Glass By: Mario Popoli Augusto González

DefinitionPropertiesAdvantagesDisadvantagesHistoryUses Uses in architecture

So… you thought glass was boring right? was boring right?

Definition

Glass is a hard, brittle substance made by fusing silicates with soda or potash, lime, and, sometimes, various metallic oxides into a molten mass that is cooled rapidly to prevent crystallization or annealed to eliminate stresses: various types of glass can be transparent, translucent, heat- resistant, flexible, shatterproof, photochromic, etc. Glass generally refers to a hard, brittle, transparent amorphous solid, such as that used for windows, many bottles, eyewear, and so on.

Origin

Before man learned the secret of glassmaking, nature was the world's only glassmaker. Lightning striking sand melted it into long, thin tubes of glass, and volcanoes erupting melted rocks and sand into glass.

Today, three inexpensive ingredients, sand, soda ash, and lime, are melted together to make glass. This is done in large furnaces at high temperatures until the mixture become a syrupy mass. When this syrup cools, it is glass.

Methods

When glass is in a melted state, it can be shaped by many methods, but the most common are blowing, pressing, and drawing.

Blowing

Blowing is the oldest method of working with glass, dating back thousands of years. A ball of molten, or melted, glass is put on the end of a hollow iron pipe, and a worker blows gentle into the pipe (much like the way you blow soap bubbles) until the glass takes the shape and thinness the blower wants. During this process, the glass is constantly reheated to keep it soft and workable. When the glass is shaped to the blower's satisfaction into a bottle or a vase, it is broken from the pipe. Although glass blowing by hand is still done today, it can also be done by machine.

Pressing

In the pressing method, a hot glob of glass is dropped into a mold, then pressed with a tool, so the glass fills the inside of the mold. Ashrays, baking dishes, and glass containers are made this way.

Drawing

The drawing method shapes glass flat, as for windows and mirrors, or into tubes, as for fluorescent lights, TV tubes, and laboratory equipment. To make flat glass, first the melted glass is drawn into a tank of melted tin. The tin's perfectly smooth surface forms a smooth layer of glass as the glass floats on top of the tin. To make glass tubing, a stream of molten glass is drawn around the inside of a cylinder. As the cylinder rotates, air is blown through it, forming a continuous tube out of the glass.

No matter which method is used, the glass must still go through a process called annealing. In annealing, the glass is reheated. Tempering is also used to strengthen glass. In tempering, the glass is reheated, then chilled by sudden blasts of cold air. Banks, tanks, aircraft, and some government cars have glass so thick and with so many layers that it can stop a bullet even at close range!

Lamp working

This process should not be confused with another method called lamp working, in which finished glass tubes are heated over a blowtorch, and as the glass worker bends, twists, and stretches the glass, he can create miniature animals, ships, and baskets.

Properties

The properties of glass are varied by adding other substances, commonly in the form of oxides: lead, for brilliance and weight; boron, for thermal and electrical resistance; barium, to increase the refractive index, as in optical glass; cerium, to absorb infrared rays; metallic oxides, to impart color; and manganese, for decolorizing.

Advantages

Advantages Excellent abrasion resistance Resistant to chemicals, solvents, oil, grease No problem with UV degradation Stable over a wide range of temperature Easily cleaned Long life product Looks good Transparency Price

Disadvantages

Disadvantages Delicate and heavy Doesn’t work as a structural material Not very robust Shatters easily when stressed, Solar heat penetrates it Transparency Price