Digital BW, The Print

Op 3-1-2011 5:02, Paul schreef:
> "John"<jrnolly@...>  wrote:
>>
>> ... most indoor display situations have minimal UV exposure.
>>
>> Of a much greater concern is oxidation due to pollutants in the
>> air. Ink jet prints need to be sealed, ...
>
>
> I've always suspected that was why the Lascaux, which apparently
> soaks into the coating better, added to the fade test results
> relative to the UV spray by itself.
>
> I've looked for true oxygen barriers, and there appear to be none
> that are suitable for our us.  Oxygen gets through all of the
> transparent barriers we have, including acrylic.  But slowing it down
> does seem to help.  It's odd that even slowing the air movement
> around the pigments or dyes seems to help slow the oxidation.  I've
> wondered if air movement is analogous to blowing on a the embers of a
> fire.
>
>
> A fade test result of mine relating to coatings that I found
> interesting was that in a high humidity test a matte paper that was
> coated with the polyurethane faded faster than one that was not
> coated.  I speculate that the water vapor got in through the back and
> stopped the pigments from being dried out by the lamp.  Whether this
> would happen in normal display is debatable.  Accelerated testing is
> often said to exaggerate the longevity of the images because the
> brighter than normal light dries the pigments, and water/humidity
> acts as a catalyst for the fading/oxidation.  But, unless the print
> is encapsulated from both the front and back (perhaps by barrier
> paper), coatings that are just on one side of the imaging substance
> might actually have a negative effect.
>
> Paul www.PaulRoark.com

Paul, interesting find on the polyurethane.

Xenon lamp testing with increased intensity to get faster fading results
will have that effect of drying out the samples, the darker the patch
the hotter it gets. I guess that increasing humidity in the test chamber
doesn't work in the actual top layers of patches like that and will
shift the relation of fade results between different patch densities.

I thought PVA and gelatine can be oxygen barriers. What I recall of
fruit drink cartons is a PVA layer somewhere in the wall's sandwich of
aluminium, polyethylene, paper to do right that. The other layers there
to keep water in and for strength.

I still believe that modern RC papers should be independently tested on
the total of their aging effects, the RC papers reputation is based on a
bad history and they should get a second chance in my opinion. I wrote
that when the Fiber/Baryta papers were introduced and I still think so.
The RC papers show better gas fading resistance (based on some older
German tests of inkjet papers). FBA's if contained in the paper base
between the Polyethylene barriers live longer for the same reason and
there are now some new qualities like the Ilford Galerie Smooth Pearl II
RC that have that high load/buffer of FBA in the paper base and most
likely little in the coating. The main question is the aging of the
barriers and their bond with the paper base and paper coating. Right now
estimations are 75 years life for barrier life. Then there is the
outgassing effect when RC papers are framed behind glass. For unframed
display and with the print coated afterwards RC papers could have a lot
of advantages, especially for dye inks + compatible RC paper versions.
The good results with Claria and Vivera dye/paper systems show that already.


-- 
Met vriendelijke groeten,   Ernst

Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/

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