What Is Corrugated Cardboard (Feedstock)? Simple Beginner Explanation

At its core, corrugated cardboard feedstock is a composite paper product made of flat linerboards glued to a fluted (corrugated) medium. This structure gives corrugated boards their signature strength-to-weight ratio and cushioning, making them ideal for shipping and protecting goods. This beginner-friendly explanation covers composition, types, manufacturing basics, properties, common uses, and how to choose the right feedstock.

Basic composition

• Linerboard: The flat outer layers that provide surface strength and printability. These can be kraft (strong, brown) or recycled/testliner (often grayish).
• Corrugating medium (flute): The wavy layer between liners that provides resilience and vertical compression strength.
• Adhesive: A starch-based glue bonds linerboard to the corrugated medium during corrugation.

Flute types and what they mean

Flute size affects cushioning, stacking strength, and printability. Common flute profiles include:

• A flute: Thick, good cushioning and stacking strength, used for heavy or fragile items.
• B flute: Thinner, better for die-cutting and printing, common in retail packaging.
• C flute: A versatile middle-ground for many shipping cartons.
• E and F flutes: Fine flutes used for high-quality printing and compact retail boxes.

Grades and terminology

• Single-wall: One flute layer between two liners—common for lightweight shipments.
• Double-wall: Two flutes, offering higher stacking strength for heavier loads.
• Triple-wall: Three flutes, used for very heavy or industrial shipping situations.
• Virgin vs. recycled content: Virgin fibers (kraft) offer higher strength and brighter print, while recycled content is cost-effective and more sustainable.
• Test metrics: Edge Crush Test (ECT) and Mullen Burst Test gauge stacking and puncture resistance respectively—useful when specifying feedstock.

How corrugated feedstock is made (high-level)

Paper mills produce linerboard and corrugating medium from pulp (virgin or recycled). Corrugators heat and shape the medium into flutes using corrugating rolls, apply adhesive, and combine liners to form single- or multi-wall board. The finished feedstock can be supplied as sheets or reels to converters who cut and fold into finished boxes.

Common uses

• Shipping cartons and e-commerce mailers
• Protective inner structures and inserts
• Retail packaging and point-of-sale displays
• Pallet trays and outer packaging for industrial goods
• Reusable and collapsible packaging solutions

Performance considerations

When selecting feedstock, beginners should think about:

• Stacking strength: Will boxes be stacked? Use a higher ECT or double-wall construction for heavy loads.
• Shock and vibration: Choose flute types and inserts for cushioning delicate items.
• Printability: For branding, finer flutes and better liners improve print quality.
• Moisture resistance: Standard corrugated is susceptible to moisture; consider coatings or special liners for humid environments.
• Sustainability: Recycled content, FSC certification, and recyclability are key considerations for eco-conscious brands.

Simple selection checklist for beginners

1. Define product weight and fragility.
2. Decide on print/branding needs.
3. Estimate handling and stacking loads during transit and storage.
4. Choose single- or multi-wall construction accordingly.
5. Request ECT/burst data and a prototype to validate choice.

Final note



Corrugated cardboard feedstock is a versatile, recyclable, and cost-effective packaging material. For beginners, learning the basics of composition, flute types, and performance metrics will make it much easier to choose the right material for your product and logistics needs.