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Since the beginning of time, people have been fascinated by glass. We collected it. We tooled with it. We decorated it. And, eventually, we molded it into what has become a household essential around the world today: the glass container. Read on to learn more about the glass manufacturing process.

A Brief History of Glass Containers

The first man-molded glass may have appeared around 7,000 B.C. in the form of beaded jewelry made from natural glass such as obsidian, rock crystal, agate, or onyx. It wasn't until 1,500 B.C. that the first glass containers were produced. For thousands of years, glassmakers mixed sand, soda ash and limestone, firing it to extreme temperatures to be blown or cut into useful vessels. Then, the invention of the Mason jar in 1859 enabled the preservation of fruits and vegetables.

Glass containers remained something of a luxury, with the industry dependent on the skill and availability of its glassblowers. In 1903, all that changed with Michael J. Owens' invention of the first completely automatic glass bottle-blowing machine. This machine made it possible to mass produce bottles and jars of uniform height, weight, and capacity. High-speed filling and packing lines soon followed. Glass containers entered the modern age, with today's machines capable of producing over 1,000,000 bottles a day.

The Glass Manufacturing Process      

	Step 1: Glass Melting. The furnace melts cullet (crushed, recycled glass), sand, soda ash, limestone, and other raw materials. A modern glass furnace can reach temperatures of 2,800° F and have a capacity of 300 tons of molten glass.
	Step 2: Container Forming. A Refiner distributes molten glass to an area called the fore hearth, which brings the temperature of the molten glass to a uniform level. A Shearing and Distribution System cuts molten glass from the fore hearth into uniform gobs and sends them to an I.S. (Individual Section) Forming Machine that forces the molten gobs into the mold shape. The glass drops below 2,100° F and formed glass containers leave the machine, crossing a cooling plate where they are cooled rapidly to below 900° F. The glass has now passed from liquid to solid form.
	Step 3: Container Conditioning.The formed containers are loaded into an Annealing Lehr, where they are reheated to nearly the melting point, then cooled gradually. This reheating and slow cooling eliminates internal stress making the containers stronger and more shock resistant.
	Step 4: Surface Treatment. The temperature of the containers is reduced to between 225 and 275° F. Cold End Sprays apply an exterior coating to the bottles to increase line mobility and reduce abrasions. This maintains the inherent strength of the container.
	Step 5: Automatic Inspection. The Fast Cooling Section cools the containers to about 100° F - cool enough to touch. The containers then pass through instruments that perform physical and optical tests. Rejected containers are immediately remelted.
	Step 6: Product Handling & Packaging. A Case Packer packs the containers in corrugated cases. These are sent to a Case Palletizer, where they are stacked in a prearranged pattern for stability. A strapper fits plastic bands around the stacked boxes for added stability and finally, the Stretch Wrap Unit covers the stacked boxes with plastic wrap. Containers can also be sent to a Bulk Palletizer that stacks the individual containers in 5 to 15 layers. Bulk loads are also strapped for stability and sent through the Stretch Wrap Unit before shipping.   For more information about the glass packaging industry, visit the Glass Packaging Institute.