The ingots of aluminium are heated to make them more malleable, rolled, passing backwards and forwards through large rollers as the slab gets thinner and thinner, and longer and longer. This metal strip is hot rolled to a thickness of 2 to 4 mm (2000 to 4000 microns) and then coiled, before being cold rolled to metal thicknesses of between 6 and 400 microns. The thinnest foil used for wrapping chocolates may be only 6 microns thick (about one-eighth the thickness of newspaper!), with household wrapping and cooking foil between 11 and 18 microns, lidding foil between about 30 and 40 microns, and foil for foil containers generally between 40 and 90 microns. he foil is then annealed by a thermal process to make it pliable: great care is taken to ensure the correct balance between flexibility and strength for different applications.

Alloys

The most common foil alloys - the 1000, 3000 and 8000 series - contain between 0.5% and 1.5% iron, 0.1% and 0.7% silicon and 0.02% to 1.5% manganese. Up to 0.2% copper may be added when additional strength is required.

Source: EAFA