Analysis of the glass fragments by X-ray microanalysis, and comparison of the results with data from the jar from which the fragment was reported, enable analysts to determine whether or not the glass fragment came from the same batch as the jar, and hence whether a breakage on a filling line is likely to be the cause of the problem. Experience from analysis of complaint samples suggests that the numbers of such incidents are much less than they used to be, indicating that good operating practices are having their effect.