Quote Originally Posted by DarkroomDan View Post
I have never seen or heard of this stuff so I don't really know anything more than what you and the product website say but it maybe that this stuff, not unlike many alt-photo processes, is UV sensitive.
See:
http://www.pburch.net/dyeing/howtodyewithlight.shtml
http://www.pburch.net/dyeing/vatdyes.shtml