I gotta confess, I'm a comic book collector. 
(Gosh, I bet you can't imaging how I went from 
comics to cels, huh?!? ;) ) This means I know all 
about mylars and acid free backing boards and the 
line.  Is cel archiving the same?  Should I be on 
the outlook for "acid-free" paper backing in my 
portfolios?  (I live in Boston, so there are lots 
of art stores to buy from, just so long as I know 
what to look for!) Is it okay to put a backing 
board behind a cel?  It seems like the paint will 
stick to almost anything (besides, for some goofy 
reason, non-matching backgrounds.  Go figure!) 
and I'm so new to this, I'm a little jumpy! :)