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Packed, Stacked, Shipped: Know Your Corrugated Stacking Strength

How strong is your corrugated board? Standard ratings are a major guide to answer that question, such as stacking strength results from ECT (edge compression test) measurements. But several factors can cause compression and weakening of boxes packed and stored under load, such as storage time; relative humidity; pallet patterns (aligned columns, misaligned columns and interlocked); overhang; pallet deck-board gap; excessive handling and the headspace in the box. Even small variations in the creases in flaps and side panels, and packaging line labor practices, can multiply the effects of tiny flaws once boxes are packed, stacked and in the distribution chain.

One common culprit is the buckling of linerboard facings, which is visible on the outside of your boxes, and relative humidity (RH) is a major factor here. According to a presentation by Roman E. Popil, Ph.D. with the Georgia Institute of Technology, stacked boxes exposed to cyclical changes between 50% and 80% RH “last only about 1/5th as long as the same boxes exposed to a constant high humidity.” Another potential of stacking issues is using too low a grade of corrugated.

Leading suppliers are equipped to spot the signs and conditions of such problems, and offer solutions that range from handling advice to alternative designs and technologies such as facing and coating options, flute sizing and direction and suggestions for inner packing. With the right advice, we can help you arrive at the best, most cost-effective design whether a stock box or custom corrugated — with optimal stacking strength for your products.


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