Curling of SiC Paper - Buehler
This video from Buehler gives the answer for Silicon carbide paper curling. SiC paper has a tendency to curl when stored for longer period of times. All grit size papers are prone to curling. Hence it says that the curling does not affect the performance of the paper.
Run Time – 0:45sec
My SiC Papers Are Curling, What Should I Do?