Local clouding of glass after machine dishwashing

Abstract

The local clouding of glasses after dishwashing near the mouth rims on a coffee pot made from borosilicate glass, on a wine cup made from lead crystal glass and near the stem base on a wine cup made from barium Silicate glass has been found to be due to damage during manufacture. The examined clouding is different from the two well known types of filming and etching cloudiness related to the reactions of glass with water and detergent in the dishwasher. The intensive study on the wine cup of lead crystal glass shows that a phase Separation was induced during the flame treatment on the sharp rim and base. The aggregates of Pb-rich spheres scaled off when the thin covering of SiO2 rich skin was eroded away and consequently holes were formed on the glass surface on the micrometre scale, which resulted in light scattering and the clouding of the glassware. Evaporation species from warmer regions onto the colder areas of the glass surface could be observed, but they are not the reason for the local clouding in this study. Dendritic thin corrosion products caused by air exposure could be detected on the undisturbed glass surface as well.