Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "John" <jrnolly@...> wrote:
>
> Mark:
> With dyes and swellable polymer papers, humidity conditions can vary the results significantly. When I was running my initial tests with Wilhelm using Ilford dyes 11 years ago, it became apparent that dye migration seems to happen at 50% and greater humidity conditions, which leads to premature magenta failure. (at least with the Ilford dyes we were testing) 


Hi John, yes I'm intimately familiar with the dye migration issue.  I'm the primary author of two key published papers related to the subject of humidity induced dye migration in inkjet media. Dye migration is not just an issue for swellable polymers.  It's an even more complex problem with microporous media as well, and specific mordanting additives tailored to a specific dye set are one way the OEMs can reduce it for their dye/paper combinations, but of course it not a perfect fix and besides, many people use "universally compatible" papers, so the problem persists with any dye-based printers.  You can find both of the papers I wrote on the WIR website at these respective links.

http://www.wilhelm-research.com/isj/WIR_JapanHardcopy2005MMG_HW.pdf

http://www.wilhelm-research.com/pdf/is_t/WIR_ISTpaper_2003_09_MMG_HW.pdf

Maybe not bed time reading, but these two papers cover a lot of interesting ground and will give folks an idea why the compounded issues of dye migration (which tend to cause loss of print sharpness, hue shifts, plus color saturation and density increases) versus light fading/gas fading (which usually go in the opposite direction with saturation and density losses) complicate getting a "clean" unconfounded test for fading characteristics of dye based inket systems.  Nonetheless, we do the best we can do to "settle" the short term migration before starting our fading tests. You can accelerate the migration which slows exponentially as it continues by pre treating at high humidity levels, but it's not a sure bet that the enlarged dot structure and ink mixing which then takes place is guaranteed to occur under more "average" end-user storage and display conditions. Bottom line:  this is another reason why pigments have so far won out in professional proofing and fine art applications where short term color and tonal drift cannot be tolerated to the extent that the average amateur will tolerate it in dye-based inkjet systems.

cheers,
Mark