My understanding is that OBAs have been used since the 1940's in photo papers. Obviously by now their effects should be fairly well understood. At least with inkjet prints were not dunking them in chemicals anymore.
Here's a press release by Hahnemuhle on OBAs in their products that I found interesting.
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Nice find. Been there several times this week to get real data on the Bamboo but didn't see this. What is interesting too is that alpha cellulose itself brings 95% white and cotton 90%, the OBAs can add 10-15 % but if you do not want OBA you better get alpha cellulose instead of cotton if it is about whiteness.
There's another thing not in this page that describes that the TiO2 whiteners can be used in much lower quantity than Baryte-Barite = Barium Sulphate needs for the same whitening. However TiO2 eats up too much UV light to let OBAs do their work. Barite doesn't show that effect so OBAs are more effective in combination with Barite.
I tried to find information whether the whiteness of TiO2 whiteners (there are more than one) is based on fluorescent behavior but couldn't find that. This UV thing is interesting as it also has an influence on where you will use OBA, in the paper base (like HM does in some papers) or in the coating.
The Hahnemühle advice at the end of the page to protect the more OBA containing paper behind glass must have been written with tongue in cheek as it will protect the OBA from falling apart due to less UV reaching it but the whitening effect is reduced as well by that.
Given some recent ozone testing results published in ColorFoto and Fine Art Printer one may wonder whether a good RC paper with an alpha cellulose base and TiO2 whitener in the polyethylene and no OBA would make a better exhibition paper for bare exposure than all the other qualities made right now. The surface preferably satin or semi-matte.
For example with the Vivera pigment and HP RC paper, two components of aging are estimated to be around 70 years: ozone fading of the pigments and the RC barrier falling apart. The lightfading resistance is 80 - 105 years. HM's PhotoRag however will show ozone fading of pigment between 50-60 years for the same ink in bare exposure, the lightfading resistance is more than 115 years. The RC + TiO2 barrier is much improved in technology since it was first introduced in analogue papers. It had a bad reputation but one may wonder if that is deserved over the last 20 years. Maybe it is bad taste to suggest plastic as a carrier of art, I know. Cotton, fiber, baryte and gelatine suggest quality for much longer.
There's no independent test of any of the fiber or fiber baryte papers published yet as far as I know.
Ernst Dinkla
Try: [a href=\"http://groups.yahoo.com/group/Wide_Inkjet_Printers/]http://groups.yahoo.com/group/Wide_Inkjet_Printers/[/url]