Ketchup, vinegar and salt, lemon and salt and apple cider vinegar can all be used as soaking solutions to help clean dirty coins. Light scrubbing of the dirty coins may be used to help speed the cleaning process. Collector coins should never be cleaned without consulting a professional.
If a coin is a collectible, cleaning it can dramatically reduce its value. If average coins are dirty and need cleaning, though, they should be left to soak for several minutes in a bowl of ketchup, vinegar and salt, lemon and salt or apple cider vinegar. When scrubbing coins, do so gently and only for as long as required to remove dirt, otherwise damage to the coins may result.