Protecting and caring for fine jewelry

Fine jewelry is worth protecting and caring for properly if it is to give maximum pleasure over many years. The Jewelers of America Inc., an association of jewelry retailers, shares these hints for effective care:

* Even if you wear your diamond engagement ring, or any other diamond ring, for 24 hours a day, you should still remove it when doing rough work. Although a diamond is durable, it can be chipped by a hard blow, and chlorine bleach can discolor the mounting.

* Diamonds get smudged, soiled, and dusty from lotions, powders, soaps, and natural skin oils, and mountings can be discolored by the chemicals in the air. Clean them in one of four ways to maintain their brilliance.

The first way is to place the piece in a small bowl of warm suds made with any of the mild liquid detergents used in the home. Brush pieces with eyebrow brush or soft toothbrush. Transfer to wire tea strainer and rinse under running water. Dry with soft, lintless cloth.

A second method is to soak half an hour in a mix of half-and-half solution of cold water and household ammonia. Lift out and brush lightly with soft toothbrush, swish once more in solution, and drain on tissue paper. The quick-dip method, using any of the commercial liquid jewelry cleaners on the market, is a third way, but instructions should be read and followed explicitly.

The fourth method is ultrasonic cleaning with any of the many types of these small machines now on the market. Such a cleaner consists of a metal cup, filled with water and detergent, and high-frequency turbulence, which provides the cleaning action. Each machine is slightly different, and instructions should be read and carefully followed.

To care for karat gold jewelry, always separate gold jewelry in a partitioned jewel box to protect against scratching. Remove dingy film or tarnish with a prepared jewelry cleaner or by using soap and water with a few drops of household ammonia mixed in. Grease can be removed from karat gold jewelry by dipping into plain rubbing alcohol. A soft chamois cloth purchased at any hardware store is an inexpensive way to keep gold jewelry lustrous and shining.

Pearl jewelry should only be put on after applying make-up, hair spray, and perfume. It should be kept in a chamois bag or wrapped in tissue paper when not in use. Never clean pearls with chemicals or abrasives, but wash them with mild soap and water.

The Dallas-based Zale Corporation gives these tips for the protection of fine jewelry.

* Maintain an up-to-date inventory of all valuable jewelry, including photographs of each piece, to show styling and size. Photograph (a simple Polaroid will do the job) each piece next to a ruler in order to record its accurate size. Such photographs will help in identification in case of loss or theft, and in making insurance claims.

* Periodically update your appraisals and insurance coverage.

* Have diamonds ''gemprinted'' - a new method of laser photography that, in effect, takes a ''fingerprint'' of the internal facets of a diamond. This provides court-approved evidence of identification and ownership. Gemprinting is available through many established jewelers for a nominal fee.

* Keep all inventory records, photographs, purchase receipts, etc. separate from your jewelry, such as in a safe deposit box.

* Do not subject jewelry to excessive heat. Opals, for instance, should not be worn to the beach, where sand can scratch and heat can dehydrate the moisture of the stones, with resultant cracking and loss of brilliance.

Nancy Michel and Alexandra Watkins, the new partners of Atelier Janiye in Boston, both worked for a number of years with the founder of the atelier, the late Miye Matsukata. These young custom jewelers say that rings take the most wear and tear and therefore require the most regular checking for worn prongs and loose stones.

They caution that ammonia should never be used in cleaning opals, emeralds, pearls, amber, and most jade and lapis lazuli stones. They do use soapy water and ammonia to clean diamonds, rubies, and sapphires, and they leave jewelry to soak from an hour to overnight.

The partners offer several warnings. When soaking rings in a bowl or jar, mark or note in some way so that you will not forget and accidentally dump out the water and the jewels. Never wrap pieces of jewelry in pieces of Kleenex when not in use, for these can be mistaken as household trash and tossed out. While traveling, always carry precious jewelry with you, either in your purse or in hand luggage. Never leave jewelry lying around hotel rooms when you are not present. At home, as a matter of everyday security, keep jewelry out of sight and not visible to anyone who comes into your home.