Machine dishwashing of glass in private households : Research results on glass damage

Abstract

Against the background of the introduction of the new, low-alkaline compact dishwashing detergents and the associated glass damage during automatic dishwashing a comparative test was carried out. Glasses of different origin and composition were subjected to a continuous dishwashing test with up to 1000 cycles which compared the highly alkaline conventional detergent with different new formulation variants of low-alkaline compact detergents obtained from the market as well as with water. While the conventional and carbonate-containing compact detergent did not cause visible corrosion, the detergent with a high disilicate content already caused serious glass damage after 50 washing cycles in the form of clouding and iridescence. These phenomena render the drinking glasses esthetically unsuitable. At the same time, on-glaze decoration of chinaware which is n o t resistant to machine dishwashing is protected by these last-mentioned detergents. Details of the processes in the washed glass surface were examined by means of XPS depth profiles u p to a depth of 300 nm . It could be shown that during washing with automatic dishwashing detergents of a high disilicate content silica from the wash liquor separates in a similar structure as the glass itself on the glass surface, which causes the corrosion phenomena clouding and iridescence. Active substances and constituents of the wash liquor can be incorporated in the deposited layer. Since the new, low-alkaline compact detergents are gaining more and more importance on the market, this paper was intended to clarify the causes of increasing glass corrosion during machine dishwashing.