Roll 'em!

Let's start making a box by making corrugated board, on a long series of linked machines called a corrugating line.

The corrugating medium, which will become the wavy middle layer in the typical three-layer corrugated board "sandwich," is pre-heated and steamed so its temperature nearly reaches the boiling point of water, 212ºF. This softens the natural ingredients in the paperboard, making it easier to form into flutes.

The web, or long sheet of paper unwinding from the roll, is drawn between a pair of gear-like cylinders called corrugating rolls. This shapes the paper into a series of precise waves. Glue is applied to the tips of these flutes on one side — just the right amount, and at just the right places — and the flute tips are pressed against a flat liner.

This creates a singleface web, a continuous sheet of flat paper with fluted paper glued to it. To make single wall corrugated board, the exposed flutes of the singleface web have glue applied to them, and they're pressed against a second flat liner.

Other parts of the corrugating line press creases into the corrugated board at precise places, so later it will fold on these creases to create a three-dimensional box.

The continuous web of corrugated board is now so stiff that it can't be rolled up. Instead, it's cut into flat sheets, just the right size for making the boxes that have been ordered. The sheets are then stacked and set aside so the glue can dry properly.

How swiftly does all this happen? Modern corrugating lines can move at more than 1,000 feet per minute—more than 11 miles per hour, or three times as fast as a comfortable walk!