Originally posted by Kevin M
<br />As an added note, this wood was cut on the end grain, sanded to 12000mm, blo/ca (3)coats, assembled, inspected, put to bed.
Just a guess, but I would have to think the end grain cut has something to do with it.
It's hard to believe a pen sitting for 3 days would just have a crack in the finish.
The older wood should have been pretty stable ,but wood will react funny when subjected to different stresses.
If it was really dry the added oil from the BLO,heat from sanding,any number of possible conditions would add to conditions that caused the crack.
I am going to guess that the wood may have"checked" while turning.
Sanding filled in the grain.
The weak spot(especially since you said it goes all the way around the circumference of the pen) filled with the BLO and after sitting the effects or stress caused the finish to crack.
I would bet if you took it apart and turned off the finish you will find it is not just the CA that is cracked.
Sorry for the bad luck.