My instructor informed me that iodine would work to remove emulsion on a print (or neg) acting as a good bleachng agent... I want to write or paint on the "agent" to spell a word on a finished print... One of my friends tried it on glossy fiber and nothing happened.. Left it on overnight, without washing.... Does the stuff work? What would work for this.. I assume, use it, leave until desired effect takes place then re-wash and dry?? I use FB papers.