That Coke bottle in your hand started as a pile of sand. Ancient Egyptians came up with the glass recipe mixing sand with lime and soda, and current glass-making recipes typically use 80 percent silica mixed with 10 percent lime and 10 percent calcium oxide. Egyptians, however, lacked our advanced recycling methods and machinery that helps keep our earth greener and cleaner.
Sand to Bottle
To become a bottle, the sand mixture goes through a series of procedures, starting with the hot end processes where molten glass is shaped. Step one is enhancing the sand mixture with a dose of recycled glass along with various other components. These usually include ferric oxide, aluminum oxide, barium oxide, magnesia and sulfur trioxide.
Next up is the feeding the mixture into a flaming furnace, where temperatures can hit as high as 1675 degrees Fahrenheit. Once the mixture hits what is known as its plastic stage, a shearing blade cuts and shapes the glass into a cylinder shape known as a gob. The gobs go rolling down a ramp that feeds them into an individual section machine, aka an IS machine.
The IS machine is outfitted with anywhere from five to 20 sections that sport identical molds, resulting in five to 20 glass bottles all being produced simultaneously. Once the gobs are all in place, metal plungers press each gob into the individual molds, producing what is known as a parison. The parisons each ramble on over to one more mold, where they are blown into their final shape.
The final phases are annealing and the cold end processes. Annealing is an optional process that consists of reheating bottles to combat weak points created by uneven cooling rates. The cold end processes include inspection and packaging.
Bottles as Recycled Glass Products
Empty Coke bottles usually go into a catch-all type of recycling bin where they’re picked up and hauled to the recycling plant. If the recycling plant is stuck in the ancient Egyptian era, someone may have to manually sort out the glass, paper, plastics and all other contents by hand. More advanced plants used automated sorting machines that can not only divvy up the different types of recycling products, but can tell the difference between construction waste (C&D), manufacturer waste (MFR), and municipal solid waste (MSW).
Such machines, like General Kinematics Multi-Stream Recycling Systems, can first divide the waste categories onto their appointed conveyer belts. They then employ high-tech screeners that can separate out recycled glass products and other items, along with a vibratory fines screen and an air classifier to ensure the right material gets to the right place.
The right place for recycled glass products is an area where they are crushed into a substance called cullet. The cullet makes its way to the bottle manufacturing plant, where it’s added to the sand mixture to take yet another round as part of a new Coke bottle. Thanks to the ability to retain its quality, glass can be crushed, melted and reshaped nearly indefinitely.
Image By Hariadhi [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0], via Wikimedia Commons
