Corning Glass has a fantastic journal and a huge library of glass
publications, including formulas, methods, etc. I chanced upon iot while
working on mid-to-late 19th century lamp chimneys.

John Dendy

-----Original Message-----
From: George L. Miller [mailto:[log in to unmask]]
Sent: Wednesday, December 18, 2002 9:39 AM
To: [log in to unmask]
Subject: Ghost mold lines from parison and blow molds


Chris Murphy's comment on "ghost" mold numbers in the bottom of jars rings
true.  These "ghosts lines" are commonly found on canning jars that are
clearly mouth-blown.  My guess is that the parison of glass on the blow
pipe  hit the bottom of the mold before the bottle was completely blown.
Then when the bottle or jar is fully blown, the base shifts as the air
pressure pushes the glass against the walls of the mold.  These ghost mold
numbers are from the blow mold which is different from those produced by a
parison mold.

      With machine-made bottles, both semi-automatic and fully automatic
there is a parison mold that forms the glass around the blow pipe.  That
mold has seams, which become compressed when the parison is moved to the
full or blow mold.  In many cases, the parison mold lines are in alignment
with the mold seams of the blow mold, so that the parison mold can not be
distinguished from the blow mold.  The easiest place to see the parison
mold is in the base of the vessel.  It usually is a circle that is slightly
off center of the base.  The Owens scar is from the parison mold and in a
sense is a ghost mold line.  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 does not.  Thus, we can be sure
that a bottle was made on an Owens machine if the scar can be seen, but
there are some bottles that were made by that process where the scar will
not be readily apparent.

      Tony McNichol and I have been expanding our paper on the chronology
of early machine-made bottles and would be interested in knowing about any
published pamphlets and price list data from Owens Bottle Company, Illinois
Glass Company, and Owens-Illinois Glass Company.   We are also interested
in journals from the glass industry.  Any help with this would be greatly
appreciated.

George L. Miller
URS Corporation
561 Cedar Lane
Florence, New Jersey  08518