Parmigiano-Reggiano is made from unpasteurized cow's milk. The whole milk of the morning milking is mixed with the naturally skimmed milk (which is made by keeping milk in large shallow tanks to allow the cream to separate) of the previous evening's milking, resulting in a part skim mixture. This mixture is pumped into copper-lined vats, which heat evenly and contribute copper ions to the mix. It is named after the producing areas, the provinces of Parma, Reggio Emilia, the part of Bologna west of the Reno, and Modena (all in Emilia-Romagna); and the part of Mantua (Lombardy) south of the Po. Both "Parmigiano-Reggiano" and "Parmesan" are protected designations of origin (PDO) for cheeses produced in these provinces under Italian and European law. Parmigiano is the Italian adjective for Parma and Reggiano that for Reggio Emilia. Outside the EU, the name "Parmesan" can legally be used for similar cheeses, with only the full Italian name unambiguously referring to PDO Parmigiano-Reggiano.