Discolored paper

A few months ago, we received an piece of art (acrylic on paper) in
our studio. The work on Fabriano paper was framed on plywood
(Meranti) and fixed recto at the edges with water soluble tape.
Underneath the tape, the paper had still a white tone, the remaining
unpainted edges of the paper had a light brown tone. Because of the
brown edges, we decided to bleach the work. First we cleaned the
object with gum powder, we removed the tape and further we treated
the edges recto with demiwater, we used the air brush and dabbed the
moist edges with blotting paper. Then we used hydrogen peroxide
(30%) in demiwater (10ml:90ml) and added a drop of ammonia (25%) The
pH of the solution was 7. We sprinkled this liquid recto two or
three times with the airbrush. Finally we  rinsed the edges again
recto with demiwater and dabbed them again with blotting paper. We
are used to this method and never had problems with it.

The treatment was really successful. The brown colour disappeared
and the paper kept a beautiful tone. But, after a few weeks,
meanwhile the object again hung on the wall, there were appeared a
million of little brown spots (like copper corrosion) in the edges.
It doesn't look like foxing, the spots are not as light as foxing,
but dark red brown. There are also yellowish stripes at some places.

Has any member had this problem before? Does anybody know how these
spots and stripes can occur? And how we can handle this problem?

Marieke Kraan
Bernadette van Beek
Restauratieatelier KOP
Arnhem
The Netherlands


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                  Conservation DistList Instance 17:16
                 Distributed: Wednesday, July 30, 2003
                       Message Id: cdl-17-16-003
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