Removing silking

We are currently working on a large manuscript map from 1794.   It
was previously repaired by the Public Records Office in London
around 1938, and their treatment included adhering silk gauze across
the bottom quarter of the map.  This area is very brittle with many
cracks and losses, and the silking has split along the tears in the
map and has contributed to further losses as the map is rolled and
unrolled.

The media is not water sensitive.  Small spot tests suggested that
the silking should easily be removed with water, but we have only
had about 97-99% success because eventually we run into areas where
clusters of fibres delaminate off the map surface and cling to the
silk fibres. These problem areas are concentrated in the most
discoloured areas of the map which also appear to be abraded under
the silk.  I'm starting to wonder whether some kind of consolidation
is required before the silk is removed.

We have tried water, very hot water on the suction table, 10%
ethanol in water, and alpha amylase solutions of 56-168 AU (although
it's possible that the enzyme we used was too old or requires pH
adjustments or other changes in the variables to make it effective).

I am familiar with the papers by Library of Congress staff from the
1990's which described removing silking from documents.   I would
appreciate any treatment suggestions, recommendations of currently
available alpha amylase enzymes, or observations on silking that
might lead to alternate treatment directions.

Ala Rekrut
Manager, Preservation Services
Archives of Manitoba


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                  Conservation DistList Instance 29:20
                 Distributed: Saturday, October 3, 2015
                       Message Id: cdl-29-20-012
                                  ***