Carnival glass was introduced by US manufacturers very early in the 1900’s.  Northwood, Millersburg, Fenton, Dugan and other American companies produced a vivid spectrum of colors. The "carnival" finish refers to the iridescence, an outcome of a base glass color sprayed with a metallic salt solution which results in a lustrous surface iridescence. There were two standard finish effects to the sprayed pieces: most commonly produced was a satin finish. Satin has a finish much like oil on water.   A radium finish was introduced by the Millersburg Company and produced in limited quantities by other companies. The radium finish is a shiny, mirror like finish.   Pieces with a milky edge are known as opalescent.  With a somewhat endless, unique spectrum of colors and surface finishes, carnival glass enthusiasts enjoy a rewarding and endless search for new treasures, unearthing delightful finds in a myriad of venues.