The root cause of "crazing"—a network or linear pattern of fine cracks—on the surface of melamine-faced boards (decorative panels), emphasizing a mismatch in thermal expansion/contraction rates (coefficient of thermal expansion) between the decorative paper and the substrate.

. What is True "Crazing"?
Definition: Fine, web-like or linear cracks appearing on the surface of decorative panels.
Characteristics: The cracks are irregular and crisscross, resembling shattered tempered glass.
Distinction: This is a structural failure, distinct from superficial scratches or damage.
. Root Cause of Crazing: Mismatched Coefficients of Thermal Expansion
The fundamental physical mechanism is that the coefficient of thermal expansion of melamine decorative paper is higher than that of the underlying panel substrate.

During Hot-Pressing:
Under high temperature and pressure, both the panel and the decorative paper expand outward from the center.
During Cooling:
After hot-pressing, both materials contract inward from the edges toward the center.
Because the decorative paper contracts more than the substrate, it exerts strong tensile stress on the panel underneath.
This sustained, uneven stress eventually causes deformation and cracking—known as "crazing."
. Key Factor Influencing Crazing Risk: Ash Content of the Base Paper
The document clearly identifies the ash content (or filler content, primarily calcium carbonate) in the base paper as the critical factor determining the paper’s expansion coefficient and thus its susceptibility to crazing.

High Ash Content → High Crazing Risk
Example: Warm white paper.
Reason: Warm white paper contains a high level of calcium carbonate (chalk/filler). This inorganic filler lacks flexibility, making the paper brittle and reducing its tensile strength, so it cracks easily under contraction stress.
Conclusion: “The higher the ash content, the greater the risk of crazing.”
Low Ash Content → Low Crazing Risk
Examples:
Wood-grain printed paper: Very low ash content.
Pure wood pulp paper: Made from 100% virgin wood pulp, virtually no ash/filler.
Reason: Wood pulp fibers form an interwoven, natural mesh structure with high tensile strength and flexibility, enabling them to better withstand contraction stresses without cracking.
Conclusion: Wood-grain papers have a “significantly lower” risk of crazing.
. Regional Differences
More Common in Northern Regions: The issue is noted to occur more frequently in northern areas.
Reason: Northern climates experience severe cold and large temperature fluctuations in winter. The pronounced contraction at low temperatures intensifies the stress caused by the mismatched expansion coefficients, making crazing more likely.