Architects have known for thousands of years that an arch with the proper curve is the best way to span a given space. The inventors of corrugated fiberboard applied this same standard to paper when they put arches in the corrugated medium. These arches are known as flutes and when anchored to the linerboard with a starch-based adhesive, they withstand bending and pressure from all sides.
When a section of combined board is placed on its end, the arches form rigid columns, capable of sustaining a great deal of weight. When force is applied to the side of the board, the space in between the flutes acts as a pillow to guard the container’s contents. The flutes also serve as an insulator, providing some merchandise protection from sudden temperature fluctuations. At the same time, the vertical linerboard offers more strength and shelters the flutes from damage.
Flutes come in various standard shapes or flute profiles (A, B, C, E, F, etc.). A-flute was the first to be developed and is the largest common flute profile. B-flute was developed next and is much smaller. C-flute followed and is between A and B in size. E-flute is smaller than B and F-flute is smaller yet.
In addition to these five most common profiles, new flute profiles-both larger and smaller than those listed here-are being created for more specialized boards. Generally, larger flute profiles deliver greater vertical compression strength and cushioning. Smaller flute profiles provide enhanced structural and graphics capabilities for primary (retail) packaging.
Different flute profiles can be joined in one piece of combined board. For example, in a triple wall board, one layer of medium might be A-flute while the other two layers may be C-flute. Combining flute profiles using this method allows designers to control the compression strength, cushioning strength, and total thickness of the combined board