Discolored photographic prints

Leonie Gaertner <leonie_gaertner [at] arcor__de> writes

>Lately a large number of black and white photographic prints in our
>exhibition show a bright orange discoloration.
>
>The prints (on Agfa Multikontrast premium matt 321 PE paper) are
>laminated on kappa-board with a so far not identified commercial
>adhesive sheet.

Although orange isn't a color I'd associate with the problem,
"bronzing" or silvering due to exposure to peroxide or other
airborne chemicals is certainly a risk with most photographic papers
no matter how well processed they are. Fresh latex paint will also
cause it. The color of the bronzing may be unique to the paper you
have, but I think that's what it is. Agfa actually formulated a
neutral colored toner called Sistan to prevent it from happening.

We had great success with it in our lab after we made enlargements
that bronzed badly for a hair salon where peroxide was in abundance.
The new prints toned in Sistan showed no problems. We still have a
case of it, but since Agfa is out of business, I'd like to know the
formula. Agfa claimed in their testing that the image of resin
coated black and white paper toned with it would outlast fiber based
prints which were not toned.

The reason we don't see as much of this problem with fiber based
prints is that free silver ions in resin coated paper aren't able to
migrate into the paper base the way they would in a fiber paper.
They remain trapped on the surface where they can affect the image
sooner rather than later. Toning stabilizes these molecules in any
silver halide paper. Most toners change the image color to brown,
but Sistan is neutral. It's a shame to see it go along with the
photographic giant of over 130 years.

John Castronovo
Tech Photo and Imaging


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                  Conservation DistList Instance 20:31
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