Not all boxes are created equal—and choosing the right one can make a big difference. Whether your product is heavy, fragile, or oddly shaped, the strength of your packaging matters. Corrugated boxes are made of layers of paper with fluted (wavy) material in between, which helps them stay strong and protect what’s inside. But how strong is strong enough? That’s where two key tests—Mullen and ECT—come in. In this newsletter, we’ll break down what these tests mean and how to choose the best material for your product.

Mullen vs. ECT: What’s the Difference?

When selecting corrugated materials, understanding the difference between the Mullen Burst Test and Edge Crush Test (ECT) ratings is essential.

Mullen (Burst Test):
Measures how much pressure the material can withstand before bursting. Best for products with sharp or protruding features that could puncture the box, such as wine bottles or fragile items.
ECT (Edge Crush Test):
Measures the stacking strength of a carton. Ideal for products that are heavy but not sharp, where the biggest risk is the box collapsing under weight. Think bulk shipments or palletized loads.

When to Upgrade or Downgrade

Your Material

Packaging failures can often reveal when it’s time to adjust your material strength:

Crushed cartons? ➜ Upgrade to a stronger ECT.
Holes or punctures? ➜ Switch to Mullen-rated material.
Perfect condition but high cost or poor automation performance? ➜ Consider downgrading to a more economical or machine-friendly board.

The right packaging should protect the product, run smoothly on your equipment, and fit your budget.

Optimizing for Print Quality

Print clarity matters—especially if your packaging doubles as branding.

Flute size affects print surface.
Larger flutes (like C-flute) create deeper valleys, leading to visible gaps or ink inconsistencies during printing.
Smaller flutes (like E-flute) offer a flatter surface and sharper print quality.
In double-wall applications, B-flute is used on the outside to enhance the print surface while maintaining structural integrity.