The Mullen Burst Test

The Burst (or Mullen) Test has long been considered an industry standard. It measures the force required to burst or rupture the face of a corrugated board. The Mullen Test suspends a piece of corrugated material and uses a machine to apply increasing levels of force to the face of the material until it bursts.

Burst Test results are given in pounds per square inch. A Mullen-tested box rated at 200# can withstand 200 pounds per square inch of force applied directly to the linerboard on the face of the carton.

Mullen Burst Test standards dictate a minimum board weight for the corrugated material. In other words, every square foot of the final corrugated material must contain at least the minimum amount of base paper material required by the standard for its Burst Test rating. For example, a single-wall corrugated cardboard box with a 275# Mullen Test rating must contain at least 175 pounds of base paper per 1,000 square feet of corrugated material.

The Mullen Burst Test is geared towards measuring the forces a carton may be subjected to during rough handling as well as the amount of weight the box can hold. It does not measure how much weight can be stacked on top of the carton. To understand stacking strength, you need to look at Edge Crush Test (ECT) ratings.

The Edge Crush Test (ECT)

The Edge Crush Test, or ECT, is a newer test developed to look specifically at how much force a corrugated material can withstand on its edges without crushing. Instead of applying force to the face of the corrugated material, as the Mullen Burst Test does, ECT applies force to the edge. Material is compressed top to bottom until it buckles.

Edge Crush Testing measures the force applied in pounds per linear inch of load-bearing edge and is reported as an ECT rating. 32 ECT is the most commonly used corrugated material.

ECT has grown in popularity since its invention in the 1990s because it provides a better measure of how well boxes will hold up to stacking and palletizing. Modern shipping and warehousing methods mean that most products are now shipped and stored in pallets, where boxes may be stacked several layers deep. So the box not only must be strong enough to hold the weight of the product within, but also have edges strong enough to hold all of the weight on top without crushing or deforming.

Unlike Mullen Test ratings, ECT ratings do not require a minimum amount of base paper in the corrugated material. This means that ECT-rated boxes are generally lighter and use less material than a Mullen-Tested box that is considered to be equivalent. This can help companies reduce shipping costs and improve environmental metrics.