Although returnable glass bottles offer significant advantages over other beverage containers in terms of reduced consumption of energy and natural resources, they also pose some problems for the brewing industry and beer trade. In particular, after repeated use the outer surface of the bottle tends to become scuffed, which spoils its appearance and can reduce its attractiveness to the consumer. Since 1981, Asahi Breweries, the second largest brewing company in Japan, has introduced a number of different coatings for application to scuffed bottles in order to restore their appearance. The development of the different coatings is described. The currently used coating, introduced in 1989, is based on a polyorgano siloxane resin, with a volatile polydimethyl siloxane solvent which penetrates and fills even very narrow or deep scratches before evaporating and leaving the solid coating behind. Two types of coating machine are used, both of which are fully automatic and operate in conjunction with the bottle labeller. The coating is washed off with caustic when the bottle is returned after use. Although it is only about 10 microns thick, it contributes significantly to the bottle's resistance to both internal pressure and external impact. No problems are known to have resulted either from chemical reactions involving the coating during bottle washing or from contact between the coating and the beer.
Keywords : coating damage glass bottle maintenance