Edge Crush Test vs. Box Compression Test

Edge Crush Test vs. Box Compression Test (aka ECT vs. BCT): New Performance Metrics for Corrugated Square Off

by Rob Kaszubowski, CPP

Chainalytics

As packaging consultants we are constantly faced with the challenge of learning a client’s vernacular and acronyms – as well as common acronyms within the packaging industry. For years the standard for corrugated packaging has been the ECT or Edge Crush Test. Edge crush slowly surpassed Mullen burst as the standard metric for corrugated strength. (Read more about ECT vs. Mullen Burst Here).  The ECT value is then utilized to help calculate the “theoretical box compression strength” which is derived from the McKee formula which dates back to the 1960s.

Lately, the more common term around the industry is now the BCT value or Box Compression Test. This value is often tied to a company’s packaging specification as part of their performance spec requirements.  That means that depending on a number of factors (the weight of the box contents, stacking pattern, safety factor, length of storage, storage conditions, etc.) a company may call out a target compression value that their secondary packaging must meet as a minimum threshold for performance.

So for example, a very simple requirement in the past may have been:

§  Box style = RSC

§  Size = 15 x 12 x 10

§  Material = 44# C ECT Kraft

Now that same company may specify the BCT (Box Compression Test) value:

§  Box style = RSC

§  Size = 15 x 12 x 10

§  BCT = 940 lbs

At the end of the day the customer doesn’t care what makes up this box, or what the paper combinations are. They just want to be sure that it can hold 940 pounds and make it through their supply chain with their products unscathed.

To perform the ECT test, a 2” x 2” swatch of corrugated is cut from a sample sheet stock. It is placed in an edge crush tester machine and thus the ECT value is obtained.  

Common ECT target values include:

§  26 (B or C flute)

§  32 (B or C flute)

§  44 (B or C flute)

§  55 C flute

§  42 BC flute

§  48 BC flute

§  51 BC flute

§  61 BC flute

§  71 BC flute

Corrugated board consists of three combined layers of paper: a single face liner, medium, and double face liner. Just as there are multiple ways to slice up a pizza, there are also multiple combinations of paper that can equal a certain ECT value. The weight of the paper liners used typically depends on what paper weights the supplying paper mills typically carry and source to the corrugators.  The amount of recycled content or virgin fiber can also be a factor in the final ECT value.

Anatomy of Corrugated Board

So as companies look to standardize their packaging and consolidate sourcing they are looking towards a much more simplified corrugated box specification: one that no longer calls out the ECT value, but rather the BCT value. Packaging engineers and procurement teams are stating: I don’t care what you make the box out of, as long it meets my minimum strength thresholds. This shift in the market should ultimately make it easier for suppliers to focus on running paper combinations that they run well and run fast and deliver an optimized product.

If you have questions about what your minimum BCT values or stacking safety factors should be for your secondary or tertiary packaging, contact the packaging engineering team at Chainalytics.