How is Glass Made?

The glass container manufacturing process involves a range of procedures, equipment, materials and team members. The key to maintaining optimum control of process quality and productivity is the elimination of any process variation. Below is a step-by-step breakdown of the glass manufacturing process:

Step 1: Glass Melting. The furnace melts cullet (crushed, recycled glass), sand, soda ash, limestone, and other raw materials together. Molten glass usually ranges in temperature between 2,300 and 2,800° F. A Furnace Control Room houses the computer which monitors and controls furnace temperature.

Step 2: Container Forming. The Refiner distributes the molten glass to 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 temperature drops further in the Forming Machine to below 2,100° F. 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 their temperature is brought back up close to the melting point, then reduced gradually to below 900° F. This reheating and slow cooling eliminates the stress in the containers making them stronger and shock resistant.

Step 4: Surface Treatment. The temperature of the containers is reduced to between 225 and 275° F. Cold End Sprays then apply an exterior coating to the bottles to increase line mobility, and reduce abrasions to maintain the inherent strength of the container.

Step 5: Automatic Inspection. The Fast Cooling Section then brings container temperatures down to about 100° F - cool enough to touch by hand. The manufactured containers then pass through a series of instruments that physically and optically test the containers. Rejected containers are recycled back into the furnace.

Step 6: Product Handling & Packaging. A Case Packer then packs the containers in corrugated cases for shipment. The cases are then sent to the Case Palletizer, where they are stacked in a prearranged pattern to increase stability for shipment. 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, depending upon the size of the container. These Bulk loads are also strapped for stability and sent through the Stretch Wrap Unit and covered with plastic wrap for shipment.