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Creating glass containers can be accomplished by one of two different processes – the Blow and Blow, or the Press and Blow process. Each process is chosen based on the kind of glass bottle being made. All glass bottles start out as raw materials. Silica (sand), soda ash, limestone, and cullet (furnace-ready, recycled glass) are combined into a specific mixture based on the desired properties of the bottle. The mixture is then melted at high temperatures in the furnace until it becomes a molten material, ready for formation. The type of glass this mixture will produce is known as soda-lime glass, the most popular glass for food and beverages.
Glass Forming Methods
Molten glass gobs are cut by a perfectly-timed blade to ensure each gob is of equal weight before it goes into the forming machine. The weight of a gob is important to the formation process for each glass container being made. The molded glass is created by gravity feeding gobs of molten glass into a forming machine, where pressure forms the neck and basic shape of the bottle. Once the neck finish and the general glass bottle shape has been achieved, the form is known as a parison. To achieve the final container shape, one of two processes are used.
Press and Blow Process
The Press and Blow process is the most commonly used method in glass bottle manufacturing. It uses an individual section (IS) machine, which is separated into varying sections to produce several containers of the same size simultaneously. The molten glass is cut with a shearing blade into a specific gob size. The gob falls into the machine by force of gravity. A metal plunger is used to push the gob down into the mold, where it starts to take shape and become a parison. The parison is then transferred into the blow mold and reheated so that the parison is soft enough to finish off the dimensions of the glass. Once the parison is reheated to blowing temperature, air is injected to blow the container into shape. Press and blow methods are typically used for manufacturing wide-mouth bottles and glass jars as their size allows the plunger into the parison.
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