Mullen vs. Burst, What’s the Difference?
Burst Test (Mullen) vs. Edge Crush Test (ECT)
When talking about how strong and durable corrugated boxes are, there are two main tests that are used: the Burst or Mullen Test and the Edge Crust Test (or ECT). Both of these tests help us understand how much pressure or force the cardboard can handle, but they do it in different ways. We’re here to simplify things.
Burst (Mullen) Test
The Burst Test checks how well the surface of the cardboard can hold up under pressure. Think of it like pushing your finger against the surface of a balloon to see how much pressure it can take before it pops.
Why it’s important: It tells us how much impact the surface of the cardboard can withstand from both internal and external force. This test focuses on the quality and strength of the liner board (the walls of the box) and depends on the fibers.
Why it’s used: It works great for irregular handling. If shipping something through UPS or Fedex, for example, a package can experience multiple points of mis-handling. In this scenario, Burst Strength is a good option.
Edge Crush Test (ECT)
The Edge Crush Test (ECT) checks how well the edges of the cardboard can hold up under pressure. Think of this pressure like stacking a bunch of books on top of the cardboard to see if it can hold them without collapsing.
Why its important: It tells us how much downward pressure, or weight, that a box can handle before collapsing. This test is important for knowing if the cardboard can hold up when boxes are stacked on top of each other and focuses more on the flutes.
Why it’s used: It works great for stacking in a warehouse or trailer (when properly secured and loaded).
Key Differences
1. What They Measure:
Mullen Burst Test: Looks at how strong the surface of the cardboard is.
Burst Strength Test (ECT): Looks at how strong the edges of the cardboard are.
2. When to Use Them:
Mullen Burst Test: Useful if the cardboard needs to resist punctures or pressure on its surface.
Burst Strength Test (ECT): Useful if the cardboard needs to handle being stacked or having weight on top.
3. Results:
Mullen Burst Test: Gives results in pounds per square inch (psi) – how much pressure will burst the surface.
Burst Strength Test (ECT): Gives results in pounds per inch (lb/in) – how much force it takes to crush the edges.
Why is this important to understand?
It is important to understand the application prior to determining which test is right for you. We would like to note that as you are getting pricing for boxes, it is key to ensure your quotes compare apples to apples. The Mullen test relies on a better quality linerboard and is often times more expensive. Additionally, it will feel sturdier. So when quotes come back, make sure the quote is for the right test. You might be saving money, but you might not be getting the same box. We’ve seen it over and over again— customers who are buying boxes from Uline for example, get approached by another distributor or packaging company. In an effort to save them money, the new company quotes a 32 ECT box. Uline primarily uses burst strength, and thus a 200lb test. Due to the heavier weight liner board, this box will generally be more expensive. The 32ECT and 200lb burst should be equivelant in strength. But because they are focused on a different type of strength, the boxes will feel different in quality. On the flipside, you might be using a burst strength box, when the type of strength you really need is ECT. Hence, you are spending more than you need.
Conclusion
Both tests are important for making sure the cardboard is strong and reliable. The Mullen/Burst Test helps us know if the surface of the cardboard can handle pressure, while the Edge Crush Test helps us know if the edges can handle being stacked. Knowing these differences will help you choose the right type of cardboard for the different types of jobs.