Cracking

/ˈkrækɪŋ/

General Definition

Cracking refers to a phenomenon where the surface or coating of a printed material, such as paper, board, or packaging, experiences fracture, tearing, or splitting along the Fold line or where pressure is applied. This defect is particularly common in materials with short fibers, thick boards, or those featuring rigid surface coatings like heavy UV varnishes or thick laminates. Cracking not only ruins the product's visual appearance but also seriously compromises the quality and durability of the packaging structure.

Real-World Usage

One primary cause of Cracking is the failure to properly prepare the material before the Fold. When a Die Line is designated for folding, the appropriate process must be chosen. On thick materials, if superficial pressure is used instead of Creasing (which creates a deep groove), the board fibers cannot bend during the Fold and break, resulting in Cracking. This fracture also indicates that the Scoring process (which makes a minute, precise cut), was either not performed correctly and along the board's grain direction, or its pressure was improperly set for the material thickness. Cracking is a manufacturing defect directly linked to the wrong choice between Creasing or Scoring methods.

In the packaging industry, preventing Cracking is a vital principle. For thick boards, using Creasing with a die and crease roller, displaces the fibers and creates a safe bed for the Fold. Conversely, even in light materials where the Die Line is not a full cut, precise Scoring aligned with the grain is essential to prevent fracture on sensitive edges. These measures ensure the final product remains durable against repeated opening and closing.

Consultant's Note

As a technical consultant, to minimize the risk of Cracking, the material type and its coating must first be thoroughly analyzed. It is important to note that materials in drier environments are prone to more Cracking; therefore, controlling the humidity in storage and production halls is crucial. The main technical solution is performing rigorous tests before mass production. The depth of the Creasing or the pressure of the Scoring must be calibrated along the Die Line to ensure the material is perfectly prepared for the Fold. Additionally, ensuring that the Creasing or Scoring process is executed along the material's grain direction prevents Cracking caused by the natural resistance of the fibers.

Another strategy involves applying post-press methods like matte or gloss lamination, which although they can cause coating Cracking themselves, actually strengthen the material structure if properly scored or creased. Disregarding the grain direction, improper calibration of the Scoring or Creasing tool on the Die Line, and low humidity are the main causes of Cracking that must be continuously monitored on the production floor to maintain final quality.

Packdemy Council Insight

Kevin Pinto

Strategic Advisor

Cracking occurs when the surface of the board or its fibres break or whiten along the fold during bending. This is especially visible on dark colours, metallic inks, and recycled boards where surface strength is lower. Cracking indicates that the fibres have been stressed beyond their limit, often due to poor creasing, incorrect board grain, or excessive ink density around fold areas. This not only affects visual quality but also weakens the carton, resulting in poor shelf appeal and reduced functional performance.

To prevent cracking, operators must select the correct matrix width, creasing pressure, and rule combination for the board thickness. Running bend-tests before production ensures that the board folds cleanly without surface damage. Designers should avoid placing heavy solids or varnishes over fold areas, and printers should consider primers or aqueous coatings to strengthen the surface. Poor creasing or excessive scoring pressure is a common cause—once fibres are crushed too deeply, cracking becomes unavoidable. Consistent monitoring during production helps maintain clean, professional folds.

Aligned with: Bobst / TAPPI / Packaging World