What Is Corrugated Cardboard and How It's Made

Corrugated cardboard is one of the most common and versatile materials used for packaging and shipping. At its core, corrugated cardboard is a composite of three or more layers of paper: two flat outer layers called linerboards and a rippled, wave-like inner layer called the flute. That flute gives corrugated its characteristic strength, shock absorption, and ability to resist bending while staying very lightweight.

For a beginner-friendly mental image, imagine a corrugated sheet as a sandwich where the filling is shaped like small arches. Those arches distribute pressure and create a cushion for whatever is inside the box. This simple structure is what makes corrugated cardboard ideal for protecting goods during handling and transit.

Here is a simplified outline of how corrugated cardboard is made in a modern plant

• Pulping and papermaking: Raw materials (usually recycled paper and some virgin fibers) are pulped and formed into large rolls of linerboard and corrugating medium. These rolls are dried and wound into reels.
• Corrugating: The corrugating medium passes through a set of heated corrugating rolls that shape it into the flute profile. Different roll sets create different flute sizes (e.g., A, B, C, E, F), which affect thickness and cushioning.
• Adhesive application: A starch-based adhesive is applied to the peaks of the fluted medium. The fluted layer is then pressed between two flat linerboards so the adhesive bonds the layers together. This forms single-face (one liner + flute) or single-wall (liner-flute-liner) board.
• Lamination for multiwall boards: If stronger board is needed, additional corrugated or liner layers are glued to create double-wall or triple-wall board.
• Cutting and converting: The wide corrugated sheet is cut, printed if required, and converted into box blanks using die-cutting, scoring, and creasing. These blanks are folded and glued or taped to form boxes.

Different flute types give different properties

• A-flute: Thick, good cushioning and stacking strength; often used for fragile items.
• B-flute: Thinner, higher crush resistance; common in die-cut packaging and retail-ready boxes.
• C-flute: A balance between A and B; a common choice for shipping boxes.
• E and F flutes: Very thin; used for retail packaging and smaller boxes where printing detail and smooth surfaces matter.

Practical advantages of corrugated cardboard

• Lightweight: Keeps shipping costs down while still protecting goods.
• Protective: Flutes absorb shock, resist crushing, and cushion items against impact.
• Customizable: Easily cut, die-cut, printed, and formed into many box styles and sizes.
• Cost-effective: Widely available and typically affordable, especially when made from recycled fibers.
• Recyclable: Most corrugated is recyclable and commonly collected by curbside programs

Common applications include e-commerce shipping boxes, consumer goods packaging, point-of-sale displays, and protective inserts. For example, electronics manufacturers often use double-wall corrugated boxes for flat-screen TVs to combine stacking strength with impact protection; a beverage distributor may use single-wall C-flute boxes for cases of bottles.

Limitations and considerations

• Moisture sensitivity: Corrugated cardboard degrades when wet. For humid or wet environments, consider water-resistant coatings or waxed variants (though waxed boxes can be harder to recycle).
• Weight limits: While corrugated is strong relative to its weight, there are practical limits—very heavy items may need reinforced or multiwall board.
• Compression over time: Long-term stacking can compress flutes and reduce protection; proper palletization and pallet overhang control are important.

Beginner tips for using corrugated cardboard effectively

1. Match the flute type and board strength to the product: choose thicker flutes for fragile items and thinner flutes for retail display boxes where printability matters.
2. Right-size boxes to reduce movement inside: add inserts or void fill if needed to prevent shifting.
3. Consider moisture protection if items will face humidity or rain during transit.
4. Label with handling instructions and consider printing brand and return information to improve customer experience.

In short, corrugated cardboard is a deceptively simple material that delivers a powerful combination of cushioning, strength, and cost-efficiency. Whether youre a small business shipping products or a consumer curious about how your package protects whats inside, understanding the basic structure and manufacturing process can help you make smarter packing decisions.