Iris prints

Just a few additional comments to Andrew Robb's discussion of Iris
images from DistList Instance 12:57. (Note that my comments are in
regard to ink jet images in general and not necessarily specifically
Iris images.)

Humidity has definitely been a problem when testing ink jet images
for dark a light stability. We found that many samples when
preconditioned to 80% RH prior to testing resulted in transfer of
dyes (particularly magenta) as well as bleeding. At the last ANSI
meeting in December, it was decided that tests for dye migration
were important. It is a problem for accelerated aging because it
could cause density to increase or decrease depending on what
physical phenomena was occurring (even if the dyes weren't fading.)

The dark stability of ink jet dyes generally seems to be quite good,
but the light stability can be a problem. One of the biggest
difficulties is that the light stability is so substrate dependent
(and this is a real headache for anyone providing data on ink jet
images including the manufacturers.) Work done by Dr. Scott Williams
last year suggested that the dyes might be quite sensitive to
polymers in the substrates and that certain polymers possibly
promoted photo-reduction via electron transfers down the polymer
chains.

For up-to-date information from Henry Wilhelm, check out his web
site at <URL:http://www.wilhelm-research.com/> This is his new web
site, although it's still under construction. (He is trying to add
an FAQ.) He has promised to keep the PDF format page with his light
fading test results up to date. Note that Henry tests at 60% RH.

Henry raised the problem of catalytic fading between dyes at ANSI
and this will probably influence the test targets used by testing
labs. In his example, a yellow and magenta dye performed relatively
well by themselves but when they were combined to make red, one of
the dyes performed well while the other faded very rapidly.

I might add that waterfastness tests were also discussed and it was
surprising to learn that one of the manufacturers had found that
dipping and swishing a print in water was sometimes less destructive
than exposing the image to rain or a dribble of running water.

Douglas Nishimura
Image Permanence Institute

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                  Conservation DistList Instance 12:59
                Distributed: Wednesday, January 20, 1999
                       Message Id: cdl-12-59-001
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