Quote Originally Posted by RedSun View Post
The blue top layer of Fuji paper is not part of the Dye. It is washed away in pre-wash. It appears to be protective coating, and indicator of the emulsion side of the paper.
I worked on Ektacolor paper for 5 years (in the '70s) and it was made like PE says. I can't imagine any reason for a 'protective coating' or an 'indicator of the emulsion side of the paper'; especially in a layer that washed away.

There might be some specialized material for aero use (or something) that behaves as you describe.