ABSTRACT
A finish refers to the particular shape of the lip and neck of a vessel. The closure and finish of a container must fit closely to permit hermetic seals. Screw designs were adopted for other late nineteenth century industries where hermetic seals were not a factor. Officially approved by the Glass Container Association (GCA) was for the deep thread screw finish, adopted on October 29, 1920. Other standardized screw finishes, both deep and shallow, followed shortly thereafter, so that 1921 may be used as the beginning date of manufacture for what came to be known as the Continuous Thread finish, or computed tompgraphy( CT) finish for short. The earliest widespread finish for vacuum/friction caps appears in the late nineteenth century. The friction finish is still commonly used with vacuum closures, and thus has an extremely long span of production, from 1905 to the present.
