Carnival Glass was initially called Iridescent Ware when it was introduced in late 1907. The name carnival glass was not commonly used until collectors in the 1950s began to refer to it as such. This innovative glassware typically featured a vivid metallic sheen of changing hues on pressed glass articles made in highly-patterned moulds. The secret behind the Iridescent Ware was a special spray of metallic salts on the glass while it was very hot.

Made as both functional and ornamental objects and found in a wide array of colors, carnival glass is an inexpensive pressed glass, often called dope glass by glass factory workers because of the process of applying the iridescent coloring, which is known as doping. Its production can be traced back to as early as 1907, with many, many different pieces in over 150 distinct patterns. It did not, however, command the expected prices, and was subsequently discounted heavily.

This glass is available in many translucent colors like primarily amethyst, marigold, coblat, green and red. It is also made in opaque white which is also referred to as milk glass. This glass was also availale in semi-transparent or translucent pale green and was named as Vaseline or uranium glass before the harmful effects of radiation were known. Vaseline glass and uranium glass have small amount of uranium salts which make faint green glass glow on reaction with UV light.

Millersburg glass Company, Ohio was one of the largest producers of this kind of glass. Though the first glass product of the company were crystal, the Millersburg plant decided to produce iridescent glassware looking to the popularity of it. In this way the Millersburg Company brought out its line of Radium glassware.

The prices of Carnival glass vary widely depending on their quality and availability. This glass is a highly collectible item with some of the pieces worth very little, while other, rarer items command thousands of dollars. There is a very active market for this item since it has become an antique glass collectible.

The carnival glass is very difficult to identify. Unfortunately, most of the manufacturers avoid including a maker's mark in their product. Others did so only for part of the time they manufactured the glass. The process of identification involves matching of patterns, colors, sheen, edges, thickness, factors found in old manufacturer's trade catalogs and other known examples, or other reference material. Identifying this glass has become a challenge even to experts since many manufacturers produced duplicates of their rivals' popular patterns.

At the time of introduction in late 1907 the carnival glass was called as Iridescent Ware. However, people started using the name carnival only after collectors in the 1950s began to refer to it as such. Among the greatest producers of this type of glass was Millersburg glass Company in Ohio. The first glass products by that company were crystal however the Millersburg plant decided to follow success for iridescent glassware. There is a very active market for this item since it has become an antique glass collectible. So even for an experienced expert this is a hard task.