Investigating the mechanisms behind long-term board-restraint procedure enhancing the mounting's dimensional stability

The traditional mounting process involves a critical and time-consuming board-restraint procedure. It is widely acknowledged in practice that the dimensional stability of a mounting improves with a prolonged restraint period on the drying board. Yet, the underlying reasons for the enhanced dimensional stability from long-term board-restraint are not well-understood. This study investigates the mechanisms at play through systematic experimentation. It was found that humidity cycling enhances the dimensional stability of the mounting by diminishing its hydroexpansivity and irreversible shrinkage. Specifically, humidity cycling induces fiber hornification, which reduces the hydroexpansivity of the mounting. Concurrently, it facilitates the redistribution of stresses and strains within the board-restrained mounting, mitigating internal stresses and the resulting irreversible shrinkage. This study contributes to a deeper understanding of the board-restraint procedure and how it affects the dimensional stability of the mounting.