By Alan Chenkin, I like to keep things in good shape
The general rule of thumb is to never clean Coins. Ever. This is particularly important with valuable coins, because a speculator might clean the Coin to improve it’s worth - but most cleaning actually is visible to coin graders, and such attempts actually reduce the coins value. But there are times to clean a coin, and consider the best way to handle them - look at this from the internet:
How to Clean Coins & Handle Old, Rare Coins - Numismaster
How NOT To Clean Coins: Tips On Cleaning Coins | The U.S. Coin Guide
Learn How to Clean Coins Safely and Easily - The Spruce
How to Clean Coins - Wikihow
If you are considering selling the coins, definitely do not clean them; store them separately and bring them to a dealer for appraisal. If your coins have sentimental value, souvenirs of a trip, or a gift from a friend, preserve them in a holder or frame, and clean them if necessary - the sentiment is worth far more than the coin.
There is nothing wrong with wiping your coins with an athletic sock or polishing cloth, as these do minimal invasive damage to the coin. You may also want to polish a coin that is deteriorating due to corrosion or oxidation.
After you polish your coins, reduce any further damage by keeping them in plastic holders or traditional coin flips.
Amazon.com: Coin and Currency Collecting Starter Bundle with Black Album - includes a coin album, 20 pocket pages, 2x2 coin holders, currency holders and coin box - all the coin collection supplies you need to get started: Toys & Games
A fun thing to do with some coins is to use them as jewelry. In that case, having a clean finish will be necessary, and the finished piece may be worth more than the coin itself.
Look what you can do with a quarter! (Bezel from Amazon)
Here is how you can put an amazing shine on a coin:
If you are unsure as to clean your coins or not, bring them to a coin dealer and ask! Most are helpful professionals, and have a wealth of knowledge. You can also get an idea from these sites on coin grading, especially when dealing with a coin you suspect has value:
Coin Grading: How To Determine The Grade Of The Coins In Your Collection - The Fun Times Guide
Coin grading - Wikipedia
How To Grade Coins Using the Coin Grading Scale - Coin collecting guide for beginners
The Westin St. Francis Hotel washes it’s coins, and has an employee dedicated to the task! “Rob Holsen is the coin washer at the Westin St. Francis Hotel, and perhaps the only coin washer on Earth. He said the hotel on Union Square started washing its coins in 1934 when the general manager noticed a woman's white gloves getting dirty.” From https://www.nbcbayarea.com/news/local/Coin-Washer-Cleans-SF-Hotels-Money-128219193.html
Hotel ruins millions of coins for collectors
Remember to have fun with your collection! Clean or not, sort your pocket change, and see where your coins have traveled from in the world!
Thanks for reading my Blog!
Edited from my Answer on Quora.
