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It is important for the reader to understand the difference between "flatness" and "dimensional stability" characteristics. Particleboard and MDF are the recommended cores for high pressure decorative laminate and wood veneer work because of their excellent flatness. Fair dimensional stability (expansion/contraction in panel size) is acceptable unless the product is exposed to wide swings in relative humidity, generally below 25% or above 55% with swings of more than 30 points.

Characteristics of Core Performance 

Various characteristics above are influenced by the grade and thickness of the core and specific gravity of the core species. Visual Edge Quality is rated before treatment with edgebands or fillers and Visual Edge Quality of lumber core assumes the use of “clear edge” grade. Surface Uniformity has a direct relationship to the performance of veneers placed over the surface. Dimensional Stability is usually related to exposure to wide swings in relative humidity. Screw Holding and Bending Strength are influenced by proper design and engineering.

Due to adverse reaction of some veneers laminated to fire rated (FR), ultra low emitting formaldehyde (ULEF or NAUF), medium density fiberboard (mdf) causing discoloration of the wood veneer even months after installation, major core manufacturers have issued disclaimers in the use of FR cores. They strongly suggest that use of FR ULEF mdf and particleboard cores should be done after testing compatibility of adhesives, wood veneer and cores. Any resulting discoloration with the use of these cores may be exempt in their warranties. Use of FR ULEF cores should only be considered after consultation with the board supplier.

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