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Everything You Need to Know About:

Shipping Boxes

By: Paul Gertin

Corrugated paper, often referred to simply as cardboard, permeates the world of professional packaging, shipping, and storage. Since their invention in the late 19th century, corrugated carboard boxes have almost entirely replaced wooden shipping crates as the primary means by which we package and transport goods. Despite being so commonplace, and seemingly simple to understand, corrugated shipping boxes can range quite widely in terms of size, strength, quality of material, damage-resistance, and more.

If you or your business rely on corrugated packaging to transport, store or market products, then there are a few things you need to know. With that said, let’s get to work unpacking the differences that exist between different kinds of corrugate.

Cardboard vs. Corrugate - What's the Difference?

The first thing you need to understand about corrugate is that it is different from cardboard. This is one of the most common misunderstandings when it comes to corrugated packaging. Cardboard is actually just a heavy-duty paper stock; made of multiple layers of paperboard, cardboard is best understood as being akin to a very thick paper. Cardboard is used in things like cereal boxes, shoeboxes, Kleenex, and other customer-facing packaging applications.

Corrugated packaging on the other hand, is a much stronger form of packaging which consists of two components: the medium and the liner. The liner is simply a flat material which is most often found on the outside of the packaging (in some heavy-duty boxes, there are multiple layers of liner). The medium is what sets corrugate apart from cardboard, and what gives corrugated packaging its strength. The medium sits between the liners and creates an arched shape which is referred to as a “flute.” When these two components are combined and converted into the structure of a box, they create what we refer to as corrugated packaging or shipping boxes.

corrugate cardboard shipping boxes

Strength and Durability

While all corrugated packaging consists of liners and mediums, the size and thickness of the flutes is a major determiner of corrugate strength. Flutes are available in five standard sizes: A, B, C, E, and F, with each corresponding to a thickness:

  • A Flute: the thickest profile, A flute corrugate is roughly 5mm thick and offers the most cushioning for products in transit, and extra strength for stacking.
  • B Flute:​ a popular choice for die-cut designs and self-supporting products, B flute corrugate is roughly 3.2mm thick.
  • C Flute: ​​​the most commonly used corrugate size today, C flute corrugate is about 4mm thick (slightly thicker than B flute).
  • E Flute:​ at 1.6mm thick, E flute corrugate is most often used in retail packaging for its thin profile and for its printability.
  • F Flute: the thinnest option, F flute corrugate is roughly 0.8mm thick and is used for many of the same applications as E flute.
  • flute size corrugate shipping boxes

    With a flute size in mind, you then should consider the type of board to use for your corrugated shipping box. Because board types are classified according to how many layers of liner and medium (or flute) make up the board, there could hypothetically exist an infinite number of board types (though a 100-wall board seems a bit unruly). With practicality in mind then, here are the most common board types used in corrugated packaging today:

    • Single-Face: this board type consists of one sheet of liner and one sheet of medium. This board type is often sold in roll-form, and typically used to wrap products in.

    • Single-Wall: this board type consists of one sheet of medium glued between two sheets of liner (see flute-size image) and is the most common type of board, used in everything from shipping to retail packaging.

    • Double-Wall: this board type consists of two sheets of medium glued between three sheets of liner and is used for more heavy-duty products.

    • Triple-Wall: ​consisting of three sheets of medium and four sheets of liner, this board type is the strongest, and is used for the heaviest of products.
    board size corrugate shipping boxes

    A final note on board type – not all flute sizes need to be the same size. A triple-wall board for example, can have an inner layer of A flute medium for extra cushioning, but a thinner medium on the outside for printing, or to save space.

    Closing Out

    Given the range of options that exist for corrugated packaging, it’s no surprise that this material has become the most widely used form of packaging in the world today. In addition to the range of options for corrugate strength and durability, the material is also environmentally friendly; 90% or more of corrugated material produced is recovered and used for recycling, making it the most recycled material in the United States year after year.

    Gertex’s packaging experts can help you find the ideal corrugated solution for your business needs. For a full overview of our corrugated products, click here.

    Contact us today for a free assessment by filling out the form here!

    paul gertin gertex solutions

    Paul Gertin
    President and Co-Founder