I'm scared about cels and tissue paper.  I have a 
cel that has tissue paper basically embedded in the 
paint such that I can't get it off even with water.  
Possibly as a result of being bonded to this paper, 
the cel has rippled.

The problem may be that this cel met the tissue 
while it was still fairly new, or it got too hot at 
some point in its life, but it still makes me not 
want to let my cels stick to _anything_.

On the other hand, the mylar bags are indeed very 
nice-looking.  I've been experimenting with using 
them on a few cels to see whether the "static 
electricity" stickiness will actually be a problem 
in the long run.  I put a piece of paper 
temporarily behind the cel to slide it safely in 
and out of the bag.

For most cels I use 2 mil polypropylene bags of a 
size that fits exactly in a standard Itoya 11x14 
celbook (good to prevent sliding).  I have no 
evidence on their preservation abilities vs mylar 
and they are not nearly as crisp and clear, but 
they look decently unobtrusive and are cheap enough 
to wantonly cut up and slip between cel layers.

--Atiya