Ink as a barrier against paper discoloration

We are carrying out conservation treatments on XIX century cadastral
documents.  They were made in Trieste (Italy) in 1893 and bound
together shortly afterwards.  There are all sorts of papers, laid
and wove, lignin containing and lignin free, but generally speaking
wove papers are highly calendered and kaolin was found (FTIR
analysis).  Inks contain iron, as proved by XRF examination, but
they don't have a typical iron-gall behavior.  They are stable and
don't cause paper degradation.  Instead a rather puzzling phenomenon
occurs where a lignin containing paper is adjacent to a fairly good
quality wove paper.  The first induces severe discoloration on the
contact side of the latter, expect for inked areas: the manuscript
lines of the lignin containing paper seem to "protect" the adjacent
surface, where a "whiter" mirror image comes out.  On the same
surface this sort of protection is caused both by recto and verso
text lines of the lignin paper(!) whose discoloration doesn't seem
to be influenced by inks though.

An example can be seen at the following dropbox link:

    <URL:https://www.dropbox.com/sh/87ap3szq6dbervi/auJSHbHhQL>

Has anyone ever encountered this phenomenon? Could anyone explain
its chemistry or teach us a proper way to describe it in English?

Ketti Angeli
Conservation lab
Centro regionale di catalogazione e restauro
Villa Manin di Passariano, Italy


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                  Conservation DistList Instance 27:15
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