Digital BW, The Print

I believe there are several factors that influence OBA burnout and media white point stability. Here are some of the key variables.

1) concentration of OBAs, ie.  how much does the initial media color depend on the incorporated OBAs. If very little, then total burnout produces only slight effect. If a lot, then total burnout produces large effect.

2). Location of OBAs. When located in top microporous coatings, the OBAs are extremely sensitive to oxidation (just like other dyes). The oxidation can be photochemically induced, but even more so due to ozone induced oxidation. The OBA's are more protected when located in subbing layers and paper core.  Many RC papers, for example, have subbing layers below the top ink receptor layer and above the PE/TiO2 layer where the manufacturer can include some OBAs.

3). Molecular structure of the OBA and interaction with the layer(s) in which they are embedded. For example, swellable polymers will indeed protect them more from oxidation, which in part explains why OBAs in traditional darkroom type photo papers have not gotten as bad a reputation (although some problems have been experienced in the field with traditional photo papers as well).

4) As a corrollary to item 3), the pore size of the micro/nano porous silcates used in the inkjet paper probably plays a role as it can also affect the oxygen penetration rates to the OBAs as well as the final physical shape of the OBA molecular chain structure due to electronic charge influences from the silicates distorting the bonds in the dye molecule.

5) Inclusion of additional tinting pigments in the paper size/coatings to achieve cooler media white point thus lessening the need for higher OBA concentrations.  Typically you will see lower L* values for papers that add some cool-white hue with tinting additives, and UV-cut spectral data should still show blue wavelength region effects due to the added colorant.

There's undoubtedly other variables as well, but these are some key variables that affect OBA fading impact on media white point stability.

cheers,
Mark
http://www.aardenburg-imaging.com

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla <edinkla@...> wrote:
>
> Op 12-1-2011 21:31, Paul schreef:
>    I'll have test samples of that along side samples
> > of the MIS EZ neutral ink I'm working on when it comes time for me to
> > stick them in the fader -- should be an interesting comparison.
> >
> > Paul www.PaulRoark.com
> 
> Paul, Mark if he is around,
> 
> For a week now I try to find some logic in what keeps the paper white of 
> some RC papers lasting while other RC papers fail on that in time. 
> Aardenburg pages. Low FBA content is a pro but not the only thing. It 
> looks like the dye ink compatible papers score nice on this and I wonder 
> if that is related to a swellable coating (gelatine, PVA) on top of the 
> RC base but a paper of the Ilford Classic category fails as well.
> 
> Any thoughts on that?
> 
> -- 
> Met vriendelijke groeten,   Ernst
> 
> Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/
> 
> |      Dinkla Grafische Techniek      |
> |         www.pigment-print.com        |
> |                 ( unvollendet )                 |
>