Parchment and sodium dithionite

Regarding parchment artifacts, have readers heard of--or
tried--using sodium dithionite to remove or lessen heavy iron
corrosion deposits? I have searched the literature without finding
reference to using sodium dithionite on proteinaceous materials. My
interest is an 18th century sheet that has a swath of heavy
corrosion near its center, about 1 x 6 inches, probably from the
metal can in which it was stored. Around the corroded area, the
sheet draws far out of plane. I would like to lessen the corrosion
so I can nudge the sheet to a flatter shape. I was thinking of
applying the s.d. solution either by dryish swabs or in a methyl
cellulose poultice.

Presumably it would also be advisable to remove and/or chelate the
corrosion to improve chemical stability?? I understand that topical
applications couldn't be as effective as the water baths possible
with paper objects, but would like to lessen the rust deposits as
much as safely possible. Any comments or suggestions would be
appreciated greatly.

Christine Smith
Conservation of Art on Paper, Inc.
2805 Mount Vernon Ave.
Alexandria, VA. 22301
USA
703-836-7757
Fax: 703-836-8878


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                  Conservation DistList Instance 18:8
                 Distributed: Wednesday, July 21, 2004
                        Message Id: cdl-18-8-034
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