Transcript:

So, why is aluminum foil that you use at home, why is one side shiny and the other side not so shiny? Do you know why? 

Well, you understand how aluminum foil is made. It is made by sheet rolling of ingots of aluminum, which are poured from molten aluminum. And this rolling is done multiple times. For example, 4.5 meters by 1.5 meters by 0.5 meters, this block of aluminum can be rolled and re-rolled to make aluminum foil 12.5 kilometers long. 

So, during the rolling process, the thickness of these sheets is reduced to about less than 0.1 mils. One mil is a thousandth of an inch. So, it is one-tenth of a thousandth of an inch, the thickness. And to get the sheet to this thickness, you would need extremely small rollers. 

So, what they do is, for the final roll, they put two thick sheets together, and then they roll the assembly down. And the combined rolled sheet of aluminum is then separated, and the side that is separated is the matty surface (which is the dull side). And the side that is facing the rollers when they are being rolled is the shiny side. 

Now you know!