Iron gall ink and solubility

We have a question about phenomenon that has occurred on two 19th
century letters written in iron gall ink.  After humidification and
during the pre-wash of manuscripts for our iron gall ink treatment
protocol some areas of the iron gall ink turn blue. We discovered
this was due to a loss of blue ruled lines on one piece of
stationery.  It seems to have settled selectively right back to the
iron gall ink as a halo.  Most of the ink on the document stays the
characteristic brown without any change or sinking, but small
sections (possibly written with different recipes of the ink) change
across the page or along one sentence--here and there).

In one instance on the tail end of a 'd' changed to blue, on a third
letter. We are now doubling our attention on all solubility testing
of the ruled lines and will search the iron gall ink corrosion
website about what if any info there is about this selective
deposition and whether or not it can actually affect the long-term
stability.  Does anyone know of information or notice this in
similar 19th century manuscript collections? Also, would someone
know of any possible way to enhance the results of solubility tests
for these very faint blue lines?  Any indicator tests available?  We
don't want this to happen again yet it can be very difficult to
obtain a thorough test with simple spot tests. Thanks for any info.

And to look at this a different way--would research done on this
selective deposition (whatever is causing this to happen) point to a
different way to selectively treat the iron gall ink?

Ramona Duncan-Huse
Senior Director, Conservation
Indiana Historical Society
450 W. Ohio Street
Indianapolis IN 46202
317-234-0093


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                  Conservation DistList Instance 21:1
                 Distributed: Saturday, April 28, 2007
                        Message Id: cdl-21-1-022
                                  ***