Carnival glass is a pressed glass that was sprayed with metal oxides and then reheated. The oxides make the glass iridescent which gave it the appearance of being multicolored when viewed in sunlight or other bright light.
While still made today, carnival glass enjoyed its biggest heyday in the early 1900's. Major US manufacturers were Fenton, Northwood, Imperial, Millersburg, Dugan and US Glass. Carnival glass was also made in Great Britain, Europe, Australia, Mexico and South America.