Glass Failure Analysis of Tramp Glass

As a part of a product liability case, a glass failure expert was asked to determine if a piece of "tramp glass" found by a consumer (Upper left photo) was put into the bottle after it was opened. There was a companion bottle from the same six pack that also had glass contamination(upper right photo). If the tramp glass in the subject bottle was planted, then the glass in the "sister bottle" was also put in by the consumer. These were "twist off" bottles; therefore, it was decided that if the torque needed to remove the cap on the sister bottle was low, this would indicate the cap had been previously removed by the consumer. The removal torque was measured on the sister bottle, and it was twice that measured on control bottles. Thus, the cap on the sister bottle had not been removed, and the glass contamination entered this bottle during bottle manufacturing or bottle filling. From this it was concluded that the tramp glass in the subject bottle is also a manufacturing defect.

Botle Manufacturing Defect

Glass failure analysis expert performs a root cause failure analysis on a bottle failure. In this case a manufacturing defect was causing numerous failures on a manufacturing line. The tops of these small bottles were coming off. The upper left photomicrograph is with the two halves of the bottle re-assembled. The upper right photomicrograph is of one of the glass fracture surfaces. The failures were occuring just below the transfer ring at a glass molding defect. The molding defect is a fold in the glass that acts as a stress concentrator. The lower left photograph is of an unused bottle with the defect. This is an unacceptable manufacturing defect and the parts werre returned as non-conforming.