A coin which has been cleaned in a soap solution, the most popular of which is called Jewel Luster, is said to have been dipped. The term "dipped" is not necessary in, say, a catalog description of a coin, unless the dipping has caused noticeable dulling of lustre, or an otherwise unnatural appearance (typically on copper coins). The practice of dipping coins is not advisable, except by bonafide experts, and then only on rare occasions.
