More Defects

 (2)Defects due to poor handling and seasoning

There are different defects due to poor handling and seasoning depending on whether the log have been converted or not.

(a) Defects in timber which has not been converted
Shakes are defects in logs, which have not been converted, or in large timbers. There are a number of different 'shakes': star, frost, heart, ring and cup shakes. Shakes are serious splits between annual rings or along medullary rays. Tension forces build up in the tree while it is growing because different parts of the tree are growing at slightly different rates especially if the tree grows on the slope of a mountain. If the trunk is not seasoned properly, i.e. it is dried out too fast, then parts of the timber will split or separate and will appear as star, heart, ring or cup shakes. Also if the free is carelessly felled where it is allowed to fall, perhaps over a rock or a fallen free, these shakes can occur. Frost shakes occur when logs are poorly stacked and left out in freezing weather, resulting in the timber splitting along the grain.




(b) Defects in converted timber due to poor seasoning


Twisting: the boards warp and twist longitudinally (along the length of the board).


Cupping: cupping is warping across the width of the board.



 Bowing: is sagging along the length of the board.



 Spring: the board remains flat but curves along it's length.





Case-hardening: the board is dried too fast leaving the outer layer of the board dry but the inner core still wet.






Honeycombing: if a case-hardened board is not seasoned properly the inner core will spilt like a honeycomb.





Collapse: the cells of timber are flattened due to excessive shrinkage.






 Materials Wood
 Rot & Preservation