What Are Glass Container Bottom Defects?

By: Berlin Packaging Specialist

Several defects can occur during the manufacturing process of glass containers. Here are some common examples of glass bottom defects, such as baffle mark, spike, shear mark, and sunken or deformed punt.

Chain Marks defect consists of marks on the bottom of the bottle caused by contact with the conveyor belt immediately after manufacture.

Chain Marks

Crizzled Bottom defect is small axial grooves grouped around the baffle line.

Crizzled Bottom

Deformed Bottom defect occurs when the center of the bottom is lower than the external rim of the bottom.

Instability of the container.

Deformed Bottom

Cracked Bottom defect consists of web-shaped cracks.

Cracked Bottom

Inclined Bottom defect occurs when the bottom is not completely perpendicular to the axis of the bottle. It may be inclined to one side or wavy.

Instability of the container.

Inclined Bottom

Flash at the Seam Between the Blow Mold and Bottom Plate defect is a projection of glass > 0.5 mm that runs around the seam between the finishing mold and bottom plate, due to incorrect join between the mold and the bottom plate leading to protruding glass.

Poor resistance to knocks and thermal shocks.

Flash at the Seam Between the Blow Mold & Bottom Plate

Spike defect is a projection of glass extending upwards from the bottom on the inside of the jar or bottle. More frequent in press-blow process, and in containers with a broad mouth.


Sunken or Deformed Punt defect is a slough or deformation of glass in the punt, which may make the bottle below capacity.


Sunken or Deformed Punt

Baffle Mark defect is an imprint on the bottom due to poor fit between the baffle plate and the blank mold.

The stability of the container, its resistance to heat treatments, and the internal pressure resistance may be compromised.

Baffle Mark

Shear Mark defect is a mark on the surface of the bottle caused by the shears.

Aesthetic problem.

Shear Mark

Shifted Bottom Plate defect occurs when the body of the container has shifted at one side by ≥ 1 mm. The bottom axis is not aligned with the body axis.

Risk of scratching, not over 0.5 mm for decorated items.

Shifted Bottom Plate

Experiencing defects in your glass containers? Talk to Berlin Packaging Quality Specialists today!