Glass Packaging Institute the glass finish number. For example, an 8-425 finish is approximately 8 mm neck outside diameter with a 425 finish corresponding to a threaded neck typically found on small vials. Glass Packaging Institute The Glass Packaging Institute (GPI) is the North American trade association for the glass container industry, headquartered in Arlington, Virginia. Through GPI, glass container manufacturers advocate job preservation and industry standards, and promote sound energy, environmental, and recycling policies. The GPI membership consists of 5 glass container manufacturing member companies, and 33 supplier member companies, who provide raw materials, recycled glass, equipment, decorating, and other services to
Glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish. Container glass for common bottles and jars is formed by blowing and pressing methods. This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance. Further glass forming techniques are summarized in the table . Once the desired form is obtained, glass is usually annealed for the removal of stresses and to increase the glass's hardness and durability. Surface treatments, coatings or lamination may follow to improve the chemical durability