items made from colorless, crystal, or colored glass for household and institutional use. Household glassware comprises drinking glasses, other types of glass kitchenware and tableware, and artistic and decorative pieces. The principal components of the glass are SiO2, Na2O, K2O, CaO, and MgO. Coloring agents used in the production of colored glass include CuO, MnO, Co2O3, CdS, Cr2O3, Se, and the oxides of such rare-earth elements as cerium, neodymium, and praseodymium. PbO is present in crystal, where it constitutes not less than 24 percent by weight. Household glassware is formed by pressing and blowing. For decorative finishing, the glass is polished or is etched by acids.