Digital BW, The Print

Looking for a bright white paper for quadtone printing, I've run 
across an issue already familiar to me from 30 years in 
traditional photography--optical brighteners and permanence. 
Posts on this list and elsewhere take the position that optical 
brighteners soon fade or, worse, turn the prints yellow. Is this 
really true?

Most darkroom papers incorporate optical brighteners. Baryta 
itself, which appears in virtually every fiber-based darkroom 
paper, is a brightener. Titanium dioxide is normally used as a 
brightener in  "RC" papers, some of which have tested for well 
over a hundred years of display life in various accelerated aging 
tests. Its brightening effect is reportedly long-lasting, not fugitive. 
(RC papers have had other permanence problems in the past, 
but these do not seem relevant to the whiteness issue in inkjet 
printing.) Wilhelm's tests of Epson Heavyweight Matte, which has 
brighteners in it,  apparently revealed no yellowing of the paper 
for at least 66 tyears of simulated display life. I would expect that 
any degradation due to brighteners would have definitely 
showed up in these tests.

I'm not a scientist, but I had to study the issue of brighteners as a 
serious darkroom worker. I came to the conclusion that 
brighteners were not automatically bad for longevity. It depends 
on the specific brightener used, its possible interaction with 
silver or other substances present in the paper, etc.

I'd love to hear from others about  the permanence of Legion 
Photo Matte, Torchon, and other papers that use optical 
brighteners. What brighteners are used? Is there any hard data 
that supports future yellowing? What kind of life expectancy do 
these papers actually have? Can't an inkjet paper be as white as 
a darkroom paper without the threat of major deterioration?

--David Stock