The end of the wood is dried first because the water ev […]
The end of the wood is dried first because the water evaporates faster. When the water at the end is lower than the fiber saturation point, the end cells begin to shrink. When the shrinkage stress reaches the strength limit of the wood, the end crack occurs. A longitudinal split occurs at the medulla or at the rough ray or along the outer panel. End-cracking along the medulla of the medullary board is almost inevitable because the medulla is the most concentrated area of ray-thin cells, and the transverse tensile strength is extremely low.
Hard lobes with thick wood ray are also prone to end cracking. For a few meters long edge board, the end crack is allowed within 10cm ~ 15cm, because part of the end is always cut off during processing. However, for edging boards or floor blanks, end cracking is generally not allowed.
The following measures can be taken to prevent end cracking: 1 If it is allowed, it is best to change the thick plate into thin plates or small squares for drying, which is most reasonable, and can effectively prevent end cracks and other drying defects. 2 The end crack will be cut off before the kiln is dry, because the original end crack is easy to extend. 3 Apply paraffin oil or thick paint on the end of the wood board where no end cracking occurs, which prevents the water from evaporating from the end. 4 When loading, the spacers at the ends of the stack are pressed as close as possible to the ends and aligned up and down. 5 When the kiln is installed, the ends of the pile and the pile are as close as possible to prevent the airflow from being short-circuited from the gap between the piles, so as to prevent the ends from wood drying chamber too fast. 6 For hard hardwood or thick plate which is prone to end cracking, try to use a soft drying process and pay attention to timely humidity control.