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Date: | Tue, 9 Oct 2007 09:09:39 -0400 |
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Jakob,
I do not know of any semi-automatic bottle blowing machines where the
finish was done by hand. All of the semi-automatic and fully automatic
machines that made bottles have a ring mold that creates the finish and
serves as the device for moving the hot parison from the blank mold to the
blow mold. The parison mold contained the amount of glass needed to blow
the bottle and distributes that glass so that it can be evenly blown in the
blow mold. Mold lines from the blank mold are rarely in complete alignment
with the blow mold and this results in what has been called “ghost mold”
lines. It might be better to call them parison mold lines. There are a
couple of things that cause the parison mold lines to be misaligned with
the blow mold lines. One is when the parison is moved from the blank mold
to the blow mold, it is still quite liquid and could be swayed by the
process of moving it. The second is that air jets used to cool molds could
cool one side of the parison which would cause that side of the parison to
expand at a slower rate than the other side thus creating a distortion that
would result in the off-center parison mold line we so often see in the
base of machine-made bottles. The Owens scar is one of the better-known
parison mold lines. It is almost always on the edge of an off-center
circle from the blow mold lines. However, in some cases, when the knife
that cuts the glass off during the gathering process is working well and
the glass is just the right temperature, the base may not have an Owens
scar. I have cataloged two identical bottles with the same mold numbers
and shape where one has a visible Owens scar and the other did not. Thus,
we can be sure that a bottle was made on an Owens machine if the scar can
be seen. It is possible that in rare cases the parison mold could be in
alignment with the blow mold and in such cases, it would be very difficult
to see any parison mold lines.
For a long time archaeologists and collectors have used the mold line
over the rim to identify bottles as being machine-made. These lines can be
burned away when the bottles are fire polished, but that mainly was done
for beverage bottles. If the mold lines stop below the rim it could still
be machine-made. I have not been able to pin down the beginning date for
fire-polished finishes. If there are drag lines from a finishing took,
then I would say that the bottle was mouth-blown.
George L. Miller
URS Corporation
437 High Street
Burlington, New Jersey 08016
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