Glass – it's everywhere: our homes, our cars, and where we work. While we see this amazing material all around us every day, in its purest form it’s virtually invisible. Wondering exactly how glass is made? Let’s start at the beginning.
Glass starts out as billions and billions of tiny grains of sand. While unremarkable in appearance, inside this silica-rich mineral composition is the key to a remarkable transformation. First, a combination of soda ash and lime – A.K.A. sodium bicarbonate and calcium bicarbonate – are mixed with bits of crushed glass, or cullet, to create what we call “the batch.”
The batch moves along the conveyor into the charging end of the melting furnace, and that’s when things really start to heat up. Superheated air is combined with jet streams of natural gas, creating a torch-like blast of flame with temperatures reaching a staggering 4500 degrees Fahrenheit. Chemical reactions and the extreme heat inside the liquified mixture help eliminate bubbles as the molten mixture continues its three-day, one-quarter-mile journey.
To make glass worth looking through, the finished product must have two very important features: it must be bubble-free and perfectly flat. To make perfectly flat glass, you need a perfectly flat surface – that's where tin comes in. Flat panes of glass are formed by pouring the molten mixture on top of a river of melted tin. The lower density of the tin allows the glass to float on top while the undisturbed surface of the liquid tin creates a flawlessly flat surface and is why this process is referred to as “float glass.”
A series of wheels called “stretch machines” alter the glass to the desired thickness and width. Once it’s spread out, the annealing process begins. Annealing is where the glass is slowly cooled over a period of time, which helps make it stronger and more durable.
As the glass moves along the annealing lehr, it is slowly cooled from over 2,000 degrees to a brisk 1,000 degrees and continues to solidify. Once the glass is cooled and hard enough to be removed from the tin, the long, continuous sheet is further cooled by open-air fans to around 200 degrees.
Next, carbide cutting wheels score the glass to form uniform pieces. The ribbon of cooled glass passes over roller wheels that act as fulcrums, making a clean break along the scored lines. Then the uniformly cut pieces are removed from the main line by an automatic machine known as the vacuum transfer module (VTM), which literally sucks the panes off the conveyor and transfers them to a stack.
Each batch is finished to a desired thickness and cut to sizes ranging from 96 to 240 inches before being sorted and stacked and moving on to finishing. From there, some of the glass moves into the magnetic sputtered vacuum deposition chamber (MSVD) process, where microscopic coatings are bonded to the glass. These coatings contain thin layers of various metals, primarily silver, which are bonded to the glass for solar control as well as other specialized applications. Then, it’s off to shipping.
There you have it – the story of glass, from raw materials to the transparent marvels that shape our world. Vitro Glass proudly manufactures around four million square feet of glass every day, operating 24 hours a day, seven days a week and 365 days a year.
For more information about how glass is made or any other questions related to glass, please contact Vitro glass or call 1-855-VTRO-GLS (1-855-887-6457).
Updated on November 22, 2024
