Mirrors

MIRRORS

A mirror is a surface that forms an image when light rays fall on an object placed in front of it. The mirror can be flat or curved, and is usually produced of glass with a reflective coating added to it.

GLOBAL ORIGINS

 

The earliest man-made mirrors were from polished stone and mirrors made form black volcanic glass, Obsidian. They were only about three inches in diameter. Such mirrors have been found in Anatolia (modern-day Turkey) dating back at least 6000 years.

The Ancient Mesopotamians produced polished metal mirrors from around 4000 BC. They crafted them out of flattened, polished copper.

The Ancient Egyptians started using these from around 3000 BC. The mirror they produced had rounded shapes, sometimes with ornamentation on the back, and usually with a handle for self-viewing.

Mirrors made from polished stone came to be known in Central and South America from about 2000 BC.

Chinese manufactured bronze mirrors from around 2000 BC. The mirrors began to be made from metal alloys, a mixture of tin and copper called “speculum” that could be highly polished to make a reflective surface. The production spanned to the Indian subcontinent. Such mirrors were very valuable items in ancient times and were only affordable to the wealthy!

Metal-coated glass mirrors are said to have been produced for the first time in Sidon (modern-day Lebanon) in the 1st century AD.

The technique for creating crude mirrors by coating blown glass with molten lead was discovered by the Romans. In Greco-Roman culture and throughout European Middle Ages, mirrors were simply slightly convex disks of metal (bronze, tin or silver) that reflected light off their highly polished surfaces. Pieces of glass covered with lead were also found in Roman graves dating from the 2nd-3rd century.

Some time during the early Renaissance, a superior method of coating glass with a tin-mercury amalgam was perfected in Europe. In the 16th century, Venice (very famous for its glass-making expertise) became a center of mirror manufacturing. The Saint-Gobain factory, established by royal initiative in France, was an important mirror producer too. By the middle of the 17th century, mirror was extensively made in London and Paris.

 

PRODUCTION

 

Glass, chrome and aluminum are the materials commonly used to create typical mirrors. Mirrors that must withstand extreme temperatures are made from glass composed of boron and silica.

From the late 17th century onward, mirrors-and their frames-played an increasingly important part in home decoration. The early frames were usually made of ivory, silver, ebony, or tortoiseshell. Later on, the frames were decorated with floral patterns or classical ornaments.

In 1835, German chemist Justus von Liebig developed a process for applying a thin layer of metallic silver to one side of a pane of clear glass. This technique was soon adapted and improved upon, allowing for the mass production of mirrors. Some years later, silver became the most common metal coating, leading manufacturers to coin the term “silvering.”

Before 1940, mercury took the lead, as it did not tarnish and was easy to spread evenly over the surface of glass. Eventually, manufacturers abandoned this practice due to the toxicity of this liquid.

Today most mirrors are coated with chrome or aluminum. The mirror substrate is first shaped, then polished and cleaned, and finally covered.

Shatter-resistant mirrors are made from an optically perfect acrylic sheet, which is protected on the back with a durable scratch-resistant coating and with clear polyethylene film on the front.

Mirrors used for scientific purposes are often coated with other material, such as silicon nitrides and silicon oxides. These serve as protective finishes, as they are scratch resistant. They are also better reflectors than their metallic counterparts. Scientific mirrors are sometimes coated with gold and silver to reflect light of different wavelengths and produce a desired effect.

 

USES

 

As aids to personal grooming. They may be handheld, mobile, fixed oradjustable. The “cheval glass”, for instance, can be tilted.

Convex mirrors provide a wider field of view than flat ones and are used on vehicles, especially large trucks, to minimize blind spots. They are also placed at dangerous road junctions and corners of parking lots to ease reversing and prevent vehicles from crashing into shopping carts.

Convex mirrors are sometimes used as part of security systems, so that a single video camera can show more than one angle at a time.

Mouth mirrors / Dental mirrors are used by dentists to allow indirect vision and lighting within the mouth. Their reflective surfaces may be either flat or curved.

To attract the attention of rescue helicopters. Specialized type of mirrors are available and are often included in military survival kits.

Microscopic mirrors are a core element of many of the HD televisions and video projectors. The DLP chip used is, in fact, an array of millions of microscopic mirrors.

Mirrors are integral parts of a solar power plant. They use concentrated solar power from an array of parabolic troughs.

Telescopes and other precision instruments use front silvered mirrors, where the reflecting surface is placed on the front surface of the glass. Silver or aluminium are used to reflect light.

Dielectric mirrors are used in lasers. By varying its depth, the range of wavelengths and amount of light reflected from the mirror can be specified. The best mirrors of this type can reflect > 99.999% of the light!

Mirrors for radio waves (reflectors) are important elements of radio telescopes.

To produce enhanced lighting effects in greenhouses or conservatories.

As a design theme in architecture, particularly with late modern high-rise buildings in cities. However, there are several risks which are doubted to be associated with such architecture. For instance, the ignition of objects around these buildings during hot summers.

Painters use mirrors to draw someone gazing into a mirror as a kind of abstraction. Similarly, in movies and still photography an actor is often shown ostensibly looking at himself in the mirror, and yet the reflection faces the camera.

Mirrors are used also in some schools of feng shui, to achieve harmony with the environment.

A decorative reflecting sphere of thin metal-coated glass, working as a reducing wide-angle mirror, is sold as a Christmas ornament called a “bauble”.

Illuminated rotating disco balls are covered with small mirrors are used to cast moving spots of light around the dance floor.

The hall of mirrors, commonly found in amusement parks, is an attraction in which a number of distorting mirrors are used to produce unusual reflections of the visitor.

Mirrors are often used in magic to create an illusion. One effect is called the “Pepper’s Ghost”.

For houses with small rooms, mirrors can be a perfect choice, because they can stimulate depth. Putting big mirrors in rooms with limited spaces can provide bright and spacious feel. Mirrors are also used in narrow hallways to make them appear wider and longer.

Mirrors in windowless hallways and bathrooms reflect the light and make them look bright, so that there’s no need to use bulbs everywhere.

Stylish decorative mirrors are used to cover wall blemishes.

 

INTERESTING FACTS

 

People first started looking at their reflections in pools of water.  When an anthropologist introduced mirrors to the isolated Biami people of Papua New Guinea in the 1970s, the tribe reportedly met their eerie reflections with terror, rather than fascination.

Concepts of the soul are associated with mirrors, which results in a wealth of superstition surrounding them. According to an old Roman legend, breaking a mirror causes 7 years of bad luck because the soul which shatters with the broken mirror regenerates every 7 years. In many cultures, mirrors are covered when someone dies because a mirror can trap the soul of the deceased.

The Mesoamerican Cultures that lived developed specific traditions and religious ceremonies regarding mirrors. Prevalent ones were practiced by the Maya, Aztecs and Tarascans. For instance, there was a strong belief that “the thought that mirrors served as portals to realm that could be seen but not interacted with”. Association of mirrors with water came from the ancient beliefs that reflective water can show us the future; Fire was celebrated because of the mirror’s ability to channel sunlight and create fire; Mirrors were decorated with jade beads and used in burial ceremonies and offerings; Some mirrors depicted gods with mirrors in their eyes.

Only a few animal species have been shown to possess the ability to recognize themselves in a mirror. These are species of some monkeys, bottlenose dolphins, orcas, elephants and European magpies.

 

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