A Brief Guide to Tests and Ratings for Corrugated Shipping Boxes

green check mark on stack of boxes
  It’s amazing to realize how much we rely on cardboard to protect the things we depend on. The food we eat, the consumer goods we use every day, even our treasured possessions when we’re moving—all packed in cardboard. AirSea Containers is a leading provider of the cardboard boxes that power shipping and commerce around the world, and we know how to make our boxes tough and durable. However, you’ll get more value and performance out of our corrugated shipping boxes if you’re using the right ones for you. Most corrugated cardboard boxes are rated using one of two tests: the Mullen Test (also called the Burst Test) or the Edge Crush Test. Although there are equivalencies built into the systems, you’ll usually find a cardboard box rated as one or the other. Why that is, and what it can tell you about the box’s performance specs, will be our topic for today.

The Mullen Test/Burst Test

First developed in 1887, the Mullen Test or Burst Test was the default standard for cardboard strength until the mid-20th century. In this test, a piece of cardboard is placed in a hydraulic clamp device called a Mullen tester. The operator uses the device to apply increasing amounts of pressure to the cardboard, noting at which point it bursts or ruptures. This number of pounds is reported as the Mullen Test rating. For example, a box made of cardboard that can withstand 200 pounds of pressure is rated as 200#. The Mullen Test is generally considered to be more accurate for boxes that are subject to individual rough handling, including being stacked and re-stacked and taken on and off of hand trucks individually. However, because most goods are now shipped on pallets, the industry developed another test: The Edge Crush Test.

The Edge Crush Test

The Edge Crush Test is a more recent invention that has become a new industry standard for cardboard box testing. An ECT measures the pressure that a piece of cardboard can withstand when placed upright on its edge, mimicking the pressure that boxes experience when stacked on pallets. This test is the standard for boxes that will spend the majority of their time in pallet shipping. Because pallet shipping is generally less rough on boxes than parcel shipping, boxes tested with an ECT can use less material to achieve the same loading capacities. Thus, if eco-friendly packaging is important to your mission, ECT-rated boxes can be a great option. cardboard boxes on a pallet

ECT-rated boxes are generally the preferred option for pallet goods.

Which Rating System Should I Go by When Selecting a Box?

Although ECT and Mullen-rated boxes are both widespread (and both available from AirSea), ECT is the most commonly used rating system today. However, it’s still worth considering which type of box might be best for your specific needs:
  • If your box will be shipped via pallet, stacked with many other boxes and rarely handled individually, the Edge Crush Test is likely to give you a more accurate picture of the box’s performance. It’s also seen as more accurate than the Mullen Test for double-walled cardboard.
  • If you expect your box to experience rough handling (such as a box that will be shipped to a consumer via a parcel service), a Mullen-rated box can offer a more secure choice. Although these boxes have been supplanted by ECT boxes in many industries, increased eCommerce parcel service shipping has some businesses taking a second look.
  • What if your box will experience both? This can be a complicated question, and the answer is likely related to what you’re shipping. Since ECT boxes are made with less material, they can save you a significant amount if you’re buying them in bulk as well as giving you a greener and more efficient packaging design. However, for very fragile goods that might experience rough handling (even if they’re stacked on a pallet most of the time), you may want the extra material that a Mullen-rated box provides. (For items like this, AirSea’s air pillow packs are another great option for cushioning your shipments.)
  • To cross-check the standards on a corrugated box, use one of the Mullen-to-ECT conversion charts available online.
woman with smartphone accepting delivery

Mullen boxes are often a better choice for boxes that will spend a long time in transit individually.

AirSea Containers offers a corrugated box for every need, and we have both Mullen-rated and ECT-rated models available. And for the ultimate custom corrugated solution, we offer custom cardboard shipping boxes (both hazmat and non-hazmat) at industry-leading prices and with great features like custom printing. Still got questions? Corrugated manufacturing is important to understand, but it can also be complex—so we’re here to help. Talk to the packaging experts at AirSea Containers by calling (866) 596-9448 or request a free quote today!

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