Satin glass Mother of Pearl (MOP)

Mother of Pearl (MOP) is so named because of its lustered or "pearlized" surface. It is generally made of three layers of glass: 1–a clear outer layer; 2–a middle colored layer; and 3–an inner casing, usually white. MOP was made by blowing or placing a gather of glass into a mold to give the gather a raised pattern. This was then dipped into or rolled over the clear glass. The clear layer runs across the top of the raised pattern, trapping air in the gaps below. These trapped pockets of air reflect and spread light back through the outer surface to give MOP its glowing pearl-like luster.

Different molds created different patterns of air-trapped designs. MOP is generally named for these designs, such as Diamond Quilted and Rain Drop. Some of the other pattern names include Herringbone, Zipper, Peacock Eye, Flower and Acorn, and Swirl. Victorian MOP is usually a pastel color such as blue, pink or apricot, but can be found in a wide range of other colors. Rainbow MOP refers to pieces with three or more separate colors that usually appear as bands or stripes.