What is ECT? The edge crush test measures the compressive strength of the corrugated board itself, expressed as force per unit of length. It is the number most often used to specify a board grade, and it is a property of the combined board rather than of the finished carton.
What is BCT? The box compression test measures the assembled, filled carton under a descending load until it fails. It reflects what actually matters in a warehouse, but it depends on box size, perimeter, board caliper and how the box is closed, not only on board grade.
How are the two related? BCT is estimated from ECT using a standard formula that also takes box perimeter and board thickness into account, so two cartons made from identical board can produce quite different results. Asking for strong board without giving dimensions and stack height does not produce a usable specification.
Why does specification matter over time? A carton that passes on day one can fail after months in a humid warehouse, because corrugated loses strength as it absorbs moisture and as load is sustained. Safety factors applied in practice commonly fall somewhere between two and five, depending on humidity, stacking duration and handling.
What else weakens a stack? Overfilling, uneven pallet patterns, cartons overhanging the pallet edge and misaligned columns all reduce real stack performance far more than board grade does. Loading practice is covered in the container loading guide, and pallet patterns in the palletizing and stretch wrap note.
How should you specify to a supplier? Give the stack height, the storage duration, the climate, the product weight, and whether the pallet is stretch-wrapped or strapped. That lets a supplier propose a board grade and flute combination rather than guessing. Flute and structure basics sit in the corrugated box basics guide.
When is testing worth doing? When changing board grade, moving to a heavier product, extending storage time, or shipping into a humid climate. Testing a filled carton under load costs little compared with a failed shipment. Procedures are outlined in the transit tests note.
Chengtop produces corrugated shipping boxes and protective inserts at our Wuhan plant. Send product weight, stack height and destination through the quote request page and we will come back with a quote.
