Maintaining a clean diamond can sometimes be difficult, as jewelry settings can obstruct cleaning efforts, and oils, grease, and other hydrophobic materials adhere well to a diamond’s surface. Some jewelers provide their customers with sudsy ammonia cleaning kits. Many jewelers use steam cleaners. Some other jewelers sell small ultrasonic cleaners. Home-based cleaning methods include immersing the diamond in ammonia-based or ethyl alcohol-based solutions, or even a solution of mild grease dissolving detergent and warm water. Silver jewelry can be cleaned using aluminium foil, baking soda, and hot water. However, this practice is not recommended by most jewelers. Certain types of cleaning can damage some jewelry. For example, some class rings are coated with a dark pigment, called antiquing, to darken their appearance. Some gemstones, such as white topaz, have an overlay to produce certain colors. Ultrasonic cleaning can remove this coating, if it is not a quality piece. Ultrasonic cleaning is also contraindicated for opals, pearls and amber, and any other gemstone that is porous. Gemstones that are glued in (a common practice with semiprecious stones in non-precious methods and in class rings) should not be placed into an ultrasonic cleaner. An ultrasonic cleaner can cause stones that are loose in their settings to come out. Jewelry should always be examined for overlays and loose stones prior to cleaning with an ultrasonic cleaner or a steam cleaner.
Although it is not one of the 4 Cs, cleanliness affects a gemstone’s beauty as much as any of the 4 C’s (cut, carat, color, clarity).
A clean gemstone is more brilliant and fiery than the same diamond when it is “dirty”. Dirt or grease on the top of a diamond reduces its luster. Water, dirt, or grease on the bottom of a gemstone interferes with the gemstone’s brilliance and fire. Even a thin film absorbs some light that could have been reflected to the person looking at the diamond.
Colored dye or smudges can affect the perceived color of a gem. Historically, some jewelers’ diamonds were mis-graded due to smudges on the girdle, or dye on the culet. Current practice is to thoroughly clean a gem before grading its color as well as clarity. How a gem can be safely cleaned depends upon its individual characteristics and therefore its susceptibility to damage.