I am not recommended you to clean your coins, but if you really feel you have to, please make sure you only try to clean cheap coins that you have. Cleaning a coins to make them shiny and look like new do not improve the grade of your coins. Most of the time, it will only damaged your coins and lower their grade/value. I am sharing this post in 2009 to let my readers know how people clean coins and maybe helping them to detect clean coins.
These coin cleaning methods taught by uncle Thiru from Thiru's numismatic & handicraft in jalan persiaran raja muda musa, Port Klang (He already closed his shop few years back).
I meet him in his shop in 2009. When I meet him that day, he is cutting some lime and squeeze their juices into a bowl. When I asked what exactly he is doing? He told me that he is cleaning his coin collection. He has been doing this for many years since he start collecting. I am asking him about his tips on doing coin cleaning with lime juices and here are some of what he told me that day for your knowledge. If you never cleaned your coin before, I advise you not to try them with your valuable coin.
This method of cleaning is just for coin with normal dirt, light haze, green spots or oily film. What you need is some lime (limau kasturi, limau purut or limau nipis) that you can buy from Malaysia wet market for below 10 ringgit per kilo. If you cannot find lime, you can also try lemon juices. Squeeze that lime juices into a bowl that you want to put your coin. You need to put your coin at for least two days. Just make sure you separate them according to their metallic content. I can see that Uncle Thiru separated the silver coin from the bronze coin in a different bowl. He told me never mix coins of different metal together or you will be having a problem later with the other coin metal stuck to other coins.
After two days, pick up that coin and clean them with soft cloth towel. Make sure you clean your hands with soap before you touch your coin. This is to make sure all the dirt that on your hands is not transferred to your coin. Never try to rub and scrub your coin. Just clean your coin gently using that soft cloth towel. After you clean them, soak them in a coconut oil base soap water for one day. Uncle Thiru's told me he get his coconut oil soap from Amway. After soaking your coin with soap water, rinse them with running tap water for 3 to 5 minutes. Then pat it dry with clean soft cloth towel, try not to do it with any rubbing motion that can scratch your coin.
For hard to clean dirt on your coin, you need to used other method. Some of the method suggested by Uncle Thiru is to soak that coin for 10 days in lime juices and then boil them with soap for one hour. Will try to take picture of this method next time. I am suggesting you that there is no need to clean your coin because it will make it devalue if you don't know how to do it. I am also not sure if Uncle Thiru method using lime is a good method for cleaning your coin.
If you want to try this method to clean your coins, just remember that lime/lemon juices are acidic. It can clean the dirt on your coin surface but also can damaged your silver coins if you don't rinse your coins with water properly.