I Didn’t Know That...

Q: Why is aluminum foil shiny on one side and dull on the other?

A: Aluminum foil is manufactured by passing sheets of aluminum through pairs of steel rollers with progressively smaller spaces between them. Because aluminum is highly malleable, each step makes the sheet thinner, until it reaches a final thickness of about a thousandth of an inch. In the final step, however, two sheets are passed through back to back. The sides of the sheets that contact the steel rollers come out bright and shiny, but the sides that are in contact press into each other slightly, producing a finish that is rougher and duller.