All cultured freshwater pearls are delicate gems that are made of a natural product called calcium carbonate. This product is drawn from the lake or river by the mussel that the pearl lives inside.
The products that harm pearls the most are the perfumes, hair sprays, cosmetics and make-up that we do not give a second thought to wearing. Along with other household chemicals, if sprayed near pearls these products can build up on the pearl and damage the luster.
The nacre can become marked, dull, pitted and generally lose that marvelous luminous luster that defines a pearl.
Do not clean pearls using any of the jewellery cleaners made for gold or silver jewellery. Also do not use the ultrasonic cleaning sets as the vibrations can cause the pearls rub against each other.
If the pearls are old, and the luster is dulling, wipe them with a soft damp cloth that has been dipped in a very gentle natural soap solution, and then wipe them with a detergent free damp cloth and allow them to dry FLAT on kitchen paper. Once the pearls have dried, a cloth with a fine smear of olive oil wiped over them will help restore some luster.
Good pearls will last longer if they are restrung every six months to every two years, depending upon the frequency they are worn. They should only be restrung with silk thread or special nylon necklace cord. Other yarns like cotton break and deteriorate more easily. The silk is best knotted between each pearl. The knot not only helps keep control of your pearls should the silk break, but also helps stop the pearls rubbing against each other.
The newer modern alternatives to knotted strung pearls, are designs that incorporate pearls spaced on wires and held in place by gimps and glued. These designs appear to float on the neck, but must always be stored as flat as possible to prevent the wire from becoming tangled or miss-shaped.