Favrile iridescent glass is a type of art glass patented in 1880 by Louis Comfort Tiffany. The iridescent effect of the glass was obtained by mixing different colors of glass together while hot. The trade name Favrile was derived from an Old English word, fabrile, meaning handcrafted. Art glass normally means the modern art glass movement in which individual artists working alone or with a few assistants to create works from molten glass in relatively small furnaces of a few hundred pounds of glass. ... A patent is a set of exclusive rights granted by a state to a person for a fixed period of time in exchange for the regulated, public disclosure of certain details of a device, method, process or composition of matter (substance) (known as an invention) which is new, inventive, and... 1880 (MDCCCLXXX) was a leap year starting on Thursday (see link for calendar). ... Louis Comfort Tiffany (1848-1933) circa 1908 Louis Comfort Tiffanys The tree of life stained glass Louis Comfort Tiffany (February 18, 1848 - January 17, 1933) was an American artist and designer who is best known for his work in stained glass and is the American artist most associated with... The iridescence of the Blue Morpho butterfly wings. ... A trade name, also known as a trading name or a business name, is the legal name of a business, or the name which a business trades under for commercial purposes. ... Old English (also called Anglo-Saxon) is an early form of the English language that was spoken in parts of what is now England and southern Scotland between the mid-fifth century and the mid-twelfth century. ...

Favrile glass is distinguished by brilliant or deeply toned colors, usually iridescent like the wings of certain American butterflies, the necks of pigeons and peacocks, the wing covers of various beetles. (Louis Comfort Tiffany)

A typical Tiffany's favrile glass window

In 1865 L.C.Tiffany traveled to Europe and in London he visited the Victoria and Albert Museum, whose extensive collection of Roman and Syrian glass made a deep impression on him. He admired the coloration of medieval glass and was convinced that the quality of contemporary glass could be improved upon. In his own words, the "Rich tones are due in part to the use of pot metal full of impurities, and in part to the uneven thickness of the glass, but still more because the glass maker of that day abstained from the use of paint".

He wanted the glass itself to transmit texture and rich colors and he developed a type of glass he called Favrile. Favrile was simply a combination of common white glass, call opalescent, used by the early cosmetics industry to bottle its creams and ointments, and clear colored glass, called antique, used in stained glass windows for centuries.

Artists, who tried to combine these two glasses before Tiffany, only produced a dull fragmented material that inhibited the flow of light. But Tiffany arrived at Favrile through extensive studies in chemistry and experimentation.

Tiffany developed a whole range of unique glassware by trying out and perfecting new techniques in the furnace. The glass itself was of the best quality, its colors achieved by the addition of metallic oxides, variable by temperature within the furnace.

His lustering technique, with its iridescent effect, was the most important because it was his hallmark, used in many different wares. This involved dissolving salts of metallic oxides in the molten glass, so creating the chosen colors - soft greens, blues, golds, etc. The metallic content was then brought to the surface by subjecting the glass to a reducing flame and spraying with another chloride. This treatment caused the surface to crackle into a profusion of tiny lines that refracted light. The skill of the blower was paramount in this, because Tiffany glass was free blown. Speed was necessary to achieve the desired effect before the molten glass cooled. With intricate Tiffany specialties, like the peacock feather motif or a jack-in-the-pulpit vase, executing this technique was very difficult.

Color in glass is a function of chemistry. By adding various metal oxides, glassmakers can create different colored glasses. In a series of difficult experiments, Louis Comfort Tiffany added metal oxides to batches of clear molten glass to produce the exact tones he desired so that he could create a vast spectrum of colors and " paint" with glass. Here are the results of his and other chemists' experiments:

Cupric oxide = blue
Iron oxide = green
Manganese oxide = purple
Gold, copper or selenium = red
Coke, coal or carbon oxides = amber
Manganese + cobalt + iron = black

Iridescent glasses, such as Tiffany’s Favrile and Carder’s Aurene, are produced through a complex chemical process. First, rare metal compounds are added to molten glass while the glass is subjected to a flame. Each metal produces a different color effect, such as blue or gold. Then, the glass is sprayed with chloride (Cl2), which causes fine lines to erupt all over the surface. These lines pick up the light and produce a shimmering appearance.