Synthetic and Manufactured Glass
Synthetic glass was first created by heating sodium oxide, or sodium carbonate, silicon dioxide (sand) and calcium oxide. If the calcium oxide was omitted you would get soda glass. Pure soda glass is highly soluble in water so it is not usable. It is believed that manufactured glass was originally used as a pottery glaze. Stone beads from the Bandarian Age of Egypt were glazed with manufactured glass and are the earliest known example of this type of glaze.
Egyptians are known to have made glass vessels by applying glass over a metal or wooden rod a little at a time. There is a light blue glass cylinder that was created by this method that is from the Akkad dynasty in 2600 BC. In 1200 BC glass began to be pressed into open molds. There is also some evidence that glass was first manufactured in Mesopotamia.
In 20 BC glass blowing was discovered along the Phoenician coast. The technique altered glass use from the creation of items such as ornaments and jewelry into more necessary items such as glass containers. In the Pompeii ruins high-quality items made of glass such as containers and window panes were discovered.
Today, the glass blowing of items such as art objects and vases is still basically performed in the same manner as it was originally done. After Rome’s decline, Constantinople became the center for glass work. Byzantine glass workers were very skilled in manufacturing mosaics and colored glasses. The center of glass working changed to Venice after the Dark Ages. By the end of the seventeenth century there were over 300 glass factories in Venice.
The Venetians created a hard soda glass that was highly transparent, ductile and colorless. Venetian glass looked like rock crystal so it was called cristallo. After this time glass factories grew tremendously in Europe. In England in 1603, a man named Ravencroft made the first real physical property alteration of glass. Lead oxide was added to the melt mixture which created a new type of glass with a greater refractive index than what the Venetian glass had. This lead glass had better optical characteristics as well being softer and more durable than the Venetian glass.
The English lead glass was known as the finest glass during the eighteenth century. Still today, lead glass is often used for making crystal and artistic objects. The lead glass is usually cut in order to make decorative facets. When cutting glass you grind and polish. When etching glass you can sandblast or use an application of hydrofluoric acid. Gilding can be done with gold paint or gold leaf and uses a low temperature firing in order to permanently affix the metal to the glass.
Few other glass chemistry advances took place until the late nineteenth century. German scientist made large advancements in the alteration of glass composition in order to improve its properties. In 1884 Abbe joined Zeiss and Schott in order to improve glass for optics. They formed the Jena Glassworks of Schott and Sons. This was the beginning of today’s glass making formulas which produced glasses with better optical properties and significantly lower expansion coefficients.
In 1903, the first functional bottle-making machine was invented by a man named Owens. He is referred to as the father of mechanized glass working because of his numerous inventions. In 1912, the Corning Glass Works of New York produced borosilicate glasses which added boron oxide into the melt mixture. They are more resistant to rapidly changing temperatures because they only expand one-third as much as soda glasses when heated.
Fast forward to today’s world, and we have the introduction of smart glass. This type of glass can change its transparency due to various factors. Photochromic glass changes its transparency according to light intensity. Thermochromic glass alters its transparency in response to temperature. Liquid crystal device glass utilizes a thin layer of liquid crystals layered in between two transparent electrical conductors on slim plastic films with the entire package sandwiched between two glass layers. The liquid crystals remain in a random and unaligned state when the power is off. The glass becomes a translucent layer when the crystals scatter light; this obscures direct view.
Electrochromic glass coating usually consists of five layers and is placed on a glass substrate. The electrochromic pile includes thin metallic coatings of nickel or tungsten oxide which is located between two transparent electrical conductors. The application of voltage between the transparent electrical conductors creates an electrical field. Coloration ions are moved by the field reversibly between the ion storage film, into the ion conductor and onto the electrochromic film. This causes the glazing of the glass to switch to a clear and transparent blue-tinted state with no obstruction of view. There is no doubt that glass is constantly evolving into newer and more exciting forms. There are even smart glasses that create an augmented reality and will provide you with text and images hovering above or near what you are looking at. Simply amazing!
The History of Glass
In the 3,500 years since glass was first discovered it has been used to create incredibly stunning and highly practical objects and now forms an essential part of our everyday lives.