d. Gray Area. A gray area is usually found in pressure breaks. The area of
transition between the origin and the appearance of other markings may be mirrorlike,
especially if the speed of breaking is at a slow rate at that time. The gray area is the
zone of accelerated speed of the break. If the break is uniform, the rough area may not
e. Percussion Cones. These marks are characteristics of impact breaks and
indicate the point of origin of the impact. If a perfect cone is formed, the break followed
the formation of the cone; if there is no cone, the break occurred as the cone was
f. Featureless Surfaces. These surfaces are occasionally seen and are
characteristic of thermal shock breaks. They indicate that the break occurred slowly
and with little violence.
2-17. GLASS CONTAINER DEFECTS
A list of common glass container defects follow:
a. Chip. A chip is an area where glass has been broken off, but the bottom or
body wall is not materially weakened. It is a minor defect.
b. Stone in Glass. This defect has the appearance of a lump in the glass. It is
an unmelted opaque material imbedded in the glass. It is a minor defect.
c. Pitted Area. This refers to small indentations or pits which are apparent on
the surface of the glass. A pitted area affects the appearance of a glass container but
not the usability of the container. It is a minor defect.
d. Sagging Surface. This refers to a wavelike distortion on the surface of the
body wall. It is a minor defect.
e. Thin Spot. A thin spot is an area where the body wall is decidedly thinner
and weaker. It is a major defect. This defect refers to corrosion underneath the cap. It
is a major defect.
f. Check. A check is a checked crack. This defect is a slight, feathered crack
that does not leak; however, it weakens the body wall. It is a major defect.
g. Pitted Rust. This defect refers to corrosion underneath the cap. It is a major
h. Bead. A bead is a bubble in the body wall which exceeds 1/8 inch in
diameter. This defect weakens the body wall. It is a major defect.