A chemical compositional heterogeneity develops on glass surfaces which have experienced rapid expansion/stretching, as in the press or press/blow process used in forming. A differential etching technique using HF & HBF4 is developed to demonstrate that such heterogeneities occur on the surface of commercial articles such as soda-lime silicate tumblers. Comparison with articles exposed to aggressive conditions in a dishwasher reveals that similar corrosion patterns appear in both cases, as alternatively corroded/non-corroded regions arranged as striations running vertically along the tumbler. Analysis of these striae by imaging ellipsometry indicates that they consist of ridges 50-150nm high in relief with a width & repeat distance of 0.05-0.15mm - in agreement with a physical modelling study & suggests that the ridges arise from durable low alkali glass.
