Investigation of the influence of a commercial glass protector on float glass surfaces by x-ray photoelectron spectroscopy

In this study, the influence of an established, commercially available glass protector for tableware has been investigated on the air side of soda–lime–silica glasses produced by the float process. The protective agent is a water-soluble phosphate glass with oxides of zinc, potassium and bismuth as its relevant components. By dissolving it in deionised water a saturated solution was prepared. Float glass samples were stored therein for up to 19 days and afterwards investigated by x-ray photoelectron spectroscopy (XPS). Furthermore, element depth profiles were analyzed. The investigations show that a precipitation layer of hydrated zinc phosphate of a thickness up to 13 nm starts to form on the float glass after long exposure while zinc diffusion into the glass takes place. Furthermore, tin specs on the air side act as a surfactant and fasten the formation of the precipitate layer. The study shows that precipitation and zinc diffusion are the main mechanisms behind the protective effect of the investigated glass protecting agent.