Discoloration of printing papers

For some years I have noticed that prints made by 20th century
artists (e.g. Bracque, Clavi, Dubuffet, Jorn) exhibit a slight
discoloration or yellowing after having been exposed to light during
exhibition. Furthermore, I have noticed an enhanced discoloration
like a thin yellow/brown line along the edge of the
lignin-containing cardboard passi-partouts in which these prints
have been mounted.

In most cases this phenomenon has been noticed on "Arche Velin"
printing papers from France--they seem to be particularly vulnerable
to discoloration due to light. I wonder if the discoloration could
be the delayed result of chloral bleaching of the pulp? But what
really puzzles me is why the discoloration is enhanced along the
window edge of the passi partout. Does anyone have a plausible
explanation for that?

Another thing is how we are going to treat these prints? An obvious
choice would to bleach them, but that might damage the printing inks
and leave the paper all white. I have not tried to bleach any of the
prints since many of them are rare and expensive. Does anyone have
some experience in dealing with this problem? Simple wet treatment
on the suction table is not always enough to remove the
discolorations.

Michael Hxjlund Rasmussen
paperconservator, MSc
Vejle County Conservation Centre
H.O.Wildenskovsvej 22, Brejning
P.O.Box 55
7080 Bxrkop
Denmark
+45 76 62 11 56
Fax: +45 76 62 11 54


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                  Conservation DistList Instance 16:54
                 Distributed: Thursday, March 27, 2003
                       Message Id: cdl-16-54-018
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