Glass

Glass is a non-crystalline and amorphous solid, whereas, at the atomic level, it is actually a supercooled fluid. It can often be transparent. Glass has widespread use in the fields of tableware, packaging, optics, laboratories, art, and architecture.

Glass is a homogenous mixture of silicates of various alkaline metals of non-crystalline and transparent or less transparent substances. There are various types of glass depending on its use, such as photochromatic, pyrex, Xena, quartz, crown, and flint glass. 

Ordinary glass is produced from a batch of various raw materials like silica, bleaching powder, oxides of alkaline metals, calcium oxide, etc. The use and manufacture of glass date back to the Egyptian and Mesopotamian civilizations. Glass is generally manufactured by supercooling of a liquid. Although glass is a supercooled liquid, it displays all the characteristics of a solid. In this article, we will talk about various types of glass, their composition and their uses. 

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Manufacturing of Glass 

The manufacturing process is mainly laid down in four steps. In the first step, the batch is prepared by accumulating all the raw materials. The main components consist of silica sand, calcium oxide, magnesium, etc. These are weighed and mixed with recycled glass. This recycled glass is also known as a cullet. It significantly reduces the consumption of energy. In the second step, the batch is passed into a five-chambered furnace from a mixing silo. The temperature of the furnace may be up to 1600 degrees celsius.

The third step consists of a float bath. The molten glass is then "floated" onto a bath of molten tin at a temperature of about 1000°C. It forms a “ribbon”, which is normally between 5 and 6 mm. The optimum ribbon thickness can be obtained by the roll machines. In the final step, the molten glass at 600 degrees celsius is passed into an annealing chamber called a lehr. After annealing, the glass is cut and modified into the desired shape for specific use. 

For the manufacturing of coloured glasses, a few substances, such as cobalt oxide, cupric oxide, etc., are added into the batch as per the required colour. These substances are essential for the manufacturing of colourful glass.

Types of Glass and Their Composition 

There are various types of glass based on their uses and composition. Let us take a look at some of them.

• Water Glass: Just like the name, it is soluble in water and is manufactured from sodium silicate.

• Photochromic glass: This is a special type of glass that turns black in sharp shining light; thus, such glasses are used as a light protector. It relieves the eyes and is utilized in making eye lenses and goggles. The main reason for such glasses being black or photochromic glasses is the presence of silver iodide.

• Pyrex glass: It is also known as borosilicate glass. It has specific characteristics of chemical durability. Pyrex glass also has more thermal unmalleable resistance power.

• Lead crystal glass: This is a special type of glass that is used in making various ornamental items. In fact, on cutting lead crystal glasses, the optical phenomenon of total internal reflection takes place very sharply. As a result, a dazzling light is produced.

• Soda glass: It is also known as soft glass. It is brittle and is the cheapest and most commonly existing type of glass. This can be broken by the alternation of temperature.

• Xena Glass: It is the best-known form of glass. Chemical containers and equipment for scientific experiments and research are manufactured. This glass is composed of zinc and barium borosilicate.

• Flint Glass: It is produced from sodium, potassium, and lead silicate. Such glasses are also used in making electric bulbs, lenses of telescopes, microscopes, cameras, and prisms, etc.

• Crown glass: It is frequently used in making lenses of eyeglasses. This is a soda-lime-silica glass.

• Crookes glass: In this glass, cerium oxide (CiO2) is present, which absorbs the ultraviolet rays from the sunlight. It is used in making lenses of spectacles.

• Quartz glass: This is also known as silica glass because it is obtained by melting silica. Ultraviolet rays emerge through it. Quartz glass is used in bulbs of ultraviolet lamps, containers of chemical reagents, laboratories apparatus, etc.

Colourful Glass

During the manufacturing of glass, some extraneous substances are added in the molten or the fused state. These substances are generally various metallic oxides. These metallic oxides impart colour to the glasses, making them colourful. Cobalt oxide and cupric salt, on the other hand, impart a deep blue and peacock blue shade to the glass, respectively. The shades of red colour are imparted from Gold Chloride or Purple of Cassius, Cadmium Sulphide, Cuprous Oxide, cuprous salts, and Selenium Oxide.

Cadmium sulfide, Ferric Salt or Sodium Uranet are used to impart yellow colour. Manganese dioxide displays a significant array of colours from blue to light orange. Carbon imparts a blackish colour when added with molten glass. All these additional metallic oxides make the glass colourful. They are generally added during the selection of the batch as per the colour requirements.

Uses of Glass 

Owing to its transparency and easy to mould characteristics, glass has a variety of uses. It is used extensively in tableware, architecture, packaging, laboratories, optics, and art. 

• As tableware - Glass is usually used as tableware in the form of drinking glasses, jugs, decanters, bowls, and other utensils.

• In packaging - Glass is inert, and its impermeable nature makes it a good packaging material. It also has high chemical durability against water. Moreover, glass packaging is sustainable, recyclable, reusable, and refillable. That's why glass packaging is so extensively used for storing food and beverages.

• In Laboratories - All the laboratory apparatus are made with glass since it is chemically inert in nature. Also, reusability is another factor behind the use of glass for apparatus. From test tubes to burettes to pipettes, every apparatus you see in a lab is made from glass.

• In optics - Lenses of eyeglasses or spectacles are made using glass only. Recently fibreglass is being extensively used in the optical industry.

• In architecture - The most common example is the windows. Moreover, sheet glasses with electrochromic coating are used for various architectural masterpieces and buildings. 

Did You Know?

• The obsidian glass was used during the stone age owing to its fractured edges, which made it ideal for cutting tools and weapons.

• The term 'glass’ was coined during the late Roman empire from a Latin word “, Glesum” meaning a transparent and lustrous substance.

• At the atomic level, glass is regarded as a supercooled liquid. But on the other hand, it displays all the mechanical properties of a solid.