A Window Into The Glass Making Process
Written by: Bill Herren
Glass is used to make countless products including bottles, windows, art, dishes, and more. Not all glass is the same; there are many different types that are used for different purposes. The most common type of glass is soda lime glass. It contains silica, which gives the glass its’ transparent appearance. The process of making glass depends on the type of glass being produced. The following information will outline the process of how soda lime glass is made.
How Soda Lime Glass is Made
In order to make glass, you need to gather the raw materials. Soda lime glass is made with sand, soda ash, limestone, and a material called dolomite. These things are melted together to eventually form the material we think of when we hear the word glass. The first step in producing glass after gathering materials is ensuring that all of the materials are pure and high quality. These materials are then mixed, and put in a melting furnace. The furnace works to melt the raw materials and is used to change the properties of the finished product depending on what is being produced. Once the raw materials have gone through the furnace and have been melted together, any necessary coatings are applied. Coatings can include energy efficient materials and hard coatings. The glass is then fed into something called a float bath to make it optically flat. At this point something called an annealing lehr is using to remove stresses in the glass while also carefully cooling it down. The glass is then inspected for quality and continues on to be cut into the correct shape so it can be shipped to the customer.
What is Silica?
Silica is the material that gives glass its transparency. Silicate glass includes soda lime glass, window glass, and fused silica glass among others. Silica is the common fundamental constituent of glass and is most often found in nature as quartz. Other substances are generally added to silica during the manufacturing process in order to simplify processing. There are a few different types of silica glass.
- Fused Silica Glass – Fused silica glass is very hard, has a low thermal expansion, and is resistant to very high temperatures. It is also resistant to weathering. Fused silica glass is most often used for high temperature applications such as making furnace tubes.
- Soda Lime Silica Glass – Soda lime silica glass is most often used to make items such as windows, and light bulbs. Because it is transparent, and can easily be formed, it is the most common type of window glass. Soda lime silica glass has a high thermal expansion and is not very resistant to heat.
- Sodium Borosilicate Glass – One well known example of a borosilicate glass is Pyrex. Sodium borosilicate glass can stand heat expansion much better than soda lime silica glass and is much more dimensionally stable. Because sodium borosilicate glass is less likely to crack under thermal shock, it is used to make items such as household cookware, and reagent bottles.
Additional types of silica glass include lead-oxide glass, which is used to make crystal glass, aluminosilicate glass, which is used pretty extensively for fiberglass, and oxide glass, which is oftentimes used in fiber optics. During the glass making process, various materials can be added to change the color and other properties of glass to make it suited to its future application. To learn more about the process of glass making, and the different types of glass, consult the following resources.
Further Resources on Glass Making:
- All About Glass – An article explaining what glass is and how it is made from the British Glass Manufacturers’ Confederation.
- How Glass is Made: From The Batch House to the Lair – A great article and video explaining the process of making glass and the different steps of manufacturing.
- Physical Properties of Glass – Information on some of the physical properties of some common types of glass.
- How is Pyrex Glass Made? – An article explaining the process of making Pyrex glass, commonly used in household cookware.
- How Flat Glass For Windows is Made – A video from the BBC that explains how the flat glass used for windows is manufactured.
- How is Glass Made? – A scientist explains how exactly glass is made and what is used in the process.
- Smart Glass for Energy Efficient Windows – An article from the Royal Society of Chemistry about smart glass, a product that could be introduced in the future to help with energy efficiency.
- Raw Materials Used to Make Glass – A kid friendly page that explains some of the different raw materials used to make glass.
- Silica Glass – A great article explaining how silica is formed and what it is used for, data sheets and guides available as well.
- How Glass Was Made in the Ancient World – An article explaining how glass was manufactured all the way back in ancient Roman times.
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