There is a lot of stuff to wade through on your web site... would you be kind enough to supply a more specific link that provides the data behind your assertion? (Not a challenge - just looking for info - thanks for the reply.)
See the attached graphs which show white point stability for both papers. That's some of the data behind my assertion, but these graphs probably call for a little explanation as well, so here goes:
Re: EEF - If we measure the CIELAB b* value (which tracks the blue-yellow component of the color ) then UV included versus UV excluded measurements can give us insight into the initial flourescence of the media and thus indirectly how much OBA is present. Exhibition fiber has a very high initial fluorescence factor with ∆b* = 6.7 for the UVinc-UVexc measurements (i.e, it's a very cool-white paper to begin with due to high OBA content). When that OBA totally burns out, we should expect to see the whitepoint stability graph leveling out at around 6.7 units of change in the ∆b value. But EEF keeps going higher as you can see in the plot which means it's yellowing more than we can explain merely by loss of fluorescence. Better papers will have lesser amounts or even no OBA, and will stay within 1 or 2 b* units of their initial value over the entire length of the test.
re: EPPL - the Epson Premium Luster paper has a different but still OBA related yellowing problem that's harder to track in accelerated light fade tests and thus has gone largely under reported in the published literature (including what I've published to date, sorry to say, but I'm working on fixing this accelerated testing issue). If you look at the whitepoint stability graph for EPPL, its ∆b* value is more erratic as the testing proceeded, but again shows very high amounts of yellowing at the end of the test which cannot be explained by mere loss of OBA fluorescence. Additional staining is occurring and it needs a dark storage or low intensity illumination condition added to the testing cycle in order to bring about the additional stain. The sample I have graphed here was allowed to stay in dark storage for several months after the 140Mlux hour exposure, and that amount of time was enough to induce the spike in the b* value you see at that point on the graph. Likewise, for the smaller bumps in the plot at the 50 and 90 Mlux hour marks. In those instances, the sample was not measured immediately after the exposure dose interval was completed. The dark storage time allowed more stain to grow in the sample, and subsequent high intensity illumination was able to bleach that stain back somewhat so the b* value went down again in successive measurements, hence the erratic nature of this plot. This is a complex phenomenon I have taken to calling the LILIS effect (stands for low intensity light induced staining), but suffice to say that it will definitely occur in a more steady manner with this product under real world display conditions over time because most display conditions are typically not intense enough to suppress the yellowing with light bleaching that counteracts this stain growth in higher intensity accelerated light fade tests. BTW, I'm now detecting this LILIS problem with essentially all of today's popular RC photo papers, not just Epson RC paper and not just RC inkjet media, either. That said, the Epson RC papers do tend to exhibit the problem more severely than other RC media, and that indicates there is much room for improvement of RC media if the manufacturers begin to pay attention to this problem. Anyway, it's part of my ongoing research. I don't have all the answers yet, but I'm working on ways to better characterize the problem so that printmakers who care about print longevity can make more informed choices.
lastly, if you want to check out the full reports for these samples, they are ID #s 210 and 225 in the AaI&A database. You need to log in to the AaI&A website to be able to download the full reports, but registration is free.
best,
Mark
http://www.aardenburg-imaging.com
