[@Minimum]

Good to have you on board!

[quote=@Gisk]
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? 
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It is sort of brought up in more detail in Clariel since neither Sabriel nor Lirael really dabbled with any Free Magic beyond the bells.  There are degrees of it (or rather, the strength of the Charter Mark becomes weaker as the use of Free Magic increases) and it is suggested that it can be reversed but is difficult.

When one uses Free Magic they find it harder to connect to the Charter, long periods using Free Magic will further weaken this.  I believe this is a cut off stage where one simply cannot make it back to the Charter but in most cases it is possible, just difficult and prolonged.