White residue on leather

The Toronto Reference Library has four, full-bound leather books
from 1808 which are covered in white, circular streaks that appear
to be from a previous application of a leather dressing or
consolidant.  It is unknown when this dressing was applied, but it
is believed that it was prior to the 1980s.

The substance is hard and brittle. Under low magnification, it is
opaque, shiny and opalescent.  It appears to be somewhat
crystalline.

It has been difficult to find information in the conservation
literature which describes this type of residue.  Many treatments
for removing leather dressings focus upon the removal of a sticky or
creamy spue caused by the application of Neatsfoot oil or British
Museum Leather Dressing.   Other articles on wax "efflorescence" and
"crystalline bloom" describe fluffy or soft deposits.

We have been experimenting with methods to remove these streaks
without affecting the marbled calf leather below.  We have found
ethanol to be somewhat effective with the least amount of
disfiguration to the leather. However, it does not remove the
substance completely and we are concerned that this may only be
re-solubilizing the substance rather than removing it. We are
concerned about the long term effects of surface cleaning the
leather with ethanol and are ultimately concerned about the
reappearance of the white substance.

Any information on similar types of residue on leather and its
treatment would be welcome.

Laura Cunningham
Conservator
Preservation and Digitization Services
Toronto Reference Library
789 Yonge Street
Toronto, Ontario M4W 2G8


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                  Conservation DistList Instance 23:34
                 Distributed: Thursday, March 11, 2010
                       Message Id: cdl-23-34-023
                                  ***