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Feature #7 describes a couple glass related features that are quite consistent in machine-made bottles, but not diagnostic, i.e., mouth-blown bottles may sometimes have few/no bubbles in the glass and even thickness.
(Note: the term "parison mold" and "blank mold" are synonymous for the first mold in the two mold machine process.): (see the Note box below point #3 for an exception) run up to the highest point of the finish and often onto the extreme top finish surface (i.e., onto the rim or lip).
Both seams are quite diagnostic of machine manufacture and are usually visible, though the seam at the top of the finish can be hard to see on some bottles - especially if the finish was fire polished.Antique and vintage glassware encompasses countless types of decorative-yet-functional containers, bowls, and platters produced from the late 1800s through the mid-1900s.While some collectors of antique glass purchase these delicate objects for display purposes only, others buy vintage glassware to use for cooking and serving.See the machine-made section of the Bottle Bases page for more information on these scars. with distinct suction scars were likely Owens machine produced.)6. Machine-made bottles tend to have few if any bubbles in the glass and the thickness of the glass is usually more uniform throughout the bottle as compared to mouth-blown bottles.(Note: It is likely that other types of suction based automatic bottle machines made in Europe in the 1920s - and possibly later - also produced a suction scar on the base of their products [Pearson 1928]. The presence of a circular valve mark on the base of a bottle (typically a wide mouth bottle or jar) is sure evidence of machine-made manufacture by a press-and-blow machine. This is especially true of later machine made bottles, i.e. (Note: The presence or absence of bubbles in the glass and relatively even distribution of the glass throughout the characteristic is not a primary feature of either machine-made or mouth-blown bottles, though there are strong trends.