A weird story a friend told me--

He had framed some very valuable cels (Warner& Disney)in 
picture frames and had them hanging on his walls for 
years.  One day there was that lovely Northridge,CA quake 
you may remember.  All his pictures fell and the glass
broke. The broken glass had sliced ALL the framed cels to 
ribbons, as neatly as if he had taken a razor blade to 
them.  He lost several thousand dollars of cels this way.

Now he uses plexiglass in his cel frames, maybe that's not
a bad idea..?