What is the difference between mullen and ECT testing?

Corrugated cardboard boxes are so common, it can be easy to take them for granted. We tend to think about what we put in them, while barely giving the box itself a second thought. They are ordinary indeed. But they are so, so much more than ordinary. (Credit: corrugated.org)

As a material used for packaging, corrugated paper has been around since 1871, used in it’s single-face configuration for protecting glass and kerosene lamp chimneys.  It took over 2-decades before it was used to form a box (circa. 1894).

The most common corrugated boxes are single wall boxes comprised of 3 paper layers: 2 outer liners and the medium.  These three elements combined make up the strength of the box.  All corrugated materials are required to adhere to one of two corrugated testing standards: the old Mullen Burst Strength and the new Edge Crush Test (ECT).

What is the difference between Mullen and ECT?

Mullen Burst Strength is the original corrugated testing standard.  This test measures the amount of force, pounds per square inch, required to ‘burst’ through the side of the box. 

The Mullen test (bursting) was thought to correlate poorly with another important factor, stacking strength. In the 1990’s, the Edge Crush Test (ECT) was added to Item 222 and Rule 41 as an alternative to Burst Strength (Mullen) and Basis Weight. 

Edge Crust Test was developed in 1991 and measures the top to bottom compression strength and how much force the material can take before it buckles. 

Keep in mind, these are tests used to determine performance under a set of conditions.  All tests are done on the material used to convert a box.  What you put in the box, the shape, weight, fragility, duration, shipping conditions – they’re all important.

Is one better than the other, or are they equivalents?

No and no.  Because these two tests measure two different aspects of corrugated, you cannot assume that one is better than the other nor that they are equivalents.  However, there are strength ratings in each considered as alternatives.  For example, 32# (ECT) is viewed as an alternative to 200# (Mullen). 

Single Wall Alternatives:

Double Wall Alternatives:

Example: a regulation bowling ball is 8 ½” in diameter, weighing up to 16 pounds.  If I put a bowling ball in a 32#C RSC box that is 8 5/8” X 8 5/8” X 8 5/8” and drop it 10-times (ISTA 3A), it won’t likely survive the test, intact, without any damage.  The same is true for the Mullen alternative, 200#C materials.  However, if I were to add a layer of cushioning protection to evenly distribute the weight (1.7# PE Foam), increasing the box dimensions by 1” in every direction, both box materials would likely perform well.

In addition to the weight distribution; the size of the box, void-fill materials (bubble, paper, air pillows, etc.) used, and the corrugated strength will have an impact on the right material choice.  This starts to bridge into the big picture of ensuring your product arrives as expected at its destination.  If you need any help determining the right combination, please do not hesitate to contact us!