1. Protecting pearls properly can make them last for centuries. One of the reasons

a pearl loses its luster or cracks is due to the mineral constituent of the pearl

being dissolved by weak acids. There are  several kinds of acids that pearls may

come in contact with. The acidic nature of perspiration is one such acid. Much

of the cotton that pearls are wrapped in when not in use us treated with an acid.

Another kind of acid that damages pearls is found in many modern cosmetics.

Cosmetic seep into the string canal and may penétrate into the layers of the

pearl and cause deterioration. The best protection to give a pearl to ensure

its long life is having it cleaned and restrung at prescribed intervals.

Where in the passage does it state that sweating can cause damage to a Pearl?