I am cleaning my very first ancient coin. I purposely chose one that does not seem to have any real design features on it at all, so that if I mess it up, it won't matter. I soaked it for about 20 minutes in a bit of water with dishsoap, and scrubbed it with an unused toothbrush also. The coin is dry, and looks much darker than it did in its raw, uncleaned state. What I need to do now is to understand the surfaces of this coin. There are darker brown parts, which seem to be a series of layers on the coin, and lighter greyish light brownish parts at about 11 o'clock, 1 o'clock, and in the center, which are buried underneath those layers. I am wondering: are the dark layers I'm looking at the patina, or are they just crud to be removed? Next time, I'll probably try using olive oil rather than dish soap. If anyone has any favourite tips regarding methods that work for them, I'm all ears. I've got 12 left to play with! If the coin in question is too far gone for anyone to answer, please let me know. My thanks to anyone who can help me out!