Most of the cels I collect are from new shows 
(relatively speaking), and generally have been 
taken care of. . . Or at least haven't had enough 
time to suffer severely from abuse. I picked up 
an older cel I'm not sure what to do with. . .

It looks like it got wet and wasn't dried off - 
probably kept in damp conditions overall. The 
sketch was stuck (yellowed, with waterstains) and 
had started to mildew. . . ? It looks like a 
variety of the stuff on my shower curtain and 
looks like it's grown *into* the paint! o_O; It's 
on the back of the cel on the paint, and can be 
seen in greyish patches through the front as well.

I hope someone can advise me on how to treat the 
cel so that whatever this is doesn't spread. I've 
already destroyed the sketch to get it off the 
cel since there were parts of it harboring more 
of this stuff, but in places where it hadn't yet 
moved to the cel itself. To fully remove the 
sketch, I wiped off the severely stuck parts with 
a slightly damp cloth - only to find that one 
color of the paint (red) is semi-soluable in 
water. Enough to color the corner of the cloth I 
was using. So this also means the paint isn't 
something I'm used to either.

Below is a close up scan of the patches of stuff, 
both as they look on the cel (front) and how they 
look on the sketch. Anyone know what it is, how 
to stop it's progress - or even better - how to 
remove it?

Many Sharp Smiles,
--Drac