The softness of pearls and their low resistance to heat and chemicals mean that special precautions must be taken when cleaning them. Keep in mind the following guidelines:

• Do not use commercial jewelry cleaners on pearls unless the labels say they are safe for pearls. Many of them contain ammonia, which will cause deterioration.

• Never clean pearls in an ultrasonic cleaner. It can damage the pearls and wash out the color if the pearls have been dyed.

• Never steam-clean pearls. Heat can harm them.

• Never use detergents, bleaches, powdered cleansers, baking soda or ammonia-based cleaners on pearls.

• Do not use toothbrushes, scouring pads or abrasive materials to clean pearls. They can scratch their surface. If there's a lump of dirt that can't be rubbed off with a soft cloth, try using your fingernails. They have a hardness of only 2 1/2 or less.

Cleaning pearls is not complicated. After you wear them, just wipe them off with a soft cloth or chamois which can be dry or damp. This will prevent the dirt from accumulating and keep perspiration, which is slightly acidic, from eating away at the pearl nacre.

If the pearls have not been kept clean and are very dirty, they can be cleaned by your jeweler or they can be washed in water and a mild soap such as Ivory or Lux liquid (some liquid soaps, such as Dawn, can damage pearls) and cleaned with a soft cloth. Pay attention to the areas around the drill holes where dirt may tend to collect. After washing them, lay the pearls flat in a moist kitchen towel to dry. After the towel is dry, they should
be dry. Do not wear pearls when their string is wet. Wet strings stretch and attract dirt which is hard to remove. Likewise do not hang pearls to dry.