> I suppose this is a pretty basic question: what should one use to bleach
> the color of a 100% rag paper, prior to coating with a sensitive emulsion
> and which will not interfere with the chemical process? For example, if I
> wanted to lighten a gray rag paper for brighter highlights prior to making
> a cyanotype?
One possibility to bleach a paper is to put it wet (or very humid) under
uv light. The light will create ozone which then will bleach the paper.
Klaus