coins that are going to be part of some set. Ammonia should be used on coins with light toning from a condition of near mint state to proof. Ammoniais oftenly used to remove that green patches that usually form on silver that has been stored in those PVC pouches for an extended time. Smoke usually coins thathave satout in the open like as in open folders or like the 50 State Quarter boards can be cleaned with liquid hand soap and warm water. Nickel and Copper coins can be de-smoked with plain rubbing alcohol. My advice is never to use anything stronger than grocery store bought ammonia to clean coins. Tarn-X, CLR, LimeAway, OxyClean are generally too harsh for aesthetic cleaning.Electrolysis cleaning method is usually ideal for cleaning coins that are found in dirt, normally by metal-detector scavengers. (if some one wants more information on electrolysis cleaning, I'll post later). One should NEVER use chlorine bleach, porcealin cleaners, or acids on your coins as these cleaners will likely eat-away at the metal thus darkening the surface. If you immerse your coins in a liquid solution, be sureNot to use a metal container or metal surface.
DRYING your coins should be done with great care. One good technique is to fold couple times some bath tissue and place in the middle of an old book, and by holding the edges place the coin on the tissue and fold over between the pages of the book. (see my guide on storage)
HARSH POLISHING your coins is an undertaking on your part. The US MINT does it for their sell of collectible items. Say you have a old silver half dollar that you know is worth but only $5 and wish to polish it to begee the center piece of your new bolo. My favorite polishing method involves a drill piece of duct tape, some metal polish and old piece of towel. Tape one side of the coin to a small polishing disc on your drill, face down on an area of the cloth dampened with polish, and run away for a few seconds. This removes that tarnish and mint luster, giving it a faux luster appearance. For a more lustrious less shiny appearance use toothpaste or baking soda.(gee back soon asimages will follow)