What Mark just said about the fact that if you are using papers with brightening dyes incorporated into them, then you are essentially making dye hybrid prints is a good way of putting it.
And that is one of the critical differences between WIR rating system and AI. Aardenburg shows this distortion in a clear and linear way over time.
For Wilhelm to be giving these absurd stability figures for junk media like Epson (signature worthy) "Exhibition" Fiber, or HP Pro Satin rc, that are both full of low grade uv brighteners that will glow under black light if you test them, puts into question all of his tests in my opinion. It just becomes an inaccurate and distorted marketing tool for the paper manufactures that sponsor the data.
What he does do is include a tiny little footnote at the end of the test, where he describes the testing method, telling us to avoid papers with oba. But nobody reads that micro type, and even if they do they are at a loss to know just how those brighteners are effecting the outcome of the colorants in any objective way over time and with what inkset. In that way Wilhelm is just contributing to the ignorance about the media in question. It is a strange kind of scientific method.
In the case of the above mentioned papers, and many more commonly used papers, regardless of pigments used, all the high values of a print are are quickly being altered. You have three properties of color, which are HUE, INTENSITY, and VAUE. All three properties are being degraded by dye brighteners. Just like in the type C era, a whole generation of color photography will be degrading because of poorly made papers and lied to about their stability.
A gallery just asked me why I don't use the description "archival inkjet print" for exhibition. The answer is because it has no meaning, and neither do a lot of these WR accelerated tests.
john
However, if a light fade test's failure criteria are loosened further to allow more easily noticeable and quite possibly objectionable levels of fade (e.g. the WIR rating method) then any system non linearity can have greater and greater impact and create a potentially misleading outcome. In fact, such non linearity in system response can also come from the media properties not just the ink properties. If you think about it, when you print on media containing OBAs, you are using a dye-pigment hybrid system
cheers,
Mark
http://www.aardenburg-imaging.com[/quote]
