Digital BW, The Print

Ernst Dinkla <e.dinkla@...> wrote:

> ...
> The use of protective coatings, Hahnemuhle, Premier, does wonders to 
> reduce paper white shifts of OBA papers ...

The OBAs are dyes, which seem to react more strongly to sprays.  The Claria dyes also have much better light (and gas?) fastness when a protective spray is used.  The black only Claria ends prints have a lightfastness that is close to UltraChrome (color) neutral patch performance.

> ... My view is that gas like oxygen-ozone is blocked by the 
> sprayed varnish.

At some point I'd like to test the Lascaux Fixativ spray (no UV blocker) and the Premier spray (with UV blocker) to see how the results compare.  Some years ago when Livick was doing a lot of testing, I believe a combination of Lascaux first (it soaks in better) and then a UV blocker appeared to extend print life the longest.




> 
> 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. ...

> 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 looked at some Aardenburg-Imaging <http://www.aardenburg-imaging.com/acceleratedagingtests.html> results and tried to compare the Epson Gloss Optimizer (R800/1800) results with the UltraChrome results on the same glossy papers (Premium Glossy and Luster).  I can't tell from the materials whether the Epson GO was turned on or off in those tests; I have assumed the GO is being used.  The Epson GO uses a lot (25 - 30%) of glycerol.  (See http://www.epson.com/cgi-bin/Store/support/supDetail.jsp?BV_UseBVCookie=yes&oid=30501&infoType=MSDS).  The R800/1800 overall has better fade numbers than the UC printers.  But that could have been due to no light pigments or the additional ones they use  (although the yellows are probably the same and it does better there too).  With respect to the paper white, in the tests where Premium Glossy is used, the UC printer had a very slight advantage.  With the Luster, the R800/1800 had the advantage.  (But there it was roll paper v. sheet, so there could have been a relevant variable there.)  At any rate, I'd say, assuming the GO was being used, there was not serious detriment to the inks from the GO and its high glycerol content.


 
> ... It is still a sound advice to avoid the high OBA content papers ...


Although it's interesting that natural papers also shift color -- bleaching whiter.  So, the best paper may have just enough OBAs in it so the effects balance each other.  Some H. Photo Rag tests suggest that is what Hahnemuhle succeeded in doing.

> and go for papers with good, normal whitening agents like Baryte 

Do the baryta papers have a polyethylene barrier in them?


> and TiO2.


Note the extent of bleaching of Arches watercolor papers and Epson Hot Press natural.  It seems like neither of these papers is bleached in processing as much as most of the others.  I experimented with bleaching Arches with H2O2.  It did bleach the paper somewhat, but peroxide is also a mild acid, so it affected the pH -- not recommended.

I also have tried a TiO2 wash with Arches.  That looks like it might be worth a bit more effort.  It's too early for any conclusions, but it did increase the whiteness.  Arches Hot Press has a bit of reflective sheen that makes the paper relatively brighter near where the light is reflecting off the paper.  With the TiO2, that sheen is reduce, with the effect that "off axis" brightness is increased noticeably.  Particularly where spotlights are use on it, this might significantly improve the brightness of the paper and the apparent dynamic range of the image.

Paul
www.PaulRoark.com