Guide to Glass Making
By definition, glass is an amorphous i.e. non-crystalline solid having the properties of being brittle and transparent. Glass today is found in many shapes and forms but the type that is most widely manufactured/used and the one that has been around for centuries is called soda-lime glass.
A Brief History of Glass
Few people might know that glass also occurs naturally with the help of lightning and volcanoes. This kind of glass has been used since the Stone Age across the globe for making tools.
The first manufactured or manmade glass can be traced back to Syria, Mesopotamia or Ancient Egypt. Glass making saw rapid progress during the late Bronze Age in Egypt and Western Asia. Archeologists have discovered colored glass ingots, vessels and ubiquitous beads and by the 15th century BC there was extensive glass production in western Asia, Crete and Egypt. Today glass is manufactured in tons every day.
History of Glass: A Wikipedia article on the history of glass.
Making of Glass: A detailed, technical article on how glass is made.
Recycled Glass: An article on how to make glasses from old soda bottles.
Glass Manufacturing â" Step by step: A detailed article on the process of manufacturing glass.
How to Make Glass
Ingredients used in glass making
Generally speaking, the materials that are used in making glass are classified by chemists into three classes:
- Metallic oxides
There are various types of glass that are manufactured today, however the most common type of glass is made from a mixture of mainly silica combined with small amounts of an alkali e.g. sodium bicarbonate or potash and lime. The alkali helps decrease the glassâ melting point and the lime stabilizes the mixture making the glass stronger and resistant to water.
Glass making: A video of a glass making demonstration at corning museum of glass.
The Process of Glass Making
Glass making is similar to making food, where different ingredients are mixed together.
Glass making begins with combining silica, soda and lime. This is done at a very high temperature. To this mixture are then added other ingredients which help vary the properties of the glass such as color, how reflective it is, the amount of sparkle in it, insulation capabilities, etc.
In addition to the ingredients another aspect that determines the outcome of the glass making process is the way in which the silica/soda/lime mixture is heated, cooled and formed. Generally speaking the silica/soda/lime mixture is heated up to 2,500Â° Fahrenheit for many hours (at times for 24 hours). This produces molten glass (a reddish orange thick liquid) which is then cooled to a temperature permitting work to be done on it. This temperature can be several hundred degrees less.
This molten liquid is then blown, pressed, drawn, rolled, etc. to shape and make glass. Once the liquid has been shaped it is then placed in a âlehrâ oven to be âannealed.â This is done so as to eradicate areas of stress that may appear in the glass. This process results in the glass being strengthened as it is cooled down at controlled temperatures.
Manufacturing of glass: A presentation on how to make glass.
Glass manufacturing process: An article on how to manufacture glass.
Manufacturing float glass: A step by step guide to manufacturing float glass.
Float glass making â" video: A video demonstrating the Float Glass Manufacturing Process.
Categorization of Glass
- Soda Glass: This is the glass type that is most commonly used. Almost 90% of glass manufactured today is soda glass. As discussed above, soda glass is made by mixing silica, soda and lime. This is also the cheapest glass to make but is least resistant to high temperature, sudden temperature changes and chemicals.
- Lead glass: In addition to the basic ingredients lead glass has around 20% lead oxide in it.
- Borosilicate glass: This glass is made to better withstand temperature changes and chemicals. It is comparatively more expensive and contains a minimum of 5% boric oxide.
- Colored glass: Color is given to glass by adding chemicals into the basic glass mix. Different chemicals produce different colored glass. E.g. amber or brown glass gets its color from iron sulphide, iron-chromite creates shades of green and cobalt produces shades of blue.
Insulated Glass Manufacturersâ Alliance: The official website of the Insulating Glass Manufacturers Alliance.
Glass Documentation Website: A site containing documents encompassing all areas of glass for fenestration.
Canadian Glass Association: The official site of the Canadian Glass Association.
American National Glass Association: The official site of the American National Glass Association.
Glass Manufacturing Industry Council: The official site of the Glass Manufacturing Industry Council.
Australian Glass & Glazing Association: The official site of the Australian Glass & Glazing Association.
Australian Glass Industry Report: A market research report on manufacturing of glass and glass products in Australia.
Interesting Facts about Glass
- During the 17th century, glass in Europe became so cheap that the common man started to use it for windowpanes. In addition to providing protection, these windows helped bring light into their houses increasing the level of hygiene by many folds.
- There is a glass making manual that dates back to 650 BCE.
- Glass is transparent because it has a highly random molecular structure. Due to this most of the light passes through it easily.
- Glass is brittle for the same reason that lets light pass through it. The random molecular structure and a non-orderly crystalline structure makes it brittle
- Glass can be recycled 100% and endlessly. Recycling glass does not compromise the glassâs quality, purity and clarity.
- The energy that recycling one glass bottle produces can be used to power a computer for 30 minutes.
- Glass making is similar to making food where you follow a recipe of ingredients, the first three being sand, soda ash and limestone.
- One ton of recycled glass can save 1,300 pounds of sand, 410 pounds of soda ash and 380 pounds of limestone.
- The dynamics of the glass industry have changed with the change in fuel used. Initially when wood was used factories were located near the woods. By 1880, as coal gained popularity glassmaking shifted operations near coal deposits. Now factories are closer to the markets as they burn natural gas.
Guidelines for glass manufacturing: Environmental, health, and safety guidelines for glass manufacturing by the International Finance Corporation (World Bank Group).
Facts about Glass: An article listing some facts about glass.
Interesting facts about glass: An article by The Telegraph listing some interesting facts about glass.
Environmental guidelines for glass manufacturing: A detailed paper detailing guidelines for environmental safety while manufacturing glass.