Glass Forming

Though there are a several ways that glass can be processed to make different products, there are two very distinct methods that have been practiced for many years - glass forming and glass molding. Of the two, glass forming has been used for hundreds of years. In very simple terms, it is taking a bubble of molten heated glass and blowing into it to form a drinking glass, vase, or pitcher. Read More…

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In the modern era, glass forming, formally known as glassblowing, has become a very technical process involving complex machinery and equipment. Though heated molten glass stands at the center of this form of glass production, the shaping of it has been improved to the point of being able to make hundreds of glass products in a very short amount of time.

Glass comes in three different forms – soda lime, borosilicate, and phosphate. The two types that are used in glass forming are soda lime and borosilicate. Phosphate glass is a specialty product produced for industrial and scientific use. The type of glass we most commonly see is soda lime, which is the type that is made from silica sand. Borosilicate is used in glass forming to make cookware and heat resistant materials. Regardless of whether the glass is soda lime or borosilicate, the forming process is the same.

Glass forming begins with the combining of the raw materials. Soda lime glass is a combination of silica or sand, soda or sodium oxide, and lime or calcium oxide. When mixed, the largest amount, or 70%, of the mixture is silica. Soda is added to lower the melting temperature of the molten mix while lime stabilizes it. The mixing and heating is done in the batch housing where each step is carefully monitored and controlled.

Once the mixture is completed and molten, it moves to the production center where it will be formed into different products. The production center consists of a set of molds. The batches from the batch housing are cut into little equal sized pieces called gobs. They are trimmed to the exact size needed for the product being produced. The gob has a puff of air forced into it to shape the parison, which is placed into the mold where it receives a stronger burst of air that forces it against the sides of the mold. Once formed, the molded product is allowed to cool before being moved to the finishing room.

The fully molded product is initially coated with a thin layer of metal and takes on the appearance of the finished product. When molded items cool, the outside that is exposed to the air cools faster than the inside creating an unevenness to the glass.

As with metal molds, glass is annealed, a process where the glass is heated and cooled multiple times until the inside and outside temperatures match.

The final stage of the process is the application of a polymer bath designed to give the exterior of the product a shiny finish and make it scratch resistant, increase its durability and strengthen it.

When glass has completed its use, it can be returned to a recycling center to be taken back to the production facility to be used in the creation of new glass products.