Copperware, usually of sheet COPPER, hand-formed and soldered, was in common use for cooking vessels from the late 18th century. Most copperware of this period was imported from England or continental Europe, although so much has been imported in recent times by dealers that it is impossible to identify Canadian contexts. Canadian sheet-metal workers who produced copperware in the early part of the 19th century did not mark their work. Most existing Canadian copperware dates from the manufacturing period from 1880 to the 1930s. Cooking pots, measures and teakettles are found marked by McClary, GSW (General Steel Wares) and various other makers. Manufactured copperware was being produced in Canada as late as the middle 1930s. The metal was subject to tarnishing and contained corrosive salts that were toxic if mixed with food; therefore, use of copperware began to decline rapidly in the 1890s with the introduction of ALUMINUM cookware. By 1897 Sears Roebuck listed only copper teakettles and washtubs. As of 1901, the T. EATON COMPANY of Toronto no longer offered polished copperwares at all.