So when one dabbles in free magic, their charter mark is corrupted. I have two questions that might have been answered in Clariel(or I may have just missed) if anyone has any insight. 

How quickly is the mark corrupted? Is it a binary state(it either is or isn't) or are there degrees? Is it instantaneous? We know the Abhorsen's blood lets them dabble without corruption. 

Secondly, is it possible for your mark to be purified?