Digital BW, The Print

Hello Richard,

>Something I've never understood is how Wilhelm has always managed to
give Ultrachrome prints on Epson Enhanced Matte and Watercolour
Radiant White better longevity than prints on Epson Velvet Fine Art -
which is totally against real-world experience. Enhanced Matte isn't
even acid-free and my understanding is that the same goes for
Watercolour Radiant White.
>Can anyone please cast some light on this?

Well, speaking of casting light <g>, my guess is that W's tests are
conducted by exposing prints to a strong calibrated light source until
some degree of fading occurs and then interpolating the time it takes
into the number of years it would take to get that amount of exposure
under normal conditions.  Ink fading in reaction to light has no
relation to the paper being acid free or not (I think, someone correct
me if this is wrong).  Depending on the amount of acid present, it can
take anywhere from weeks (newspaper) to years before brownish yellow
acid stains appear.  So W's tests only tell us how long the ink/paper
combination will resist fading, not whether the paper is archival in
other ways.

Four things are often mixed together when discussing an ink/paper
combination's archivalness: the paper's fiber content, acid content,
OBA content and the ink's fade resistance.  But these are different
and not necessarily related things and need to be evaluated
individually.  

For example, EEM is alpha-cellulose, contains acid, contains
(apparently) a very short lived OBA, yet has very good fade
resistance.  I've got an EEM Eboni BO print that's been getting direct
sunlight on my window sill for over 4 years.  It's dingy looking from
losing it's whiteness but the ink hasn't faded (it's beginning to show
a bit of color shifting), and has no acid stains (that could take
years to show up).  That's probably why it rates high in W's tests. 

I'm guessing that something in VFA's coating (perhaps the more
permanent OBA) which reacts with the ink is probably what makes it
less resistant to UV fading than with EEM. Actually, while EEM gets
slightly better ratings for color prints, if you go to page 3 of 9 at
this link 
      http://www.wilhelm-research.com/epson/R2400.html

...where the chart is for ABW prints, it shows VFA getting higher
ratings than EEM.

Anyway, there's just a huge amount that we don't know and nobody will
tell us.  

Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm