Glass at a Glance
In the most simplistic terms, glass is liquid sand reformed into to a transparent “solid”. The chemical process of creating glass is undergone by heating quartz sand, also known as silica sand, to temperatures above 3,090 degrees Fahrenheit until it melts into a clear liquid. Once the sand is in liquid form, it is cooled and undergoes a transformation that doesn’t allow it to fully turn to a solid. Instead, the cooled sand acts as a frozen liquid in a state known as an amorphous solid, which is a mix between a solid and liquid. The result is no longer the opaque, yellow colored sand, but the transparent pane we know as glass.
How is Glass Made?
Start with Quartz Sand, Soda Ash, and Limestone
As stated above, glass starts with what’s known as quartz and/or silica sand. The first step in creating glass is mixing this quartz sand with soda ash (sodium carbonate) and limestone (calcium carbonate). Other additions can be added, depending on the end purpose or color of the glass.
Heat the Compound
After mixing the three primary ingredients (and any others needed), the compound is placed in a heat resistant crucible, or holder. Once in the crucible, it is placed into a furnace and heated to the 3,090 degrees necessary to melt the sand. Once the mix has melted, it is now considered molten glass.
Stir the Molten Glass
To remove bubbles from the final product, the molten glass must be stirred to create a consistent thickness throughout. Other chemicals such as sodium sulfate are often added to help with this process.
Mold the Molten Glass
The next step in creating the transparent final product we know as glass is the cooling process. There are two ways this can be done. This first is by placing the molten glass into a mold to let it cool. This is often how lenses and other simply shaped glass items are made today. The second, often used by commercial producers, is by placing the molten glass into a bath of molten tin and shaping it with pressurized nitrogen. This method creates float glass and has been used since the 50s to create panes of glass.
While the glass could theoretically be done after the prior step, there is one more crucial step added to help glass maintain its strength over time. In a process called annealing, the glass is placed into a kiln, or oven, between temperatures of 750 and 1,000 degrees Fahrenheit. This removes any and all stress points that may have formed during the cooling process and readies the glass for its final use.
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