Glass bottles are used to contain a wide range of products, from beer and wine to food ingredients and sauces. They are also used for medication, cosmetics, and essential oils.
Unlike plastic, which is toxic and easily broken, glass is chemically inert and impermeable. This makes it a good choice for products that need to be sterile, or that are exposed to more corrosive materials. It is also a great way to protect your contents, because glass does not allow oxygen to get into the liquids in the bottle.
The manufacturing process for glass bottles begins when sand, limestone, and other raw materials are mixed with furnace-ready recycled glass called “cullet.” After a certain amount of time passes, the cullet is then cooled and mixed into molten glass.
While the exact proportions of glass in a finished bottle depend on what it’s intended for, cullet typically accounts for 15 to 50 percent of the final product. The remaining glass is melted and shaped into bottles or jars.
Once a bottle is made, it’s subjected to inspection by quality control staff. Any bottles that show signs of rust, cracks, or other imperfections are discarded.
The rest of the bottles are sent for a final quality check before being packaged and delivered to grocery stores, restaurants, hotels, and other retailers. If they pass this inspection, they are sorted and separated by colour and small contaminants removed using optical technology.
This process allows for bottles that have passed inspection to be repurposed. They are then reused for other products, such as tiles and filtration.
After a bottle has passed this final inspection, it is transferred to the annealing lehr, where the bottles are heated and gradually cooled until they reach an even temperature that prevents internal stresses from causing them to break or shatter.
The lehr can reheat a bottle’s contents to as high as 1,600 degrees Fahrenheit, and it can cool the glass to about 900 degrees F. This temperature range is necessary to maintain the glass’s integrity and avoid cracking or breaking during shipping and storage.
Eventually, the bottles are loaded into a blowing machine. Blown-glass bottles can be produced in three different processes:
Press and Blow Process – a plunger is inserted first, then air is added to form a gob into a parison. This method is often used to create bottles with wide mouths, though it can be used for narrow-mouth applications as well.
Conditioning – the bottles are reheated to 1500 degrees Fahrenheit, and gradually cooled down to about 390 degrees F. This method can eliminate stresses in the bottle that might cause it to break or break into pieces during shipping and storage, and it can also help the bottles retain their shape while traveling on a ship.
Some glass manufacturers use special coatings on their bottles to make them break less easily. Walter Himelstein, a former beverage industry executive, invented these coatings to make glass bottles less likely to break or leak, and to make them more durable.