When it comes to custom packaging for corrugated boxes, no matter what you are shipping, strength and durability should be a top priority. To say that every box is the same is a big mistake – but what is the difference, and how is strength tested?
Firstly, the strength of a corrugated box starts with the material used. A corrugated sheet has three main components, the inside and outside paper liner (the linerboard), and the interior, ‘fluted,’ portion (the medium). When a sheet of corrugated board is created, and the wavy interior (the medium) is attached to the liner with a starch-based adhesive, this works to resist bending and pressure and when placed vertically can sustain significant amounts of weight.
So how is that strength tested and how can you be sure it meets industry standards? The Edge Crush Test and the Mullen Test are the two industry-recognized methods that measure weight. When checking that a box meets industry standards, make sure that a Manufacturer’s Certification Stamp is visible. This stamp will also certify the type of test done, and the results (Mullen – most common is 200 lbs/sq. inch or Edge Crush – most common is ECT 32 lbs/inch).
There is some confusion regarding the difference between these two tests, so in an effort to clear up the confusion, here is a brief breakdown:
The Mullen Test – measures the bursting strength of corrugated board by testing how much pressure it takes for a box to rupture. To conform to the Mullen Test standard, a box needs to reach a certain number (200#, 275#), and the higher the number, the stronger the box.
The Edge Crush Test – measures the stacking strength of corrugated board by testing how much pressure a box can stand before being crushed. Like the Mullen Test, to conform to the Edge Crush Test, corrugated boxes need to reach a certain number (32ECT, 44ECT), and the higher the number, the stronger the box. The Edge Crush Test is best suited for stacking requirements because it provides lighter weight cartons with good stacking characteristics.
With Edge Crush you can change the weight of each of the papers but still maintain the same weight whereas with the Mullen Test the construction of the linerboard can’t be altered.
There are benefits to both of these tests, so discussing each one with your manufacturer is always a smart idea. That being said, it never hurts to be informed before that meeting!
For more about testing the strength of corrugated boxes please contact Packaging Technologies Inc. by calling 1-800-303-5883.