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"Ghost" seams are usually present on the neck, shoulder, and/or body of the bottle if made by a blow-and-blow machine (like the Owens Automatic Bottle Machine).
These are faint, somewhat wandering, hairline seams which if present (usually) are sporadically visible on the sides of machine-made bottles.
Most machine-made bottles have mold seams about the thickness of a hair while most visible mouth-blown mold seams tend to be several times as thick, higher, but more rounded.
(Mold seam thickness and how high it protrudes [height] is of only moderate use in telling a machine-made bottle from a mouth-blown bottle, though if a bottle fragment has a hair fine mold seam, it is highly likely to be from a machine-made bottle.) 3.
This mark is distinctive to the suction process which feeds glass into the bottom of an Owens machine's parison mold.
(Note: A movie clip showing this process in action is linked at the bottom of this box.) Suction scars can not be produced by feed and flow automatic machines (i.e.
These deviations are discussed on the main Bottle Dating page in a box under 4.The ghost seams are caused by the parison mold parts and if visible enough will be "attached" to the vertical seams in the finish.Click on ghost seam to view a close-up explanatory picture of this attribute.It was noted in 1910 that the Cumberland Glass Company (Bridgeton, NJ) had "...succeeded in perfecting a machine that will satisfactorily produce narrow neck bottles, such as catsups, beer bottles, etc., at a big saving over the hand method." The method used was unusual and may have been unique in bottle-making history: "The machine differs from all others, and in getting the neck upon the bottle, the vessel is made in two sections, the neck being put upon the bowl with a second operation. Manager says machines are fast coming into play in bottle industry, plans eventually to have machines in place of "carrying in boys." Location: Clarksburg, West Virginia" (Library of Congress).This is accomplished so that there is no perceptible mark upon the bottle showing the joint, and the bottle stands every possible test as to strength. Although products of this machine are not conclusively known a bottle such as the one at this link - offset seams shoe polish bottle - may well be a product of the described machine as there is a distinct and abrupt interface edge at the shoulder where the mold seams for both the body and neck end and are offset. This two table semi-automatic machine would have been hand fed with glass (furnace likely to the right) and does have the two different mold sets with the parison molds (where the first "press" part of the cycle took place) the set on the right.