The essential glossary of corrugated packaging terms for quality control teams

Corrugated is an integral part of the packaging industry, known for its durability, versatility, and sustainability.

Whether you're a business owner, a packaging enthusiast, or simply someone looking to understand more about this ubiquitous material, getting familiar with the terminology is essential. This glossary aims to demystify the key terms associated with corrugated packaging, providing clear definitions to help you navigate this complex yet fascinating field.

NB. This glossary is an extract from our Escada Corrugating Process Troubleshooting Guide and is intended for use by quality control personnel, production supervisors, machine operators, and anyone involved in the manufacture of corrugated materials. It covers a wide range of defects, from common issues like warp and delamination to more specific problems such as washboarding and flute crush. Each entry includes a definition of the defect, a brief summary of its potential causes, and suggested remedies or preventive measures.

Whether you are troubleshooting a specific issue or seeking to enhance your understanding of the corrugating process, this glossary will serve as a valuable reference. By familiarising yourself with these terms and their implications, you can improve your ability to diagnose and correct defects, leading to better overall production outcomes.

Blistering: Formation of bubbles or blisters on the surface of the corrugated board.

Blowout / Fluff Out: When the adhesive fails to set properly, causing the layers to separate under pressure.

Board Crush: Compression damage to the board that reduces its strength.

Bonding Failure: Adhesive does not properly bond the liner and medium, leading to delamination.

Burnt Liner: Scorching or burning of the liner, typically due to excessive heat during the corrugating process.

Caliper Variation: Inconsistent thickness of the corrugated board, affecting performance and usability.

Corrugator Marks: Indentations or patterns left by the corrugator rolls, affecting the board's surface quality.

Cracking: Splits or breaks in the liner or medium, often due to over-drying or improper handling.

Creasing: The liner or medium develops folds or creases, compromising the board’s flatness and strength.

Delamination: Separation of the liner from the medium or the medium from the other liner.

ECT: Edge Crush Test. An industry recognised testing method for testing strength properties.

Edge Burst: The edges of the board burst or split, often due to handling or mechanical stress.

Edge Crush: Localized crushing of the flutes along the edges, reducing edge strength.

Edge Delamination: The edges of the board separate, often due to insufficient adhesive or pressure.

Feathering: The edges of the board are frayed or ragged, often due to dull cutting blades.

Flute Crush: Flutes are compressed, reducing the cushioning and structural properties of the board.

Flute Fracture: Breaking or cracking of the flutes, usually due to excessive pressure or poor paper quality.

Flute Lean: When the flutes are not perpendicular to the liner, causing structural weakness.

Flute Washboard: A repetitive pattern of waves along the flutes, often due to tension issues.

Gel Point: The temperature when the glue begins to gel and turns from liquid to solid.

Glue Line Defects: Issues with the consistency or placement of glue lines, affecting bond strength.

Green Bond: When the adhesive bond is still developing. Fibre tear is yet to be fully present.

Heat Damage: Damage to the board from excessive heat, resulting in brittleness or discoloration.

High-Low Flute: Inconsistent flute heights, resulting in uneven board caliper.

Liner Tearing: The liner tears during the process, often due to mechanical problems or paper quality issues.

Liner Impressions: Marks or patterns transferred from the corrugator rolls onto the liner.

Loose Flutes: Flutes are not tightly bonded to the liner, causing potential delamination and weak spots.

Misalignment: The liner and medium are not properly aligned, leading to uneven edges.

Over-Drying: Excessive drying of the board, making it brittle and prone to cracking.

Overheated Board: Board exposed to too much heat, causing it to become brittle and weak.

Pin Adhesion Test: An industry recognised testing method for measuring the adhesive bond strength.

Pinholes: Small holes in the liner or medium, often due to improper paper quality or mechanical issues.

Poor Edge Crush: Weak edges that cannot withstand compressive forces.

Pressure Marks: Indentations or marks caused by excessive pressure during production.

Score Crack: Cracking along the scored lines where the board is folded.

Side-to-Side Warp: The board is warped across the width, often due to uneven moisture or temperature.

Slinging: The term used for when the glue is being splashed or thrown from the glue roll.

Surface Contamination: Foreign substances on the board surface, affecting its appearance and performance.

Surface Pitting: Small pits / holes on the liner surface, affecting appearance and potentially structural integrity.

Surface Tear: Tearing of the liner surface, often due to mechanical stress or handling issues.

Tear-outs: Sections of the liner or medium are torn out, often due to mechanical issues.

Uneven Glue Application: Inconsistent glue coverage, leading to weak or unbonded areas.

Washboarding: A wave-like defect in the surface of the corrugated board.

Warp: Any deviation from a flat plane, including bowing, twisting, or cupping.

Wild Edges: Poor alignment of fluting & liners, causing a rough cut at the Slitter Scorer.

Wrinkles: The liner or medium develops folds or creases, compromising the board’s flatness and strength

Zippering: Flutes easily separate along the score lines, usually due to weak adhesive or improper curing.