Overview of Glass Industry

Glass is one of the most versatile materials used not just in many industries but also in daily life.  Glass has many uses because of its transparency, high resistance to chemical attack, effectiveness as insulator, ability to contain a vacuum and many other properties. Glass is also one of the oldest materials in the world. Archaeologists have found evidence of man-made glass in Egypt which dates back to 6000BC. On the other hand, flat glass was mentioned as early as 290 A.D. (Shreve & Brink Jr., 1977)

Glassworks in the United States were founded in 1608. The first glass rolling process dates back to 1688 in France. Joseph Paxton's Crystal Palace at the Great Exhibition of 1851 marked the beginning of the discovery of glass as a building material. The revolutionary new building encouraged the use of glass in public, domestic and horticultural architecture. However, glass back then was very expensive because it was considered an art with closely guarded secret formulas and empirical processes of manufacturer based from rule of thumb and experience.  It was not until the beginning of the 19^th century that glass has become relatively cheaper made possible by the invention of machine process that can mass produce glass. The invention of the first bottle machine in 1904 by Owens also marked the rapid developments of machine processes for glass production. In 1952, Sir Alastair Pilkington invented the float process that greatly reduced the laborious work of flat glass production. Before the development of float process, larger sheets of plate glass were made by casting a large puddle of glass on an iron surface, and then grinding and polishing both sides for smoothness and clarity - a very expensive process.

From 19^th century onwards, scientists and engineers enter the field with increasing numbers and new products appear as a result of intensive research.  Today, glass making is a modern, hi-tech industry operating in a fiercely competitive global market employing all the tools of modern science and engineering in the production, control and development of its many products.

Nowadays, in general, commercial glass products fall into numerous classes according to composition:

1.     Fused Silica or vitreous silica. This class of glass is made from high-temperature pyrolysis of silicon tetrachloride. It has high chemical and thermal resistance because of its low expansion and a high softening point. This kind of glass is also extraordinary transparent to ultraviolet radiation.

2.     Alkali Silicates. They are the only two-component glasses of commercial importance. These are soluble glasses used in solutions. This glass type is widely used as an adhesive for paper in the manufacture of corrugated-paper boxes.

3.     Soda-lime glass. The soda-lime-silica represents by far the largest percentage of glass made today. It is used for windows, transparent fixtures, and containers of all kinds.

4.     Lead Glass. Commonly known as lead crystal, lead glass is used to make a wide variety of decorative glass object. It is made by using lead oxide instead of calcium oxide, and potassium oxide instead of all or most of the sodium oxide. It has also great importance in optical work because of its high index of refraction and high dispersion.

5.     Borosilicate Glass. It is made mainly of silica and boric oxide with smaller amounts of the alkalis (sodium and potassium oxides) and aluminum oxide. This type of glass has relatively low alkali content and consequently has excellent chemical durability and thermal shock resistance. As a result, it has many diversified applications.

6.     Special glasses. Other types of glasses not mentioned above fall under special glasses. It includes glass fibers used for reinforcement, optical glass used in scientific instruments, sealing glass used to protect metals, technical glass used in electronics and many more types used in emerging industries.