Colorful glass bottle

Glass – In its pure form, glass is a transparent, relatively strong, hard-wearing, essentially inert, and biologically inactive material which can be formed with very smooth and impervious surfaces. These desirable properties lead to a great many uses of glass. Glass is, however, brittle and will break into sharp shards. These properties can be modified, or even changed entirely, with the addition of other compounds or heat treatment.

Is Glass Solid? – Looking at glass molecules under very low temperatures, they found that the molecules do appear to eventually form into solid geometrical shapes. Glass becomes solid eventually

Common glass is mostly amorphous silicon dioxide (SiO2), which is the same chemical compound found in quartz, or in its polycrystalline form, sand.

  • windows – churches
  • plates, bowls, drinking
  • telescope – astronomy
  • microscope – biology, microbiology
  • non-reactive labware – chemistry

Glass fiber – a material consisting of numerous extremely fine fibers of glass. Glass fibre is commonly used as an insulating material. It is also used as a reinforcing agent for many polymer products; to form a very strong and light fibre-reinforced polymer (FRP) composite material called glass-reinforced plastic (GRP), popularly known as “fiberglass”.

Early American Pattern Glass (EAPG), also known as pressed glass, was produced from roughly 1850 to 1910. Cheaper to manufacture than blown glass, this glassware was made in cast-iron molds

Cut glass is glass that has been decorated entirely by hand by use of rotating wheels. Cuts are made in an otherwise completely smooth surface of the glass by artisans holding and moving the piece against various sized metal or stone wheels, to produce a predetermined pleasing pattern.

American Brilliant Cut Glass – produced between 1876 and 1914. leaded-crystal goblets, tumblers, decanters, and serving plates, each of which had been deeply cut by hand on a succession of metal, stone, and wooden wheels.

What’s the problem?
Glass is good for making windows for cars. It is clear, strong and can be shaped to fit snuggly into the car body. However, in its basic form, if it breaks, glass shatters in to very sharp pointed pieces. That’s a problem. Unfortunately, cars and their passengers bump into things and causes the windows to break. To prevent occupants from being injured by the broken glass, engineers came up with a better solution.

  • Ask – Glass has many desirable properties. The sharp pointed shards of broken glass are a safety hazard. What be less dangerous than these sharp pieces?
  • Imagine – In general, small cubes would be less dangerous than sharp pointed pieces. How can glass be modified so it breaks into chunks?
  • Design, Build – Glass can be manufactured to have these properties. Safety glass is tempered by heating it above its annealing point of 600 degrees, then rapidly cooled, causing it to harden and contract. This causes compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass.
  • Improve – New materials are being developed to make even better car windows.

That’s engineering

  • surface tension – a property of the surface of a liquid that causes it to behave as an elastic sheet.
  • tensile stress (or tension) – the stress state leading to expansion (volume and/or length of a material tends to increase). Tensile stress is induced by pulling forces across a bar, specimen etc.
  • compressive stress – the stress applied to materials resulting in their compaction (decrease of volume). When a material is subjected to compressive stress then this material is under compression. Usually compressive stress applied to bars, columns, etc. leads to shortening.

Engineering ideas

  • transparent, inert, biologically inactive, smooth, impervious, surface, brittle, amorphous silicon dioxide (SiO2)

Do It
Challenges for you to work on…

  • Find some examples of glass being used in unusual ways. What properties of glass are important for this use? What other materials are used in this way?

Learn more…