Digital BW, The Print

Hello Doug,

>I believe I recall the primary problem with optical brighteners in 
>paper being that they have a tendency to lose their whiteness over 
>time. Am I remembering correctly?

Maybe, but maybe brightness instead, or maybe both.  Some papers are
whiter than others before OBAs are added, so a given degree of burn
off may have different effects.

 
>I'm assuming this shows up as "yellowing", but wondering if Paul or 
>someone else has quantified just how much of a change we are talking 
>about, and approximately how quickly it can be expected to happen in 
>an  otherwise stable paper/ink combo. (And does the "OBA effect" 
>happen pretty consistently across similar papers, e.g. "brights", 
>"naturals"  w/OBA's, etc.?)
 
>Finally--just eyeballing it, are we talking a bright paper that ends 
>up looking more like a natural, or is it something more extreme? 

My own opinion is that it's less extreme.  I have some papers that
have been hanging here unprotected under fluorescent and window light
for two years that don't look any different than a fresh piece (PR and
Merlin Smooth).  But we don't know what kind of time frame we're
talking about, is 2 yrs enough?.  The only sign of burnoff I've seen
so far is with Condor BW which is very bright and very white.  After a
few months exposure it is slightly less bright, but not less white,
and then seems to stabilize.  It's barely noticeable.  Hawk Mtn papers
says their paper base is very white before the OBAs are added.  

>What I'm getting at here is of course, would a purchaser be struck 
>by the change in say a Hahnemuhle Photo Rag over the years, or 
>would you really have to compare a fresh print to an older one to 
>even notice?
> 
>So many questions! 

And good questions they are with answers not easy to find.  There are
also different kinds of OBAs, and newer ones are supposedly better
than older ones.  Lots of variables.  Paul has some good points.  If
you have any doubts it might be better to just avoid them, but then
you severely limit your choice of "look".  There is some further
discussion of this, including a reply from Diana York of Hawk Mtn
Papers, at the bottom of the "Great Paper Chase" article #5 at the web
link below.

Regards,
Clayton


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