A California Glass failure analysis expert witness was asked to examine a failed wine bottle. A portion of the bottle top broke off midway down the cork as the cork was being removed. The root cause failure analysis revealed that the bottle had received a impact to the side. The distinct Wallner lines (see the photomicrograph above) located near the origin demonstrate that the impact was severe. The interaction of the crack front with the vibrations generated by the impact caused very visible Wallner lines. There was no manufacturing defect associated with this failure. When and how the impact occured cannot be determined from this failure analysis.