answer 1
Real pearls are created in layers, called nacre, and they are very prone to scratching, and can be damadged by rubbing against one another. The knotting is dual-fold, to protect the necklace not only for damage, but also to save pearls, if the necklace becomes caught, or breaks. Some folks use two knots, so if it breaks, no pearls are lost, and a knot before attatching the clasp. Also, never use any cleaner on pearls, only a damp cloth, then dry, and air dry over night, before putting away in it's case.