What is a Flute?

Published On: April 20, 2022Categories: Industry News

Corrugated board has proven to be one of the most reliable and versatile products, from retail packaging to the boxes that we carry out from grocery stores. While they differ in size and purpose, these boxes share a structure that ensures their durability: a flute.

Inspired by the Rome Arch–one of the strongest engineered structures– a flute is an inverted and reverted roman arch between the liners of a corrugated board.

How is a flute made?
With enough heat and moisture, a flat paper can be pressure-rolled into those arches. Then, two additional layers can be added: an outside and an inside layer that can all be glued together with cornstarch to support the flute.

The fluted paper is made from different materials than the outside liners. The fibres of a flute must be able to withstand steam and cornstarch. Most fibres of a corrugated box can be recycled many, many times, and often there is only a week between pick-up of the old recycled boxes and the paper machine!

Types of flutes
Flutes can be made to support any job a customer requires, from shipping needs, high printability, to storage efficiency. Some can be made vertical (arches visible from a birds eye view) to withhold the weight of being stacked.

In North America, the most common flute types are the B flute and C flute. Letters are assigned to flutes depending on their size–ranging from an A flute with tall and wide arches to an E flute with short and tight arches. An E flute is used for products that require a high print quality, like promotional material. If the arches are too far apart, the board will sag and the print will not turn out clearly.

On average in Canada, corrugators are producing B flutes at about 250 meters per minute; at this rate, it would only take 2 minutes and 13 seconds to produce a length of corrugate that’s the height of the CN Tower or 14.5 seconds to produce a length of corrugate that could wrap the boards of the Leaf’s Scotiabank Arena!

Veronica Del Rei