Bursting Test Explained

How the Mullen burst test works, what the numbers mean, when burst strength matters more than ECT, and how to specify board that survives rough handling.

The bursting test, also called the Mullen test, measures how much pressure it takes to rupture the wall of a corrugated box. A rubber diaphragm is inflated against a sample of board until the liner or flute fails. The result is given in kilopascals (kPa) or pounds per square inch (psi).

What burst strength tells you

Burst strength is a guide to puncture and tear resistance. It matters when boxes are sliding against each other in a lorry, pushed across concrete floors, hit by strapping or handled through multiple distribution points. It is less useful for predicting stack height.

How burst relates to board construction

Heavier liners and double wall construction both increase burst strength. A single wall box with 150gsm liners will burst at a higher pressure than the same flute with 125gsm liners. Adding a second flute layer, as in BC double wall, raises burst resistance significantly.

Burst versus ECT

ECT predicts vertical stacking performance. Burst predicts resistance to puncture and rupture. A box can have a high ECT but a lower burst, or vice versa. Choose ECT when the main risk is compression from pallets above. Choose burst when the main risk is rough handling, impacts or sharp contents.

When to specify for burst

• Export shipments with multi-handler journeys.
• Products with sharp edges or corners that press against the wall.
• Boxes dragged or slid across floors during picking and loading.
• Mixed pallet loads where boxes bear against each other in transit.

If your damages are splits, punctures or burst seams rather than crushed tops, burst strength is probably the property you need to improve. We can review a failed box and tell you whether the problem is burst, ECT or the box style itself.