Glass Bottle Production Process

Creating glass bottles can be accomplished through one of two different processes, the blow molding process or the pressing and blow molding process. Each process is chosen based on the type of glass bottle being made. All glass bottles start with raw materials. Silica (sand), soda ash, limestone and crushed glass (recycled glass that can be used in a furnace) are mixed into a specific mixture depending on the desired properties of the bottle. The mixture is then melted in a furnace at high temperatures until it becomes a molten material, ready to be formed.

Glass Forming Method

Molten glass droplets are cut by precisely timed blades to ensure that each glass droplet is of equal weight before it enters the forming machine. The weight of the droplets is important to the forming process of each glass container being manufactured. Molded glass is made by gravity feeding the molten glass droplets into the molding machine where pressure forms the neck and basic shape of the bottle. Once the neck and general glass bottle shape is achieved, this form is called a type blank. To obtain the final container shape, one of two processes is used.

Press and Blow Process

The Press and Blow process is the most common method used in glass bottle manufacturing. It uses an individual section (IS) machine that is divided into different sections to produce multiple containers of the same size at the same time. A shear blade is used to cut the molten glass into specific sized glass pieces. The droplets are dropped into the machine by gravity. A metal plunger is used to push the drop down into the mold, where it begins to form and becomes a billet. The billet is then transferred to the blow mold and reheated so that the billet is soft enough to complete the glass size. Once the billet is reheated to blowing temperature, air is injected to blow mold the container into shape. Press and blow molding methods are commonly used to make wide-mouth and wide-mouthed bottles because their dimensions allow the plunger to enter the form blank.

Blow Molding Process

The blow molding process is used to make narrow containers. It also requires an IS machine where the molten glass block is gravity fed into the mold. The blanks are made by using compressed air to form the neck and the basic bottle shape. The billet is then turned over 180 degrees and reheated, and air is again injected to blow the container into its final shape. Compressed air is again used to blow the bottle into the desired shape. the Blow and Blow method is best suited for glass bottles that require different neck thicknesses.

Finishing Process

Regardless of the process used, once the bottle is fully formed, it is removed from the mold and transferred to the annealing furnace. The annealing furnace reheats the bottle to a temperature of approximately 1,050 degrees Fahrenheit and then gradually cools it to approximately 390 degrees Fahrenheit. This process allows the glass to cool at a uniform rate, removing internal stresses in the glass that could lead to breakage or shattering. The bottles are then carefully inspected to ensure they meet quality control guidelines. Any defective bottles, including bubbles, cracks or misshapen areas, are removed from the line and used as broken glass. All remaining bottles are sorted according to size and type. The bottles are then packaged on pallets and prepared for shipping.

We offer glass bottles for the pharmaceutical industry, if you have any questions about pharmaceutical glass bottles, please feel free to contact us.