Cardboard Definition

Cardboard is a heavy wood-based type of paper, notable for its stiffness and durability. It was first invented in China some time in the 15th century, and is used for a wide variety of purposes. One of its more common uses is as a packaging material.

Prefabricated Containers

The American Robert Gair invented the corrugated cardboard box in 1890, consisting of pre-cut flat pieces manufactured in bulk that folded into boxes. Gair's invention, as with so many other great innovations, came about as a result of an accident: he was a Brooklyn printer and paper-bag maker during the 1870s, and while he was printing an order of seed bags a metal ruler normally used to crease bags shifted in position and cut the bag. Gair discovered that by cutting and creasing cardboard in one operation he could make prefabricated cartons. Extending this to corrugated cardboard was a straightforward development when the material became available. By the start of the 20th century, corrugated cardboard boxes began replacing the custom-made wooden crates and boxes previously used for trade.

The corrugated case was initially used for packaging glass and pottery containers, which are easily broken in transit. Later, the case enabled fruit and produce to be brought from the farm to the retailer without bruising, improving the return to the producers and opening up hitherto unaffordable export markets. (There had previously been a great deal of waste when, for example, oranges were craned out of the hold of a ship, having been bulk loaded into it.)

Will Keith Kellogg first used cardboard cartons to hold flaked corn cereal, and later when he began marketing it to the general public, a heat-sealed waxed bag of Waxtite w as wrapped around the outside of the box and printed with their brand name. This marked the origin of the cereal box, though in modern times the sealed bag is plastic and is kept inside the box rather than outside.

Corrugated packaging has undergone a minor resurgence in recent times due to the trend towards environmentalism. It is now common for cardboard to be manufactured with a partial content of recycled fibers.

Today's corrugated cardboard

Today's corrugated board usually consists of outer flat sheets (liners) of puncture resistant paper, sandwiching a central "filling" of corrugated short fiber paper (fluted paper, or "medium"), which resists crushing under compression and gives cushioning protection to the box's contents.

The "liner" and "medium" (outer and inner portion of the final corrugated cardboard product) are glued together along the outsides of the peaks and valleys of each flute, normally using starch adhesives. The starch is derived from corn, wheat or potato. Thus the complete make-up of corrugated board is from natural, sustainable materials in plentiful supply and the board is fully recyclable and can be pulped  down to make more paper for more board once it has ended its own life.

The board has high end-to-end strength along the corrugated flutes, so the box is normally designed with the flutes running vertically for stacking strength. The modern method of testing the stackability of a corrugated box is called the Edge Crush Test (ECT), but until recently boxes were measured with a "bursting strength" test.

Paper made from hardwood, short fiber pulp, has good compression strength and is easily mouldable with moisture and heat, but is weak in tension and tears easily. Paper made from softwoods,  with their longer fibers, on the other hand, is strong in tension and resists puncturing and tearing better and is less plastic, so tends to keep its shape. It also provides a better surface for printing.