Iridescence is a phenomenon that the eye perceives as patterns of spectral colors. It is formed by interference of light waves reflected from the lower and upper side of one or more (semi) transparent layers, and depends on the position of the observer, the angle of observation or the angle of the incident ray of light.
White light is known to be composed of a full continuous array of colors of the visible spectrum. We can see this most clearly when the light passes through an optical prism. Each color leaves the prism following its own wavelength, causing the light to decompose into rainbow colors. The color of an object is determined by the absorption/reflection of wavelengths of a certain part of the spectrum characteristic of a specific surface. Each chromatic surface reflects one part of the electromagnetic spectrum, while the remaining radiation is absorbed. When white light passes through a thin transparent film (layer or coating), part of the light is reflected from the upper surface of the film and part from the surface below one or more layers. When the reflected rays merge (constructive interference) they create the effect of iridescence.
Iridescence is present in nature – it can be seen on some minerals, feathers of some birds, insects, fish, shellfish, and as part of many natural phenomena. Since it causes a sensation in the visual system, it is one of perceptual observations that aroused interest among applied artists. A special impetus for the creation of the effect of iridescence was given by ancient glass on which naturally, due to the long stay underground, thin flakes formed on the surface resulting in an overflow of colors. Artist and designer Louis Comfort Tiffany (1848 – 1933), son of the founder of the world’s leading jewelry company, is credited for patenting the production of irdescent glass – Favrile glass (from fabrile, possibly denoting handcrafted origin). Multiple sources note that the designer was influenced by the glass collection of the Victoria and Albert Museum (former South Kensington) during his visit.
In the production of glass and also ceramics, iridescence is formed by treating the surface with metal oxides and exposure to acid vapors in a reducing atmosphere. Today, some contemporary manufacturers of paint, and even cosmetics, fashion clothing and accessories, have iridescent paints and textiles as part of their their offer that might seem as an invention from a future age but also reflect some eclectic luster.
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