Digital BW, The Print

On 02/29/2012 11:42 PM, Paul wrote:

> Test prints using very good inks from Jon Cone and HP had some bad
> Conservation Display Ratings in the Arrdenburg-Imaging
> (http://www.aardenburg-imaging.com) fade tests that had nothing to do
> with the pigments -- carbon sepia and Vivera. But the OBA burnout
> triggered the end point on the Conservation Display Rating even thought
> the pigments were not fading. That is, the images' overall appearance
> had changed noticeably -- not good. The poor papers that did this were
> Alise BW and HP Pro Satin. See http://www.aardenburg-imaging.com for the
> test reports.
>
> Paul
> www.PaulRoark.com

Paul,

there are possibly ten or more there that tested bad on paper white 
shifts while the inks did better.

The HP Pro Satin is an RC paper tested badly but for example Canon 
Heavyweight Satin, also an RC paper, tested far better at Aardenburg. 
The quality of the OBA must play a role and where they are located in 
the paper. For example in an RC paper in the paper base itself between 
the polyethylene barriers the gas fading of OBAs could be reduced.

Ten days ago I went through Aardenburg test results again to check paper 
white shifts and mentioned some observations on the Wide_Inkjet_Printers 
list. Here I repeat them:

The use of protective coatings, Hahnemuhle, Premier, does wonders to 
reduce paper white shifts of OBA papers next to the protection of the 
inks. Check some tests at Aardenburg where the same paper is used with 
and without. My view is that gas like oxygen-ozone is blocked by the 
sprayed varnish.

The printer applied gloss enhancers worry me a bit, it looks like the 
paper white shift
is increased with gloss enhancers, MIS glop the most. Fiber/Baryta
papers more than RC papers. Check two tests of Ilford Gold Fibre Silk 
with and without Glop. The test samples you mentioned should be seen in 
that light too. If Glop is in the inks too as an ink medium I wonder 
whether it influences MIS ink test results as well when applied on OBA 
papers that show paper white shifts more with Glop.

I have some guesses what could be the reason for the paper white shift
with gloss enhancer:
* the gloss enhancer itself changes color
* the gloss enhancer affects the OBAs. In literature I see glycol,
glycerol and PVA mentioned as additions to OBA dyes for different
reasons, one of them to increase the fluorescent effect. I wonder at
what cost. The three are normal ingredients in ink medium.
* the gloss enhancer changes the coating structure so gas fading of
the OBA dyes can happen faster.

I have to dig deeper in Aardenburg results, maybe something can be
deducted there. More tests to separate possible causes are needed.


BTW, the Canson Infinity Baryta Photographique that is in many ways a 
clone of the IGFS shows more paper white shift than IGFS. Could be a 
different surface that is more permeable or a different OBA used. I go 
for the first cause. It was noticed before that the surface looked 
slightly different.

Remains the fact that OBA content of whatever kind influences the color 
management and restricts the display conditions of prints if 
"metamerism" has to be avoided. For B&W too. It is still a sound advice 
to avoid the high OBA content papers and go for papers with good, normal 
whitening agents like Baryte and TiO2. Just enough OBA to neutralise or 
brighten the last type of papers a bit is then a wise compromise.

-- 
met vriendelijke groeten, Ernst
Shareware too:
330+ paper white spectral plots:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm